Hi all,

I’ ve this issue when the air conditioning is on: the radiator fan won’t turn on. The mechanic told me the fan must kick in togheter the A/C system in order to cool down the gas inside the pipes. I checked the wiring scheme, and I’m searching for a dark blue wire that should turn the fan on. Where can Ifind that wire? I have a 1990 3.1 V6. Thanks in advance!

 

Have you checked the wiring for the cooling fan relay to be intact? When my fan switch failed i was able to turn on the AC to get me home. Granted the wiring is unmolested

 

Hi punkmaster98, I' m going to check it. When I bought the car some years ago, the whole wiring inside the car was terrible. I restored the original wiring and I think I'm done with it, but I' ll check the relay and wiring for sure.

Do you confirm the radiator fan must to be on with the A/C engaged?

Thanks!

 

Yes. The fan must run when the A/C is on.

 

 

Could be this thing related to the fan and A/C?

 

have you checked the fan relay?

 

what you have there is connector C105 if I am not mistaken, it is for a 90 305 TPI engine anyway. That connector melts. I don't know why, mine was at an early age. I've heard others report it as well. Here is the diagram of what is in that connector.

Not sure what your connector does, but the diagram below would not prevent fan from coming on unless it is preventing you AC from coming on. EDIT: The reason I say that, is because if the pressure switch is not connected, then I don't think your ac would turn on. but it would be worth checking connectivity on the pressure switch. maybe its intermittent. If you look at the ecm diagram in link below, the pressure switch will prevent fan from turning on, but the diagrams don't clearly state how they are wired (they just are)

EDIT: That may not be a melted C105, it may be special grease used to keep water out.

C105

 

Find the ECM diagram for your model, and you will find out what turns on the fan. Similar to this. https://www.thirdgen.org/forums/v6/4...ml#post3801073

In this example, it would either be the temp switch or the a/c pressure switch. Or a broken wire, or a bad fan, or relay.

 

Just did, the a/c relay as well. All seems to be ok. But recently I had to re-solder the fan relay wires, the previous owner installed an anti-theft system many years ago. So the wires worn through the years.

 

Great! The situation is more clearer now. I’ll check and I’ll update you guys. Thanks!

 

Maybe is this wire? I’ve a 1227730 ECM. Where I can find this gray wire under the hood in order to check continuity?

 

That is where these wiring diagrams get confusing. See if you can also find the wiring diagrams for the a/c system - that will also assist.

You might give it the old college try and see if there is continuity between the blue wire in C105 and the relay, input F. Or, if you're really brave, bypass F, and apply ground at this input, that would simulate everything needed to turn on the fan. I'd make damn sure you got the correct wiring diagram before proceeding with that. but if you do that, then all you are missing is the ECM to command it to turn on.

edit: IF YOU do try to by-pass F, make sure to take the wire off, otherwise you could damage the ECM

 

One other thing that I don't understand, is the ECM (I would guess) is reading these sensors, to determine if the A/C fan should be engaged. so if the sensors are bad, or not connected, you wont get the ECM command to turn on the fan. A data logger may help with this, I'm not sure what data comes thru on these cars.

 

I just swapped out the old chip with another one, I have the same problem. Now I' m gonna try as you suggested and I' ll tell you asap.

Thanks!

 

does your car have 2 fans? As far as I know, the 2nd fan should also turn on when water temp gets above a certain temp. easy way to test this is let your car idle while in park until temp climbs to max, you should see the 2nd fan turn on. if it doesn't, then that should help get you closer to identifying the problem.

 

Single fan

 

Then those example wiring diagrams above are definitely not for your car.

 

Thanks anyway, Liquid! made some progresses yesterday. I tested the system under the hood, it seems to work properly. Now I' m checking the HVAC controls, I think that' s something wrong with the slider connections. It' s like it' s always set on heater position, reason why the fan doesn' t start. The electrical system was heavily hijacked by the old owner, I think I' ll find some other surprises around...
About the HVAC, which is the wire behind the slider that selects the A/C and heater?

 

I know the A/C selection lever turns on the A/C. Not sure if this is vacuum operated or electrical. In 1990, some of the selectors on that control panel are vacuum operated, just don't recall what. Don't know much about the wiring, I'm learning myself right now, but since I'm working in this area of the car I've studied it a bit. I did notice on my setup, it uses the vacuum reserve somehow - may be to keep the vent doors open, don't recall and don't have my book on me. Look into that and make sure your vacuum reserve is connected. If you plan to keep the car, do yourself a favor and get a service manual. There may be a PDF version floating around the 3Gen board somewhere.

sounds like you are on the right track, sounds like the a/c isn't even working. you should hear/see the clutch engage. if not, there are some basic things you can check, like is the a/c clutch signal getting turned on? Same with other switches, are they on? Maybe your refrigerant is low and switches not turning on?

 

 

Its hard to find info on 3.1 because so few guys have them. This diagram for 92, Vin F/8. Looks like you could measure at connector C202 to see if it is getting signal. need to find this same diagram for your car.

EDIT: I was off, can't tell where to measure from this diagram. at C105 you could measure to see if there is signal there. Maybe at the presure cycle switch you could measure, its hard for me to read these diagrams, not sure how to read them. they are not traditional electrical engineer schematics that I am used to reading.

 

The fan a/c pressure switch in on the refrigerant line. Should be a dark blue and a black/white white on the terminal plug. When the a/c it turned on and the line pressure drops below 232ish psi, this switch opens and commands the ECM to run the fan because the a/c is on. Unplugging this, if everything else is in working order, should make the fan run at all times with the engine running.

 

This will be useful for sure! I just tried to unplug the connector and the fan didn't turn on. Maybe a problem on the dark blu wire?

Thanks

 

Does the fan come on if you try to retrieve trouble codes ? (It should)

https://www.obd-codes.com/faq/read-g...codes-free.php

 

Yes, it does

 

Listening in.

 

Granted, you're running a newer ECM than my 87 but, the v6 still operates very similar to the '87 TPI (electrically).. so, unplugging that FP switch may need to combine with another input. My 87, that blue wire not grounded (or plugged in) will cause my primary fan to run at key on and run, too.

So that shows the ECM is still able to control the fan relay (function as it should) and that the fan circuit is working back to the ECM. The only other electrical thing I can see is you may not be getting 12v power from the lt green/blk wire on the high pressure cutoff (back of compressor) to the ECM.

 

Thanks deadbird! I' ll check this thing also, I think there' s a huge hijacking work under the hood. Wish me luck!