91 Park Blower Motor Control Module

I have a 91 PA with Auto A/C. I have no blower fan on any setting. The flaps in the plenum operate when operating the HVAC from the dash controls. All of my wires appear good. And I appear to have appropriate voltage to the dash CCM. I suspect I may have a bad Blower Motor Control Module (BMCM). This sets in the engine compartment behind the Relay Center. On cars without Auto A/C it is called a “Blower Resistor Assembly.”

My question is: How do I tell if the BMCM is good? On another site, a poster indicated that this is the weak link in this system, and can be saved by putting a fuse inline to the blower (which seems reasonable given the draw of older blower motors).

There are two plugs on the BMCM. The first plug has a heavy Red wire with 11.82v at its terminal. There is a second unused position on this plug. The other plug has Purple to the fan (at 1.62v. I assume this is coming from under the dash, as the Purple “Ys” before going to the Blower); a Grey w/BlkStripe wire at 7.6v; and a Black wire at .02v (I think this is error, and the Blk is the Grnd….but, I measured this on the Med speed setting, on High this voltage went to .01). There is a 4th unused position on this plug.

My assumption is that the 7.6v from the Greyw/BlkStrpe should be going to the Blower, but it is not. I also think that this switches to high blower speed by switching through the Purple and Red primary wire when it gets a signal from the Dash CCM? Maybe a relay?

Any ideas on how I should proceed?

Checked the Blower Motor Control Module again. The Red wire is hot with Battery voltage at all times. The Purple blower fan has no voltage at any time. The Greyw/BlkStrip has 7.5v when the dash Command Computer is turned on, and to any fan speed setting. The Black has .02v at all times.

I am thinking this module is at least a small part of the problem. Does anyone have a wiring diagram showing where these wires get their inputs? I have a Haynes that is pretty good for the big stuff, but is limited for this problem.

Does anyone know anything about the relays under the passenger side kick panel, and their respective purposes? Haynes is showing a Hi/Low and Blower Fan relay. There are 8 or so of the same relays on this center.

I had the same problem with my 91 PA about a year ago. The problem was the blower control module. I got another one from a local "junk yard", plugged it in and it has worked fine since then. I had to ask a mechanic where the module was, you are a good sleuth to locate it.

I have a fairly complete 1991 Park Ave. wiring diagram that I can copy for you, if you want it. I sold my PA about a month ago and bought a 1998 PA. They are great cars tha can be found cheap when used.

Hello STM,

Thanks for the kind offer of the wiring diagram. I'll take you up on it! How do you want to get in touch?

I ordered my module from Autopartsgiant.com. Part number 15-72530. The big pain is that GM does not have a single parts system at dealerships. One dealership could not find the part or its location, had no clue what I was talking about, and even indicated that the part didn't exist. Another gave me the wrong part number, and quoted twice the price as Autopartsgiant. Another was 150% of APG.

Calling APG, they gave me a url www.acdelco.com (http://www.acdelco.com/html/catalog/index_img.htm). Select Parts Catalog, Display Image By Catalog Number. Put the part number in. Visual confirmation that this is the part I needed before even ordering!

Check your Private messages near the top & on the right

More info on the 1991 Park Ave. blower control module used with the electronic climate control.
There are no blower relays nor resistors as the control module performs all the relay & speed control functions via a large transistor or SCR. If the module fails, the blower generally will not work at all.

FYI: The relays at the passenger kick panel area are for accesories and the fuel pump. I have a complete (& possibly accurate) list if you need this info.

I have a 90 PA. The fan control SCR (silicon control rectifier), which is a big transistor, failed. Not cheap new. Later had fan fail. The simplest way to determine if it is a fan or SCR failure is to power the fan directly temporarily.

Thanks gerakela. I have a new fan on it. Tim Rice and Jed Rule have an outstanding set of posts on the subject of fans if you haven't read it yet. It makes me think I should fuse the new BMCM when I put it in.

STM: I see in post #6 where you mention there aren't blower relays or resistors in '91 Park Avenues. My '91 PA must be an exception, as the connector for my firewall-mounted blower relay melted down, and in the course of troubleshooting, I checked the resistor module (three crude wire springs tacked to a metal panel) located just below the relay in the air plenum. (See related thread in this forum.)

Any chance my PA was an early '91 build and GM changed the design partway through the '91 model year?

91 PA With Excellent Blower Fan

Hello All,

The BMCM arrived, is installed, and there were 0 left over screws. The module did the trick, and there was absolutely no need to do anything but pull the relay center forward and measure the red wire (hot side) to see of it was powered, and then the purple wire to see if there was sufficient votage to power-up the blower fan.

As I understand, the PA has 3 possible systems for 91. Mine is full auto. There is also a split in the VIN for that year, no doubt are early and late year models of the 91.

If you have full auto, assess the BMCM first.

Thanks for your help Sidney, and everyone else on this thread. Until the next time we meet, and the case is sol-ved.

That is *great* news, Clay. Way to go.

I'm glad to hear about the three different systems for managing the blower on that model. It means STM and I aren't crazy. I'm pretty sure mine has the minimum feature "slider switches" design.

My previous post regarding the electronic blower speed control was for vehicles that have the electronic AC controls which have cool & warm buttons & display set temperature and outside temp. The typical way of blower speed control on millions of vehicles is via relays and blower cooled resistor coils. They are not as fragile as they may appear.

One thing to remember is that 12 volt systems require a lot of amps compared to the 120 volt ac systems in our homes. So a 240 watt blower in a car will require 240w/12v= 20 amps, but a hypothetical similarly powered blower in your house would require only 240w/120v= 2 amps. This is why wires can get so hot and things sometimes melt in vehicle electrical systems. More amperes need bigger wires and more robust connectors and relays. Direct Current which is used in cars is also much more prone to arcing (than AC) when something goes awry. Arcing often causes melting.

By The Way: LeSabres (particularly the "Limited" models share many key components with the PA and until 1997 were practically identical mechanically and electrically (not 100% and not as good quality seats, etc.)