Stumped

Alright, need an outsiders view on this one. The problem, whacked out cooling fan (single fan) on a '85 Z, 305 TPI vin F.

All started with no temp gauge reading. Replaced the sending unit and wiring (alot of wiring on this car was hacked up by the previous owner) and the gauge was restored and operational.

Shortly there after, the fan went dead in terms of "normal operation", but switching the a/c on would cycle it.

Not too long after, this was no longer working either. No fan operation what so ever. Jumping power to it, fan runs, so it's ok.

This weekend, I replaced the CTS (pain in the rear it is) and relay (mounted on radiator post).

First attempt:

Fan came on at around 150*(?), ran for a minute, then never came on again. A/c wouldn't trip at all.

Do some back pedalling:

Fuse labeled "fan / FP" (10A, shouldn't it be a 20A?) blown. Replace fuse, try again, nothing.

Continuity check of wiring, all ok. Still nothing.

Aggravated as all hell, gave up and went about my holiday weekend to deal with it some other time.

Came back out to roll windows up, and for the giggles, started the motor, cold at this point, and the damn fan came right on, ran for a couple of minuites, then shut off again? Almost like when the ECM is in diagnotstic mode but longer?

Can't find any specific diagrams for the 85, TPI with a single fan. According to the '86 there is a seperate "fan switch" which I would think to be the culpret, located between cyls 6 & 8. Nothing there?

Now I bought the switch anyway that WAS listed for an '85. Where the hell is it?

Can't find any specific diagrams for the 85, TPI with a single fan. According to the '86 there is a seperate "fan switch" which I would think to be the culpret, located between cyls 6 & 8. Nothing there?

Now I bought the switch anyway that WAS listed for an '85. Where the hell is it?
Return the switch, the fan on the 85's is controlled strictly by the ECM. Check and clean all of your grounds (there's a grounding point on the back of each cylinder head) If this doesn't help, send me your E mail address and I'll send you the schematics for that car.

Thanks Morley, now I feel better, that's exactly what I thought, it should be ECM controlled by input of the CTS right?

I'll check out the rest of the grounds. What I did do is track the ground wire from the fan to it's body mount behind the battery as a means of continuity check.

I'm really wondering now about the fuse panel being all wrong too.

If the wiring was hacked up that badly, send your E mail addy and I'll send you the schematics...sounds like you may really need them.

Hey Morley,

Well, things have gotten a little more interesting with the situation.

Up until today, last night actually, this car always fired up and ran, flawlessly, even in 10* weather. Now all of the sudden, when cold, it will crank over, struggle to stay alive then die. Bear in mind I currently don't dirve it every day not very practical/economical for my commute, so I have to work with what my wife tells me happened. She also indicated that out of nowhere on the way home last night it "lost alot of power".

Based on how far she was away, I can only assume that it lost power when it went into closed loop. ???

So, this morning, before I go to work I go to check out her complaint that "it feels like a spark plug wire came off". They are fine. Fire the motor, barely catches, sputters, dies. Repeat a few times, same procedure, same result. So, finally getting aggravated I goose the throttle to keep it living, and it does, AND, low and behold, the damn fan is running, continually. Still trying to varify the loss of power complaint, goose the throttle a couple of times, and there is a lag in throttle response, kind of like no advance OR delayed fuel pump response (remember my phantom fuse "fan/FP"?).

So, in curiosity, I cut the motor off. Restart, fires right up. Idle seems different, goose throttle, lag in repsonse is gone? Oh, and the fan has gone dead again (which it s/b at this temp).

Shut it off and refire. Idle has changed back to the first run, lag in throttle response returns, and the damn fan is cycling now???WTF???

If you look at the link I gave you yesterday or the general schematic for that fact, here's what I find, but can't figure why these new problems, combined with the fan are intermittent, one start there, next start gone.

G119 (ground I believe near firewall or head) we have grounded together, MAF, MAF burnoff relay (hard start?), fan pressure switch, fuel pump relay, and ESC module ("loss of power" complaint?)

I'm not a electircal genious here, but would you go with the ground situation here, of the phantom Fan/FP fuse?

Yes, clean all of the grounds, I know the 2 on the back of the heads are a royal pain, but they are most often the problem when it comes to grounds.
To getthe nuts off of those studs I took a 14mm el cheapo socket and drilled 2 holes in it (4 actually) all the way through it. Now I can put the socket on the nut and use a small metal bar (stout music wire) to turn the socket since you can't get a wrench on the RH one and there is no way a ratchet is going on it.

If that doesn't cure the start, sputter die and loss of power, clean the throttle body and TPS with valvoline syntec carb and throttle body cleaner, this stuff eats carbon like a kid with candy.
Last resort is to try a new AC Delco ignition module, if that doesn't fix it, keep the module they always go out when you don't have a spare.

If that doesn't cure the start, sputter die and loss of power, clean the throttle body and TPS with valvoline syntec carb and throttle body cleaner, this stuff eats carbon like a kid with candy.
Last resort is to try a new AC Delco ignition module, if that doesn't fix it, keep the module they always go out when you don't have a spare.

Throttle body is clean as whistle, tps set iac, and set screw are correct. I prefer hogwash over the valvoline,, the valvoline IS good, but hogwash reacts almost instantaniously without scrubbing, especially handy on those pesky quadrajet carb linkages that tend to always bind up.

Modules are in abundance, if I have to buy a new one, I always buy em in quantity (atleast 2 or 3 and none of the aftermarket brands either, striaght to delco, fired enough to know). And when scouting the boneyards I always seem to have a few more in my tool bag then I went in with?

I'm confident that the ground (G118) is the culpret. Did alot of searching the net yesterday on it. Starts off from around the battery feed, then runs up the right side fram rail, then over to the left side head, why in the hell GM woudn't just put it on the right head is beyond me. But all of the conditions fit. There was a guy on TGO that took almost 9 months to figure out a MAF problem of constant DTC 33 & 34. I don't have any codes, which is scarry, I would think that if the ESC loses connection it would throw a code.

Anyway, thanks for the input. I probably won't get to it until sunday. But, I'll definately let you know of the result, can't stand when people don't reply a solved problem. I'm not the best electircal guy around. And have alot of "unique" tools for odd spaces.

'

Morley,

It's alive! Cleaned off the gournds, still didn't work, put the ECM in diagnotsic mode to make sure it was live and kicking and wouln't you know fan came on, along with DTC 43. So traced the splice to ground and the ESC ground wire was cracked and hitting the power feed for the wiper motor. Resolved that and a crack spot in the wiring for the CTS buried under the alternator and viola, it runs.

Not very happy tho, waits until 240 to kick on (according to the guage) and only drops it back to 220 at idle. Was going to see how it did in driving airflow but, now I have to deal with determining why the plug for cyl 5 keeps fouling, looks like a bad injector at this point.