'91 Park Ave. - Blower Won't Work on HI Speed Setting

[timrice]

Anybody else have this problem with their Parks? The symptom is that when you set the blower to its high speed setting, it may run for a while at that setting and then just stop. Or sometimes it won't run at all.

Last year when this happened, I dug into the wiring for the climate control center, and I found a really crusty, crispy wire in that circuit. Looked like it had gotten hot a lot in the past, and like someone else had already fixed it a time or two.

I repaired it by nipping off the bad spot, and reconnecting the two ends with a splice. Worked great for a quite a while, and now it's back again. Even cuts out some on the next lower setting, too.

I'm wondering if the wire GM used just wasn't a large enough wire to carry the current that's required.

Wouldn't be that big a deal if the fan moved enough air on the lower settings, but in my car, those settings are usually pretty worthless.

[timrice]

Well, the fan finally quit working altogether.

I cut all four of the wires (BRN, BLU, GRN, and ORG) that run into the back of the climate control module on the dash. These wires are for the blower fan setting. I got rid of the old connector which had a couple of terminals melted into it, and put in a new Weather-Pack connector and terminals.

In the course of doing this, I found that someone had already spliced in a bypass for the BRN wire that runs under the dash and connects to the BRN wire on the module. That wire is OK. It has battery voltage on it, and I'm guessing it supplies the fan speed selector switch. After getting the new connector installed, I hooked it back up, and it still didn't blow on any setting. I disconnected the module, and bridged the BRN wire to each of the three others, and I got the LOW setting to work that way, but not the higher two settings.

I then dug under the relay and fuse panel on the firewall under the hood and pulled out the "blower control module" (??) This is basically just a flat plate with a 4-way connector on it, and you have three different-sized wire windings (resistances), that daisy-chain between the terminals. I measured these at 0.4 ohms, 0.5 ohms, and 2.7 ohms. (The idea being to drop the voltage applied to the motor down to one degree or another from battery level, thus modulating the speed?) I saw no opens, shorts, or corrosion, and the module's connector and terminals were in good order. While I had this off, I noticed that the terminal on the dark blue wire going to this resistance module had apparently gotten hot and melt-welded itself to the connector (like some of the wires I'd found under the dash), so I couldn't extract it. Nor could I extract the light-blue one next to it, though I didn't see any evidence of heat. The third wire, light brown, had a terminal that was not making good contact, so I straightened it out, and voila--I got my medium setting back. At this point, I have everything but the highest speed.

What I'm wondering is if that melted dark blue wire is the right circuit to be checking for the problem with the high-speed setting. It goes to the relay just above on the firewall that I know is the blower motor relay. A year or two ago when I was working on this same problem, I *thought* I was able to put battery power on the orange wire on that relay and the fan would run on high. When I do that now, the relay clicks OK, but the fan doesn't go.

I'm thinking I've ruled out any problems with my climate control module or fan selector switch in the dash. I don't know yet if I have a bad blower motor relay, or if that melty blue wire is part of my problem, or just what. (Hope it's not the relay, these don't look very "replaceable" since they're not the blade-terminal style that plug into a socket or relay block.) If anyone knows how to service / replace those, let me know. I've popped the top off, but all you see is the relay coil, not the wire connections. This relay has a black, blue, and orange wire (all 18 AWG). It also has a larger purple and a larger red wire (14 or 16 AWG). No doubt the red is battery supply. The purple goes to the fan motor terminal. I'm guessing the black is the relay coil's ground. I'm not clear on the blue and orange wire functions yet. (Seems like I had this figured out once and drew it up--but I can't find my diagram.)

So does the high-speed circuit go through that resistor module at all, or does it just get full juice by activating that blower motor relay and putting battery voltage across the motor terminals?

I'm assuming the fan motor itself is OK, since it will work on the lower settings--I'd think it'd work if given full juice direct from the battery.

Any advice on the operation of this system in general is appreciated.

[Jed Rule]

The low blower speeds are controled thru the resistor assembly and (dark blue) feed to the blower relay. On high speed, the (orange wire) causes the blower relay to switch over and pick up power directly from fuse 3 underhood (red wire) rather than (dark blue) feed from the resistor assembly. The (purple) is the blower feed
Yes, GM has had a problem with fan blower controls and wiring for many years. The wire, connectors and controllers do not seem to hold up to the power draw and the overheated components often fail.

[timrice]

What Jed Rule says is correct. It's nice to see that what I learned today out in the shop being affirmed here. (As well as what I've suspected for two years now about GM's under-design of the blower electrical system.)

I have the problem fixed - all blower motor settings are working again. I actually had two problems to solve, not just one.

First thing today, I ruled out the blower motor itself by putting battery voltage across its terminals - it zipped right up on high, so no problem there.

Yesterday, I'd already cleaned up the ratty connections behind the climate control module in the dash and confirmed my resistor module was OK.

Then I started looking closer at the blower motor relay (3rd one from passenger side of Maxifuse/Relay panel on firewall in engine compartment). Reviewing my notes from two years back, I confirmed--as Jed Rule says--that if you put power on the orange wire, that should engage the relay and switch +12V onto the purple motor wire. Today, that wasn't happening, so the relay became strongly suspect. Yesterday, I had wanted to get that relay opened up, but I didn't know just how to do it. A bit of research revealed that when you've got the "lid" or "cap" off it, you just put a flat-blade screwdriver in the seam in the plastic--it's got little indentations on two sides apparently for that exact purpose--and pry it open. The five terminals are oriented in a couple different directions, so this takes a bit of work to wiggle it out. By the way, if you haven't disconnected your battery (-) terminal, do that first. Once the relay's pried free of this "socket" you can really see how it works, and you can see the terminal numbering clearly--they're stamped on the bottom of the relay where the blade terminals protrude. (That schematic stamped on the relay "lid" is worthless unless you're used to working with these relays every day.)

I left my notes and homemade drawings in the shop, but if memory serves, here's the blower motor relay pinout:

Orange - 85 (Signal from climate control module
fan switch; when you ask for HI speed, this signal switches to 12V, and it's the high side of the relay coil. When this wire has 12V on it, terminals 87 and 30 get connected. Otherwise, terminals 87a and 30 are connected.)

Black - 86 (Low side of relay coil - ground)

Purple - 30 (This is the wire that has one of four voltages on it, depending on which of the four fan speed settings you've selected. It goes to the blower motor's + terminal.)

Blue - 87a (This wire is the "output" of the resistor module tucked under the Maxifuse panel. It will have one of three voltages on it, each corresponding to one of the three lower fan speed settings, LO, Medium Low, or Medium HI. If the orange wire on 85 is not hot, the relay coil does not engage, and as a result, this blue wire is connected to the purple wire "output" on the 30 terminal, and thus you have one of your three intermediate voltages to the fan motor.)

Red - 87 (This is battery voltage all the time. If the orange wire goes hot, then the relay coil engages, pulls the relay in, and connects this terminal to the purple wire "output" on the 30 terminal, and thus you have max power to the fan motor.)

Basically, the low three fan speed settings don't require the relay to be engaged. But the highest setting does, and that's why the purple and the red wire are larger gauge--they have to carry more current.

Current means heat. Too much heat means things melt. Things like relay sockets. With the relay out, it became immediately obvious that the purple and red terminals had melt-welded themselves right into the connector. At this point, I had a good laugh at myself, because what I thought before was an external "spot weld" of the relay body and the relay socket at the seam turned out to be the melted socket plastic where the red wire had tried to burn through! Here I'd been afraid I would tear this socket up and when I finally had it apart, I saw I couldn't have done much to make it worse!!

I couldn't extract the purple and red terminals from the relay socket. These terminals are "pull to seat" style (that's good) which means they have to be extracted from the relay side of the socket. A small, narrow flat-blade screwdriver will probably work fine if you don't have a GM P/N 12094429 extraction tool handy. Not being able to get the melted terminals out, I left the other three terminals seated in the socket and decided to simply drill the purple and red ones out. I snipped these two wires just behind the relay socket. Once I had the two cavities drilled out, I pushed the purple and red wires back through the socket, stripped them, and crimped on some new terminals. With the drill-out method, there was no way these were going to seat properly, even if the pyroclastic flow hadn't ruined the seating surfaces first. But there was enough connector body integrity left that between the remaining plastic of the socket's cavity dividers, and the relay's terminals keeping them generally oriented, this would make a decent temporary fix. I say "temporary," because there's no reason to believe that this melting won't occur again in the future, and I don't want two terminals touching in there that shouldn't be.

To make this fix permanent, I will go to the local dealership this week and order a brand new socket and the correct relay terminals (the ones in my toolbox were "close," but not exact replacements) and do this right.

I checked the relay itself using a multimeter--it was fine. I cleaned the blade terminals and electromechanical contacts up carefully with some garnet paper. I plugged the relay back into the socket I'd just finished the root canal on, and put the lid back on it. I checked for HI fan speed, and I had it. I am sure the cause of failure here was the fact that the red wire had gotten hot enough that the plastic flowed and eventually coated the terminals to the point where no current would flow.

Way back at the beginning, I said I actually had two problems (well, if you don't count rambling on as a problem--some do). The bad terminals in the blower motor relay socket accounted for loss of HI speed.

The second problem was the loss of the lower speed settings. As I mentioned earlier in Post #2, I'd say this was due to either the ratty connections at the four-way connector directly behind the climate control module's fan speed selector switch (which I replaced altogether), or the poor mating force and glaze build-up of the terminals on the resistor module's connector. Possibly both.

Finally I got all the dash plastic and sound insulator panels put back in place. My compliments to GM for sticking to a 7mm fastener throughout, and for having relatively easy-to-remove dash and trim panels--that was nice, as opposed to the crappy fan motor wiring). I also thought it was neat that they put the resistor module coils down in the plenum to help keep them cool so the fan speed doesn't droop as you run it.

The summary lesson for me was this:

If you have a GM product with fan speed problems, the connection points are the weak link, and should be near the top of your list of things to check.

1) The blower motor relay socket
2) The 4-way resistor module connector
3) The 4-way connector coming out of the climate control module.

Discoloration of the wiring insulation near these connectors is a dead giveaway.

I will try to remember to post again when I have P/Ns for the "correct" terminals and the new relay socket.

All this work, and what do I have to show for it?
A car that blows.

[Jed Rule]

Hey I learned a new word today - pyroclastic.

[timrice]

Went to the dealership today to get a new relay socket to replace the burnt one. The P/N is PT153. It comes pre-terminated with the wires already crimped in, and you would have to butt-splice it in when you cut the old one off.

But don't bother. They wanted $48 for it. In the 10-15 milliseconds before I even got enraged over the egregious price-gouging, I was pre-miffed because the last thing I wanted in this fan circuit was more connections between the relay and motor. So I will go to the junkyard and snip one off the firewall of another 3.8 V6-bearing GM car, make sure it hasn't been melted too, and put new terminals in that.

Now my trip to the dealership was not a total waste, not by a longshot. I got to sniff the leather interior on a commemorative-edition Corvette, for one thing, and I made the mistake of asking how the fleur-de-lis [that lily-looking thing on the red flag...you've seen it] wound up being part of the 'vette logo, and I got a 10-min. lecture on the history of that from the sales guy. I was impressed with the level of detail (or just plain BS) he had to offer on it.

After I was through carping about the $48 for a little square of molded plastic, the parts man said: "a lot of times the wires get hot because of the blower motor getting old--it ought to run in the 9-15 amp range."

That got me to thinking...I just assumed that even though I cleaned up the wiring yesterday, that this would eventually happen again because GM under-designed the wiring capacity. And I *still* say they under-designed it, but I resolved to find out what current *my* fan actually drew. Where I work, we have one of those clamp-over style current detectors that you can plug into a digital multimeter, so I borrowed it. Here are the numbers I came up with:

23 to 25 A on "HI"
13 to 15 A on the next lowest setting, "MED-HI."

And this circuit is fused for 25A! (Fuse #17) So I've been pushing the envelope on current draw, probably for some time now. And the 13-15 A draw on the MED-HI setting is probably why I saw some toasty-looking spots around the connections on the dark blue wire under the dash. It doesn't have to carry as much current, but remember that one's 18-gauge, so it doesn't have as much current capacity as the 16-gauge wire that runs the HI setting, either. I wonder how much good the fuse really does--25 A is a lot of current to ask of 16-gauge wiring, especially when the terminations are blade-type and not soldered. (Anybody out there have your blower circuit fuse burn out and fix it by replacing the blower motor?) In *my* car, the "fuse" turned out to be the wiring and the terminals, not the fuse in the fuse block.

With these high currents measured on my '91 Park and duly recorded, I popped the hood on my '90 LeSabre (same blower motor) which I put a new blower in about 16K mi. ago. On "HI" setting, it only drew 14 A, which was in the parts-man's "spec." As another data point, I measured the draw on my '95 LeSabre (still has its original blower motor), and it drew 21 A on "HI." And the purple motor wire on it looks wimpier than the 16-gauge on my Park Ave.

I made the decision then to go get a new blower motor and put it in the Park Ave. I got that put in tonight. It was a bit of a pain--you have to take off the bar between the strut towers and pull the firewall-side motor hook off to get the clearance you need to get the blower out. At any rate, the new motor only needed 17 A on "HI" and just 9 A on "MED HI." A significant current reduction (17 vs. 25 A), and one that should keep the wiring a bit cooler for a while. Now I'm considering getting a new blower for the '95 before *its* wiring fries...if it's not already too late.

I would like to know what GM's published spec is for the fan's current draw; who knows if the parts man recalled it accurately? What I *do* know is that getting the same or better air flow for 6-8 amps less current seems like a good thing.

Hey, GM--maybe what we need is a "Replace Blower Motor Soon" light that comes on when the fan starts drawing enough current to start slow-roasting the wiring.

My recommendation is that if you're having blower circuit problems, check to see how much current your fan's drawing--it may be a factor.

Forgive me for the off-the-wall words, Jed. You can thank my 11th-grade English teacher for that. She was a vocabulary fanatic, and scarred some of us permanently. If only I'd paid as much attention in Auto Shop class...

So did you get the dictionary out and look it up? If you dig "pyroclastic," you'll *really* like "lahar," one of the lesser-known and oft-underrated natural disasters.

[DioGreer]

Wow, thanks for the detailed essay there . Makes me want to go out and check the current draw on the blower motor on my 91 PA.

I have had experience with blower motors in the past. I used to drive a 1986 olds cutlass supreme, and I had to replace the blower motor for a different reason. Water had leaked into the motor and caused it to corrode and wobble. For a couple of months I would hit the right side of the dashboard to stop the blower from wobbling. Eventually I put in a new blower and all was well. The motor was installed from the top and had nothing in the way to make installation a pain.

My parents used to drive a 92 cadillac deville and they had a similar problem to what you had; the high speed blower wasnt working. We replaced the blower control module (located in the plenum accessible from the engine compartment) and it worked fine. No melted wires, etc. Maybe that fan was on its last leg as well. We didnt keep that car long enough to find out.

[timrice]

I would like to post a correction to my statement in Post #6 where I said that the fan blower motor circuit is fused for 25A. There *is* a 25A fuse in the fuse panel that flips down from under the LH-side dash, but that protects the wiring to the climate control module. There is a 30A Maxifuse on the firewall panel just above the blower motor relay that protects the A/C system and the battery supply wire to the blower relay. That's why I wasn't quite blowing the fuse when the fan was drawing 25A.

I still say 25A continuous is way too much to be running through a 16-gauge wire.

This past weekend, I got the replacement relay socket from the salvage yard installed, so everything is fixed "right," and with the lower current draw, I expect the blower motor to run well for a couple years or more, at which point I will check it before it has a chance to melt anything again.

[Clay_Bee]

Hello, I'm new to this forum.

I have a 91 PA in which the bower moteor won't come on. The blower is good, as I can direct short it to the battery and it turns. The compressor is cycleing, and the dashmount control appears to be operating properly.

I have checked the two fuses under the dash (10 amp driverside, and I think it was a 30 amp on the passenger side). A post at a different site said to replace that unit that adjusts voltage from the temperature of the evaporator housing (on firewall, in evaporator housing) but I'm not getting power to that unit from under dash.

Mu questions to you: Am I missing a fuse? I have heard of a 3-amp fuse on this system, but am clueless where to look.

What logical steps should I take to begin repairing this system? I've got a vlt-ohm meter, and the willingness to learn how to do this.

Thanks,

Clay

[Clay_Bee]

Sorry! I'll proofread more closely next time.

[timrice]

Welcome, Clay_Bee. As far as fuses for this system go, I know of only two.
One is the 25-Amp fuse in the pull-down block under the dash just below and left of the steering column. I believe that's the one that protects your climate control module and the in-dash wiring for that and the three lower-speed blower settings. The other is the green "A/C" 30-Amp fuse in the Maxifuse / Relay center along the firewall under the hood. I believe it protects your A/C wiring and the wiring for the highest-speed blower setting. If that green 30-Amp fuse is blown, I don't believe your A/C compressor would be engaging (I don't know that for certain), so it's probably OK, but it's so quick and easy to check, you should do it. You don't even have to pull those fuses out to check them— set your meter for "audible continuity check" so it will beep if you have a good circuit, and put your meter leads on the little test points that are exposed on the body of the fuses just for that purpose. You can check every fuse in the panel in 30 seconds that way.

One thing that you can easily check: With the hood up, turn your key switch to "on," but don't start the engine. Move your fan speed selector to "high." If you don't hear the fan blower motor relay click on and off when you move the selector to high and back, that's a problem right there. On my '91 PA, this relay is the third one over in the string of relays in the Maxifuse / Relay center if you start counting with "1" as the relay closest to the A/C accumulator. It will have five wires running into the back of it. (Don't cut yourself pulling these relays off their retainer clips—I learned that lesson at the salvage yard the other day.) A black, orange, blue (all smaller-gauge) and a fatter red and fatter purple wire. In Post #4 above, I explain what all these wires do. Note that a number of these relays in the Relay center have the same P/N, and are thus interchangeable, at least for temporary diagnostic purposes. So if you suspect the relay might be bad, just swap it with a neighboring relay to confirm it before you go get a replacement.

That resistor module that hangs down in the air plenum is such a simple device, I'd be surprised if yours was bad. A visual inspection and a simple resistance check with the unit out of the car is all you need to do there. (See info in Post #2 for details) Just move the Maxifuse / Relay center over far enough to get at the tiny little screws that fasten it down. Check the integrity of the four terminals in its connector (you can see above that I had problems there). Make sure there aren't any obvious open circuits in the module, either in the wire coils themselves, or at any of the terminals. Again, this is easily and quickly done with your voltmeter. Three of the wires to this module are "speed selection inputs" that come from your climate control module's fan speed setting, and the fourth is the "output" that goes the fan blower motor relay. When that relay is not engaged (i.e. whenever you have one of the lowest three speed settings selected), the output voltage of the resistor module is what is going to the fan motor. When the relay is engaged, the resistor module is not even part of the circuit anymore—the relay just puts full battery voltage on the motor (fat red wire gets switched to connect to the fat purple wire).

If you have not yet checked your under-dash wiring, I think you should make that your first priority, especially since you said you don't think you're getting any power to your resistor module. I'm guessing you have basically the same problem I had—the blower motor got old, and starting drawing too much current, and your wiring has gotten burnt and crispy. You need to find out how much current that fan is drawing when you put battery voltage on it. If it's up in the 22 to 25-Amp range, I'd replace it after finding and fixing the other problems. In my case, a tired blower motor was the root cause, and the heat-damaged wiring and relay socket were just the symptoms. (At first, I thought those things were the root cause, but as usual, I was wrong at first.)

Now in my Park Ave., there's a pale yellow wire (yours might be tan or brown—mine had already been replaced by somebody before I owned the car, as I later found out) that runs from that fuse 17 on the lower LH side in the pull-down panel along the dash to the climate control module. I found "hot spots" in that wire near the climate control module. Also, I found "hot spots" in the four-way plastic connector just behind the climate control module (CCM). I found toasted spots in the blue wire there, too. Anywhere there's a connector or a wire terminal, look close. Get a penlight flashlight so you can see down into those connectors and get a good close look for melted plastic, crispy copper, and discolored wiring insulation. I cut that connector out altogether and put in another one. To replace it, you could go to the dealership and order it out of their catalog or snip one out of a salvage car and butt-splice it into your system. All my crispy, ratty wiring was within just a few inches of the CCM (and that 4-way connector—I believe it's 4-way) and right at the relay socket where the blower motor relay plugs in. Since someone had already run a power splice to my CCM from the #17 fuse, you should check that whole length of wire in your car—that's highly suspect for your situation.

To get a really good look at the wiring behind the CCM, remove the ashtray. I also removed the fake wood trim panels (gentle prying), the glove box, the full-length face dash trim panel, etc. This lets you get the CCM out of the front of the dash and gives you access to the wiring from above instead of below and behind the dash. There's a lot of screws to remove, but a small cordless screwdriver and a 7mm socket make this a joy.

So in order, the things I would do are:
Check your fuses
Check for the blower motor relay "click."
Check your blower motor relay's connector for
signs of heat.
Check your under-dash CCM wiring and connectors for signs of heat.

I have a pretty good feeling you'll find something obvious very soon. Let us know what turns up!

[Clay_Bee]

Thanks Tim! Call me Clay. I'll start by following your procedure. When the fan went out, it was running on high speed during a hot day, and the fan stopped just as surely as if a fuse had blown. The blower motor had been making a small amount of intermittent bearing noise, so I replaced it right off the bat. Your comments have me very suspicious about the wiring.

I had it apart previously, as you suggested in your post, just to try and find fuses. Those seemed good, as did the relays, so I was at a loss. These are such great old cars, I had thought of maybe wiring a relay and 4-position switch to get the fan going, since everything else appears to be working at this time.

When you talk about the climate control module (CCM), what does that look like? Is that the dash unit with the controls?

[timrice]

I don't know if "CCM" is GM's acronym for it or not--I was just trying to shorten up my posting a bit--but yes, what I'm calling the CCM is that dash unit with the buttons and selector switches on it. It will come out of the dash as a unit if you get all the dash pieces off that obstruct your access to its mounting screws. You need to check all the wiring coming out of the back of that module on the side closest to the steering column. Any wire going into or out of that black four-way connector should be inspected. You may not be getting any power from the #17 fuse under the LH-side dash over to your CCM's fan speed selector. (Like I said, someone had already completely replaced that wire in my car before I owned it, and their "fix" turned out to be merely temporary.)

I'm glad to hear you already have a new fan in. That should mean you can dispense with the "how much current is it drawing" questions.

If your fan quit while it was on the highest speed setting, that tends to rule out the resistor module as a possible cause. It should only be involved with the lowest three of the four settings.

Good luck!!

[milltown12]

I have what seems to be the opposite problem with my 89 PA blower in that it runs all the time. This began suddenly and the only way to turn it off is to unplug the wire assembly from the blower. I have read the previous posts and don't know whether the 89 and 91 are similar but I can't find a relay that seems appropriate. I went to NAPA and asked for a blower relay and they gave me something but I can't find where it should go.

I did find a heat sink type thing that sits flush on the firewall from the top. When the right plug is removed, the blower stops (purple.black wire)

Any thoughts?
Thanks

[public]

Glad to find this thread. I have a similar problem with my 98 Century. I have a post over there but no replies so far. I did notice that the blade connectors on the resistor module are all the same size "too F@%&in small" The high speed wire did the melt down thing but the harness is no longer available from GM. They did tell me the price was $147.00. I guess it is going to be Weather Pac's for me. Like you said at least it is easy to get to. Could this be a fire hazard?? Mine was really burnt, I turned it off when I smelled smoke. The motor and the resistor are new. Too bad one for a Toyota won't fit!!! Those things never seem to break.