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Howdy Gents, first post here, i came into a 95 Formula A4 car a month or two back, low miles (though it appears to have sat in a field for a decade or so) and decent mechanically. I've been working out all the niggles i could find so far but i'm stumped.
At the moment, my cooling fans start up the moment i start the car (warm or cold start), though i don't remember it doing this when i first got it. I changed the relays with no change, then downloaded Gary's excellent Scan9495 which shows my coolant temp at a pretty constant 180-190 degrees (which agrees with the gauge). I'm fairly sure the fans shouldn't come on until well into the 200's, but it never even gets there, i've just got the fans on 80 or 90 percent of the time (sometimes they switch off for a bit after sustained freeway speeds). I was thinking i would have a DTC or a temp sensor that's way off, but that's not the case. Any thoughts on where to look or next steps?
-Thanks ahead of time for any help
Last edited by Jaxem; 09-27-2014 at 09:44 PM.
Reason: More specific Title
The relays operate by virtue of grounds put out by the PCM. You might want to check the wiring for any alterations from the previous owner. If there are no DTCs, there should be no reason they come on at startup. Does the scan program have an indicator for fan status?
Yes, the program shows when the relays are energized and which fans should be going at what speed, it's showing up correctly as they cycle from low to high and sometimes off, it even has a section where you can command them to the speed you want, and they shut right off when that's how i set them, so it seems like the correct grounds are being set to do what i tell the PCM to do...i wonder if maybe the PCM itself is messed up.
Also, the car was/is pretty much bone stock. i've mostly just been replacing bits and fluids the most involved thing so far being plugs and wires, but i haven't touched any wiring so far
Fans should operate when the A/C system is turned on. Could possibly have something to do with that. Maybe something wrong with the wiring in the A/C system.
I thought that could be the case too, but if i use Scan 9495 to monitor the AC system, it correctly shows the AC request, correctly switches the fans on (after i've manually switched them off), and shows a normal pressure...The thing that's got me confused, is that if there was just a short somewhere, i shouldn't be able to command the fans to all the different speeds just fine from the diagnostic program. If there's an extra ground somewhere, it should stay grounded and they should never turn off, but when i tell them to (via Scan 9495) they do...i'm going to start digging through the wiring this weekend regardless since i really don't want to burn the fans out just ignoring the issue, but i'm not hopeful
I thought that could be the case too, but if i use Scan 9495 to monitor the AC system, it correctly shows the AC request, correctly switches the fans on (after i've manually switched them off), and shows a normal pressure...The thing that's got me confused, is that if there was just a short somewhere, i shouldn't be able to command the fans to all the different speeds just fine from the diagnostic program. If there's an extra ground somewhere, it should stay grounded and they should never turn off, but when i tell them to (via Scan 9495) they do...i'm going to start digging through the wiring this weekend regardless since i really don't want to burn the fans out just ignoring the issue, but i'm not hopeful
I had the same problem with my 96 Trans Am bro. What I did was I bought a Fan relay switch. Then I ran the wire inside the cabin. (Previously my fans wouldn't come on at all. I went to the junkyard got some relays off a V6 4th Gen Camaro and it somewhat fixed the problem. Only difference is the fans would finally come on at 210F) When I bought my fan relay switch it fixed my problem! It stays right now between 160F & 180F During the day & at night. However since I live in Las Vegas & it gets really hot here so sometimes during 1:00-2:00pm the temperature of my car goes in between 180F and 210F at the most. I plan on changing my temperature stat soon though. If it works for me living in the dessert it'll work for you. Here's the link so you can see it for yourself and in case you want to buy it. http://www.speedinc.com/shop-by-vehi...02-f-body.html
Quick update, i've only had a bit of time to inspect wiring (broke a tranny mount, which took precedence), but it so far all looks good. Just on a long shot, here's some screenshots of the car hot and cold, does anyone see anything in all this that could explain the fans going on? I'm under the impression that coolant temp is the single variable that should control it...
so the PCM is telling the fans to be on all the time. I am kinda stumped here. All the signals would say no fans, but the fans are ON...did you try just swapping the relays?
Shbox would know, but I am confident that the ECU looks at the same sensor that displays the temp on the gauge/ecu for fan operation right? I always forget.
In this case, maybe the ECU is shot? Probably not a relay issue, because if it was a bad relay, the ECU would say NO FANS and fans would be on anyway
so the PCM is telling the fans to be on all the time. I am kinda stumped here. All the signals would say no fans, but the fans are ON...did you try just swapping the relays?
Shbox would know, but I am confident that the ECU looks at the same sensor that displays the temp on the gauge/ecu for fan operation right? I always forget.
In this case, maybe the ECU is shot? Probably not a relay issue, because if it was a bad relay, the ECU would say NO FANS and fans would be on anyway
First thing i tried was putting new relays in, i can even switch the fans on and off from the pictured software, so the PCM correctly controls them...but also thinks they need to be on. I'm starting to lean towards the PCM as well, but don't really want to replace it unless absolutely necessary.
It seems strange though that everything else runs as it should, but just the fans are messed up. If the PCM went bad, i would think it would cause a whole mess of problems...
So i was cruising similar threads and came across this posted by El Cid on this thread I know it's not for a Firebird, or even an LT1, but i wonder if it might apply since the setup sounds very similar:
Don't know if this will help:
Cooling Fan Control 3.8L and 5.3L
The engine cooling fan system consists of 2 electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G100.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the fan 2 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the fan 2 relay and the fan 3 relay through the high speed cooling fan relay control circuit. This energizes the fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed. The 5.3L LS4 cooling fan is not affected by engine speed.
The 3.8L L26 and L32 cooling fan is affected only if the cooling fan is commanded on for A/C pressure. If coolant temperature is commanding the cooling fans on low or high speed, engine speed does not affect the cooling fan operation.
The following are conditions that can affect the cooling fan:
• Engine speed above 49 mph will cancel the A/C pressure high speed cooling fan request.
• Engine speed above 55 mph will cancel the A/C pressure high and low speed cooling fan request.
The PCM commands Low Speed Fans on under the following conditions:
• Engine coolant temperature exceeds approximately 100°C (212°F)
• When air conditioning (A/C) is requested and the ambient temperature is more than 4°C (39°F)
• After the vehicle is shut off if the engine coolant temperature at key-off is more than 117°C (242°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.
The PCM commands High Speed Fans on under the following conditions:
• Engine coolant temperature exceeds approximately 105°C (221°F)
Looking at the Scan 9495 screen shots i posted above, my A/C refrigerant pressure is pretty much always above 180 psi...This looks like it could be a possible root cause, can someone please confirm that this switches the fans on? It'd be nice to not have to swap my PCM...perhaps i just need a new pressure sensor or to bleed off some A/C pressure. Anyone chime in on what my A/C pressure should be?
Just a shot but if the cooling temp sensor is bad it will kick the fans on high all the time, I would also check that
Yeah, the sensor is ok i'm pretty sure, the temp the PCM and gauge are showing agree, and it seems like ~185 would be spot on for where the temp would be with the t-stat open and the fans going all the time.
I have another thought though, my outside air blows curiously cold (like as cold as when i have A/C turned on) so i never use the A/C. There's a bit of noise that comes from the area of the compressor that could be the clutch...if the clutch isn't fully disengaging and the A/C is running all the time (hence the weirdly cool vent temps) would that raise the A/C pressure possibly resulting in fans always running?...I posted just above about the possibility of excessive A/C pressure switching fans on...let me know what you think guys, i should be getting a PCM to swap in soon, so that'll be another thing to strike from the possible cause list.
So it's confirmed, the AC clutch is stuck and that's been causing my fan issue, i'll be pulling it off a little later this week and will update with results. Thanks for the input and suggestions everyone!
So it's confirmed, the AC clutch is stuck and that's been causing my fan issue, i'll be pulling it off a little later this week and will update with results. Thanks for the input and suggestions everyone!
Nice. I like how it says clutch status is off also haha. Surprised you didn't notice the clutch was on before
09-04-2014, 01:45 PM
Cooling fans stuck on 
