A/C Condenser Fan/Wiring Issue, and a TPS Question...

[MouthForWar]

I've got a new one for you guys.

The weather just started to heated up around here finally, so I began running the A/C in my '92 K1500 (5.7). Well, she started overheating (220+) when running the A/C at idle for ten minutes or more. After going through all the usual diagnostics (compressor, fan clutch, etc.), I discovered the cause...

...the previous owner deleted the freaking condenser/aux fan and replaced it with the passenger side horn.

Yes, you read that correctly. The horn. They relocated the passenger side horn to right in front of the radiator, and removed the condenser fan altogether. Why they did any of this, I don't know.

But, here's my problem....the wiring and the correct connector for the aux fan isn't there. I have no idea where it is. Another condenser fan is only like $80, so I'm not worried about that. But I need to know which color wires I'm looking for (so I can maybe trace where they were cut), and what specific female 2-pin connector I'm looking for...so once I order it, I can wire it in.

There is a pair of wires in the passenger side of the engine bay, black and orange, that run back to the relay block, with an old corroded connector that wasn't plugged in to anything...but it doesn't reach the front of the truck where the fan is. So idk. There are no other wires or connectors that I can see that are unused/terminated/disconnected, but again, I have no idea what colors I'm looking for so that I can maybe start looking from the other end.

Edit: I also can't find the relay or the switch, and I need the mounting bolts, which do not come with the new assemblies and I can't find anywhere. Ugh.


Also, completely unrelated side question....has anyone ever had a bad TPS sensor cause an engine to straight up cut out/die, randomly, while driving? Thing died twice on me today while driving. No rhyme or reason. This is also on top of an occasionally rough idle/stumble that has reappeared. TPS is one of the few remaining things I haven't replaced and is our next best guess....as we've gone through a lot of other things to no avail.

Help! Lol.

 

[SAATR]

There is no reason that your truck should overheat at idle with the AC running unless there is an issue with the cooling system. The vast majority of these trucks never had an electric aux fan, and I have personally never seen one factory installed on a 1500. In this instance, an electric fan would only be a bandaid for a bigger cooling issue elsewhere in the system. The best way I know to begin diagnosis without obvious issues is to check the temperature differential across the radiator at operating temp. Five degrees or less from inlet to outlet and you have a cooling capacity issue, ie poor airflow through the radiator, fan not working properly, undersized radiator, etc. More than ten degrees and you have a flow issue, ie internally plugged radiator, faulty water pump, thermostat stuck closed or barely flowing coolant, etc. An infrared thermometer can be your best friend in this situation.

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[MouthForWar]

I have personally never seen one factory installed on a 1500.

In all fairness, the FSM, AllData, Chilton's, every GM parts site, etc. all say there's supposed to be a condenser fan, and the mounting holes are exactly where they should be. Plus, they're a dime a dozen, and GM still lists the original part. Additionally, this delete, and relocation of the horn, was very obviously intentional and very shade-tree-esque. This truck was definitely intentionally built with a condenser fan. Whether it needs it or not is up for debate I suppose, but it was there, it was deleted, and I would like to restore it. I'm just looking for someone to tell me what color the stock wiring for it is so I can trace where the PO cut it....and maybe find the harness and mounting bolts. I'm a stickler for restoring stuff to the way it's supposed to be. Lol. And in this instance, I truly feel it would solve my issue.

If we want to delve into cooling diagnosis anyway, though, by all means: In my experience, cooling issues usually manifest themselves in other circumstances as well. But the thing is, I can rod that thing until kingdom come, on a hot day, and then let it idle for forever on hot pavement (without A/C obviously), and it stays within 180-200. I can also run the A/C until kingdom come as long as the vehicle is moving 15+mph, and it stays within 180-200. I could run that thing off of a cliff and have it explode in a nuclear fireball and it would probably stay at 180-200. Literally the only thing that pushes the truck over the edge is idling, on a hot day, with the A/C running, for over 10 minutes after it hits operating temp. Which is precisely the circumstance that the condenser fan is designed/there for, imho.

But anyway, continuing on: the thermostat (180 degree stat) is good, fan clutch is engaging, intake mani gasket was just done (along with the corresponding coolant drain/refill). Coolant temp sensors are also new (I was chasing a different issue there), and the A/C compressor itself is fine: no noise and plenty of cold air. No leaks at the water pump, and all hoses are fully pressurizing at operating temp and beyond. Also, no coolant leaks elsewhere and no white smoke from the exhaust, so nothing [major] is burning off internally. Radiator is the correct version/size (it's the version with the oil cooler, just as a side note...which I do know did not come on all of these trucks.). Some fins are damaged but no worse than what's on the average older vehicle. If we want to go even further into the abyss, the oil is new (no unnecessary or extreme friction/heat causation there). I mean, I can point a heat gun at stuff just to make absolute sure, but I'd really rather just put the condenser fan back where it goes, like was originally intended (again, I'm a stickler for restoring stuff to the way it's supposed to be, especially when there's a problem that would obviously be solved by doing so) and see where that puts me.

Plus, I truly don't believe that with everything above checking out, that such a miniscule unknown problem (if it exists) would cause the temp to climb 20-30 degrees (possibly more, but I kill it before it gets that far...I don't want to deal with warped heads or any of that nonsense) in such a specific, extreme circumstance...but not in any others. A blockage of that magnitude (either stuck thermostat, radiator or hose blockage, what have you), for example, would prevent hoses from fully pressurizing..not to mention that the temps would be an issue in a greater variety of circumstances. A fan clutch that is still adequately engaging (as it currently is) would not be so far gone as to cause that much of a temp increase. A compressor that has that much resistance (and is creating that much more heat) would not be silent, nor would it continue to produce ice-cold air (as it still does). Etc. Idk man; I'm just saying we've been pretty thorough so far. If you have any other ideas, by all means...but I would still like to replace the deleted condenser fan that's supposed to be there in the first place. I'm not sure how to explain it, but stuff like that really bugs me. Always has. Even if this thing never gets hot again, it's gonna bug me.

 

[df2x4]

Go ahead and install the fan if you want to, but it's nothing to do with your overheating issue. Like @SAATR said, the aux fan was a very uncommon option to begin with. My Suburban has nearly every option available including the cold weather package with all the aux coolers, but it doesn't have the aux fan. Most trucks, especially half tons, never had one.

You've got a cooling system issue somewhere. You say you've checked it all, but I'd check it again. And do what he said, check the temps with an infrared thermometer. I bet your radiator has a partial clog somewhere or your water pump is on the way out. You can still have pressure in the hoses if that's the case.

 

[77Impala]

My 89 does not have the aux fan, nor does it need it even though I live in Texas. On most of the vehicles I have had the coolant temp would rise a few degrees with the AC on but not with this truck. I even checked it with my thermal temp gun to verify that my sensor or gauge was not malfunctioning.

I am also leaning on a cooling issue with your truck. I know that you can run that engine without AC and it never overheats no matter what load you put on it. But with AC on your engine is pulling the heat being released from the AC condenser through the radiator which is already trying to remove the heat from the engine. This added heat will put a additional load on the engine's ability to remove it own heat. That said I have replaced several radiators that could keep up by them selves but could not keep up with the AC. And a handful of those were on vehicle that my customers had already replaced the thermostat and/or water pump. That is due to to many passages in the radiator being clogged up and not able to handle the additional load.

How old is your radiator? Might want to consider replacing it.

 

[89RCLB]

Agree with 77Impala and df2x4 on the cooling issue...

As for the aux fan, my '91 C2500 parts truck has an aux fan but no idea if it is factory. Ground wire comes from the inner right hand fender next to the battery and through the core support to the fan. The other wire (black with what looks like a green tracer) is run through the front harness up to near the firewall to a single weather pack connector and continues on into the engine harness. HTH.

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Edit: Looking at it again, someone ran the ground wire from the inner right hand fender and tied into the ground lead ahead of the weather pack connector at the fan. The original ground wire is run through the loom over to the passenger side headlights, breaks out of the loom and goes to the inner fender. Not sure why this was done as I continuity tested the fround wire and it was fine...shrug. Hope this all makes sense.

 

[SAATR]

If you haven't already, try using compressed air to blow back through the radiator from the fan side. Dirt and debris tend to accumulate in the fins and can cause airflow issues that could affect cooling when there is a smaller temperature differential between the coolant and the cooling air, such as when the air conditioner is operating.

As far as the fan goes, all electrical schematics I have been able to find for an auxiliary fan reference a 2500/3500 or a 7.4L equipped 1500. It your truck had one, you should still have a thermostatic switch in the passenger side cylinder head for controlling the fan, and of course the bespoke relay that you have been unable to locate. There should also be a fuse specifically for that circuit in your fuse panel. If there is no fuse and the fuse block location was not ever wired for a fuse to be installed in that location, I'd say you either had an NSA level wiping of all traces of said fan, or there was never one there in the first place. I also maintain that none of this is germane to your overheating issue, but whatever blows your skirt up.

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[magimerlin]

Take the 180 thermo out and put the 195 stock temp back in... the extra load is the a/c at idle. The motor temp hits 180 and opens the thermostat letting the cooler coolant back to the motor and the hotter into the radiator to cool off. With a 180 thermostat it doesnt have time to cool back off in the radiator. So the coolant going back into the motor that is suppose to be cooler is in fact heating up and staying hotter each cycle.. after the coolant gets to 180 on both sides of the thermostat it just stays open.. no time for cooling going on, just keeps getting hotter and hotter.... then bam.... overheating...



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[magimerlin]

And as mentioned.... spray your condensor and radiator out.. and how did you test your fan clutch?

 

[magimerlin]

As far as the wiring color goes..... you mentioned ALLDATA... just look up the wiring schematic since you mentioned it I assume you have access to it.. FSM and Chilton both have the wire diagrams in then aswell...

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