I am currently working on my wife's 2004 Chevy Impala LS. 3.8 V6 with 202K. This started with the fact that my wife's AC was not blowing cold air. I hooked manifild gauges and found that both high and low side pressures were low, making me think that it was low on coolant. I added leak detector dye to the system and by the time I was going to add refrigerant, the coolant was boiling back up into the resevoir. I immediatly shut down the car. No coolant in the oil, no wetness on passenger side floor. After checking the thermostat (195), it did not open until after water rapidly boiling (and opened barely). I flushed the system, installed a new cap and thermostat (180). Now I filled the system and got it up to temp, and noticed that the cooling fans did not come on at all. Would not turn on with AC on or heater. All fuses checked out OK, but did not test relays, as it was getting dark. I also noticed that while on heat, the driver's side air was not very hot, neither side was cold on AC. I have also (within the last sevearl months) replaced the coolant temp sensor and rear O2 sensor, trying to get rid of engine light code (to no avail) have not had it scanned recently. I know that this is a lot of information and I'm not sure if they are all related or not, but wanted to give everything. Please help, this thing is driving me crazy.
FIRST CHECK THE UNDER HOOD JUNCTION BLOCK FUSES. 2 25A FUSES FAN CONTROLE ONE AND FAN CONTROLE 2&3. SEE IF THERE IS VOLTAGE ON THE LT BLU WIRE AND THE GRY @ THE 2 FAN MOTORS. TRY ADDING POWER ON THEM AND SEE IF THAY RUN VERIFY GOOD GROUNDS ON THE ONE BLACK WIRE. IF YOU CAN GET A SCANER IT WOULD HELP ALOT WE WILL WANT TO CHECK TO SEE IF THERE IS A AC REQUEST AND FAN COMAND. THAN TRY TO RUN THE FANS WITH THE OUT PUT COMAND. @ THE ECM IN THE AIR CLEANER KEY ON TRY TO GROUND THE DK BLU AND DK GRN @ PINS 5 AND 6. THIS WILL RUN THE FANS LOW AND HO SPEED.
July, 11, 2012 AT 1:39 AM
So when you turn the ac on does the ac clutch kick in and the compressor start spining in the center of the ac clutch?Have you checked the cooling fan fuses yet?Also were the fans on when the coolant was boiling over?Do you know what temp it was boiling over at?
July, 11, 2012 AT 1:52 AM
I will put a meter on it tomorrow and verify power. I did test fuses, everything was good. Did not test relays. I don't have access to a good scanner, jsut test light and voltmeter. As for the compressor, it does kick on and spins (not forzen up), but still no fan. I could not say for sure that the fans came on last night or not. The dash board temp gauge was reading over half, I would estimate 220-230, which is high for this car (usually doesn't get half way). I almost forgot. About a month ago the car overheated due to loosing coolant, I ended up renting a hauler and towing it home. I tried to limp it, but it was not gonna happen, coolant was everywhere. One of the plastic elbows rotted away by the water pump and needed replaced. I replaced both elbows, refilled and burped the system. AC worked at that time.
July, 11, 2012 AT 1:58 AM
The a/c compressor will be shut down by the ECM if the engine temp is to hi
July, 11, 2012 AT 10:45 PM
Ok, here is what I have found out so far. Both fans will power on when jumped directy to the battery. Both fans will come on if the tempature control sensor. I do not show any volts at the white wire or light blue wire, at fan plug ends. Key off, I have power on #85 for all three relays & #30 on relays, 1 & 3, 13 volts. Car running power on #85 & #30 on all three relays, 14 volts. Power on #87 on 2 & 3 & #87a, 17 volts. Also found. Key off, IF apply test light to #86 on #1 relay both fans come on low. IF apply test light to #86 on #3 relay pass side fan comes on. Clicking sounds when using test light to said leads. Burned my fingers trying to test #2 relay, nothing to report.
July, 11, 2012 AT 10:52 PM
When you speak of the BCM, I'm wondering if this may be the root of the problem, although I'm not ready to run out and buy one (ouch pricey). I know that intermitantley, the security light will come on and then the car will not start. Wait a while and bingo, it starts. I've been told that the BCM controls the pass lock as well. Maybe I'm over thinking, but just asking. I've also been told how to bypass the pass lock and just haven't done it yet.
July, 11, 2012 AT 11:52 PM
Tried to make sure that I had no air in the system, so I ran the car up to temp. Neither fan came on, coolant bubbling back out of filler neck so I decided to shut off car. Bad idea. Coolant launched out of filler neck. After refilling and replacing cap I started the car and hosed off engine and got a quick whine noise (like a belt whine, but deeper tone), but went away quickly. As car ran, temp got to almost half way, no fans and coolant started boiling back into resevior and more whining this time. Whinig continued after shutting the car off. I could not identify if the whine was coming from boiling coolant of possibly something else. I hope this helps diagnose the problem and just doesn't add more confusion to an otherwise frustrating problem. Thanks.
July, 12, 2012 AT 12:11 AM
Its looking like the ecm is not grounding the relays. We will need a scaner to go deaped in to it.
July, 12, 2012 AT 12:23 AM
Ok, but I don't have access to a scanner anymore. Is there anyway to diagnose this porblem without the use of a scanner? I know that if I go to Auto Zone, they will just use a low end scanner that will not be albe to make any commands. Is this (ECM)an explination for the coolant backing up into the resevior?
July, 12, 2012 AT 12:35 AM
If the fans don't turn on and the engine temp is gettint hot the coolant will back up. The pcm turns on low speed @ 217 f and hi speed @230 f