My cooling fans are intermittently kicking on and my A/C is not working at idle because of it. I pulled the relays and jumpered cooling 1 relay and the left fan kicked on at high speed. Then I jumped cooling 2 relay and both fans kicked on at low speed. I took a mutimeter and measured from ground to the coil pin of the relay and got 13v. I tried switching relays and bending the pins a little incase the socket wasn’t making a connection but it still didn’t work. I checked the main ground right under the accumulator and it was fine. Is there another ground for the relays? Or is it not working because the high speed is burned out of the right fan?
01 STS no cooling fans
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Hmmm, no one wants to tackle this one...
Any codes?
Fan speed is controlled by the relays, not the fan itself. There are actually 3 relays, and 2 fan fuses... fan 1 low speed, fan 2 high speed, and a series/parallel (S/P) relay which controls the speed for both. They're all in the underhood fuse block.
Have you verified the PCM is getting the correct temp signal via scan tool from the coolant temp sensor? (it's right below the EGR valve.)
Joe
Any codes?
Fan speed is controlled by the relays, not the fan itself. There are actually 3 relays, and 2 fan fuses... fan 1 low speed, fan 2 high speed, and a series/parallel (S/P) relay which controls the speed for both. They're all in the underhood fuse block.
Have you verified the PCM is getting the correct temp signal via scan tool from the coolant temp sensor? (it's right below the EGR valve.)
Joe
No I don’t have any codes or a scan tool. I finally ordered the correct cooling fan assembly from rock auto but I don’t know if it will make it here by the weekend. I know the cooling fan 1 &2 relays are good but I don’t know about the third one. I wanted to make sure both fans speeds were working first.
You don't need a scan tool. The function is already built into the car. Read the "sticky" thread at the top of a couple of these main Forum pages - "How to pull codes". You want to scroll down to the OBD-II sequences.
The cooling fans should cycle on and off in slow, while in traffic, without A/C commanded. They go to slow at 224 degrees and fast at 235 or so. Any A/C function should set fans in slow at any time the A/C is ordered on. fans generally never run over 45 mph.
If your A/C is not working at idle only you may have a low freon charge or compressor/discharge temperature fault. You may find a code on that one.
Fan 1 low speed relay, Fan 2 high speed relay, Relay to series the fans to drop voltage so both fans run slow. (The relay titles are a bit misleading, because when the parallel-series relay drops out, both fans go to high speed. When it closes, they both go to low speed. The motors do not have their own built-in speeds - that's controlled by the parallel-series voltage drop.)
The cooling fans should cycle on and off in slow, while in traffic, without A/C commanded. They go to slow at 224 degrees and fast at 235 or so. Any A/C function should set fans in slow at any time the A/C is ordered on. fans generally never run over 45 mph.
If your A/C is not working at idle only you may have a low freon charge or compressor/discharge temperature fault. You may find a code on that one.
Fan 1 low speed relay, Fan 2 high speed relay, Relay to series the fans to drop voltage so both fans run slow. (The relay titles are a bit misleading, because when the parallel-series relay drops out, both fans go to high speed. When it closes, they both go to low speed. The motors do not have their own built-in speeds - that's controlled by the parallel-series voltage drop.)
If that’s the case I probably didn’t need to order the $114 fan. I thought maybe the fans had separate windings for high and low speed. Because when I removed the 1 & 2 relays and jumpered them individually both fans came on for low speed but only one came on at high speed. When the A/C is on at idle the relay coil for low speed has voltage but the relay doesn’t pull in that’s why I thought I had an open ground.
Rock Auto will surely have a return policy as long as the package isn't opened.
After reading this wiring diagram I see why only one fan would turn on with only the high speed relay jumpered. I need to find this 3rd speed control relay and jumper it as well for both fans. None of this explains why the fans will not turn on at all with the A/C on at idle.
To find out if the fan control problem is not in the fans themselves but in an A/C control circuit, you'll have to return the fan circuits to stock. Nothing involving the fans or A/C will ever work correctly until you do.
The A/C circuits tell the PCM to command "fans - ON", not the fan relays and circuits. The A/C system sends an identical command to the PCM as the one sent when engine temp reaches 224 degrees: "Fans - Slow". You have now bypassed that function, so you have no idea of what's wrong.
Diagnose the A/C, not the fans. See the little rectangular box labeled "Engine Controls Schematics" in the lower left of my diagram ? That's the culprit, not the fan circuits.
The A/C circuits tell the PCM to command "fans - ON", not the fan relays and circuits. The A/C system sends an identical command to the PCM as the one sent when engine temp reaches 224 degrees: "Fans - Slow". You have now bypassed that function, so you have no idea of what's wrong.
Diagnose the A/C, not the fans. See the little rectangular box labeled "Engine Controls Schematics" in the lower left of my diagram ? That's the culprit, not the fan circuits.
I agree, I just got side tracked when I only seen on fan kick on for high speed. What do you recommend for troubleshooting the A/C control circuit? When the A/C is turned on it looks like it should also pull in the fans at the same time. I'm going to go pull my codes again and see if I missed something.
OK so I was playing around bypassing my fan relays this weekend and I got both fans to work on low and high. I then tried the A/C in “auto” and “manual” mode and the fans did not turn engage on ether setting. Could my A/C power module be bad? Shouldn’t I get a code if it were?
Not sure about the code set for this one, but I would assume one should set. Somehow the PCM is not getting a "fans - on" command from the A/C system. The fix will involve some intense troubleshooting of the electrical system, using the factory wiring diagrams.
It may be as simple as a fuse associated with the A/C system or as expensive as some module. Maybe there's a relay malfunction.
Take a look at www.alldatadiy.com and see if their factory manuals and diagrams fill your needs.
It may be as simple as a fuse associated with the A/C system or as expensive as some module. Maybe there's a relay malfunction.
Take a look at www.alldatadiy.com and see if their factory manuals and diagrams fill your needs.
I'm having the same trouble with my 97 sts. No code associated with any of this codes I get are ipc- b1552, u1255, mmm-b2146, b2144 and rss-c1738.
In the message center I get very low refridgerant, ac compressor off. Would this make a difference?
No fans ever kick on. I have them wired to a switch and the switch to the maxi cooling fan fuse. I only do this as I have to get to work and it keeps it from overheating. I also can only get 1 fan (passenger side) to come on high speed. I cannot get drivers side to kick on and I have even replaced the fan. Nothing.
In the message center I get very low refridgerant, ac compressor off. Would this make a difference?
No fans ever kick on. I have them wired to a switch and the switch to the maxi cooling fan fuse. I only do this as I have to get to work and it keeps it from overheating. I also can only get 1 fan (passenger side) to come on high speed. I cannot get drivers side to kick on and I have even replaced the fan. Nothing.
Better figure out what is causing the overheating. This is just a bandaid that won't last forever.
The fans were working a few weeks ago. Car never overheated. It was getting hot one day (3/4) the way up gauge, I pulled over and looked in motor, fans were not on. If they were on it wouln't be getting hot. Right? It don't over heat if I use the fans occasiolly like the car should be.
No signs of hg failure, water pump, fan relays, thermostat, cts all have been replaced.
I do notice the fan relay on the far drivers side of the 3 the wire covering was removed where it leads into the relay connector. Something someone did? What is this relay used for?
No signs of hg failure, water pump, fan relays, thermostat, cts all have been replaced.
I do notice the fan relay on the far drivers side of the 3 the wire covering was removed where it leads into the relay connector. Something someone did? What is this relay used for?
My fans come on when the engine temp call for it just not when the A/C compressor kicks on. It’s leading me to think it the A/C power module or the Climate controller itself that’s not sending the signal to turn on the fans. I'm still fishing though the wiring diagrams.
VTSTS, Although the 2000+ engines, the subject of this thread, have a different relay/fuse setup in the engine compartment fuse box instead of on a separate board such as yours, the principles are the same: The PCM/ECM commands fans to either slow or fast, relaying commands from other modules. The fans are relay-set to series operation for slow - then the fans run at about 9.5 volts. The fans are set to parallel operation for fast - each fan receives full system voltage. The three relays are Fan 1, Fan 2 fast and Fans Series/Parallel. Sooooooo......if 1 & 2 are commanded ON slow, Fan 1 relay closes and the S/P relay is also closed so both fans run on the same circuit. Fast, the S/P relay drops out and Fan 2 relay closes and each fan gets full voltage.
This is for 2000+..........
This is for 2000+..........
Fixed my fans. It turns out the fans were fine it was the rebuilt compressor I installed. It was not getting to 199psi and that is why my cooling fans never came on. I replaced the compressor with an AC delco one and the A/C works fine.
Good report..............So the fans are NOT automatically commanded ON by a PCM signal that the A/C switch is ON.........they come on in response to the signal that the system is actually working.
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