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Discussion Starter #1
Hi - my parents came to visit me and when they got here, they said they had no AC for the trip, it was 100 degrees out.

Being the great son that I am, I took out my 134a gauges and tested the AC pressures. The high side started climbing, low side was low. So I then looked at the engine fan, it was not blowing so condensor was not doing its job... OK.

Jumping right in, I ordered a new fan motor and got that today. Swapped it out, but then it still didn't work. I guess I should have tested the fan motor resistance first. That turned out to be okay at around 1 ohm. I tested the resistor in the fan shroud and that seems ok... low resistance that would not stop the fan from going.

I then tested to see if I had power at the plug going into the fan shroud, coming off the fuse box... NO POWER.

I pulled off the fuse box cover, just left of the fan and started checking the relays and the fuses. I see 3 relays for the Fan (Lo, High and S/P, which is series/parallel), so this is a 3 speed blower config, I guess controlled by the ECM or PCM. I only found two fuses and they tested good. Is there a 3rd fuse?

I see I am getting 14v power on two pins of the S/P and High relay, getting 14v and I believe 3v to the Low relay.

I have connectivity from the relays to the fan shroud plug, but never get any power over to the plug.

I am stumped!!!! Please help. I need to get them out of here, LOL...
 

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Forgot to mention, also had the P2601 error code, which I have since cleared, maybe thinking this was preventing the fan from kicking.

However, with the AC turned on the fan must come on instantly to start condensing the refridgerant. Ugh.
 

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Been out there in the heat still trying to figure it out. Seems like something is just not kicking power on to the relays... I idled and revved the car, car gets hot, but not overheat on the temp gauge and the fan still just does not spin at all. Before it would spin very little when the car was hot and engine revved up. Hard to imagine the ECM would knock out the fan that would basically stop the car being able to be driven. I tried to jump it with 12v from the battery, but the resistance on the fan motor itself being 0.9 ohm was too low, seemed like a it was shorting. So stopped that attempt to just hot wire it and let them get home with the fan running full bore, LOL.
 

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I was able to connect 12 volt to the upper left pin of the low and high relays (the one that has connectivity to the plug and fan motor. When I did this, I got the fan to operate on low and high speeds, but still not luck getting the car to trigger the relays. I know the relay is good b/c I swapped them around...

Why would car not energize these relays... No luck, so now car is going to have to go to the shop. Ugh! What a disappointment!
 

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2008 STS-V, 2008 STS AWD
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Here's the only schematic of the cooling fans in the shop book:

585345

Here's the block diagram:
585347

There are three different systems, one, two and three fans and several pages of diagnostics using OBD2 codes. On the 6 cylinder engine there is a temperature sensor next to the oil dipstick.
 

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Discussion Starter #6
Thanks.

I guess its something else... some other input thats preventing it from closing the relays. He will just bring it to cadillac tomorrow... what a disappointment on my end, LOL. Ive had my BMW X5 18 years and never once brought it to the shop. I had to replace my engine fan a few years back, so thought it was definitely that. I didn't swap the Aux Water Pump which seems to be related to the P2601 code, but man why would they kill the engine fan even if that were the case. All seems rather odd.

He drove the car to me 100 miles and the thing didn't overheat. However, I wont let him drive back with that fan, not working. Ill let you all know what get replace on the car when I get it back from the dealer... I dont even want to see that bill.

Good night!
 

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Discussion Starter #7
So like I said, I was able to jump the fan motor using the 12 volt from the battery and it turned on both low and high speed. Fan motor was good.

Brought it to the dealer. They took it right in and diagnosed it. They said the AC was low on refridgerant and that the fan wont kick on unless the system has some minimum pressure. This was the first thing I tested and I guess I just didn't know what I was reading when reading the pressures on my gauges. It seemed to me like the system had pressure. The high side was increasing, but I think it was just compressing air and a little 134a. The low side was low, like 32psi, which isnt really that low... thats why I thought my system was okay and had charge.

The AC was filled in June, and today the dealer said the system was vacuumed and leak tested, and tested ok, so very odd that the gas would have got out quickly. it wasnt like the AC got weak and then off, it just went off. so very odd. My buddy who works on AC for a living said, he has seen where the car test okay when its sitting stopped, but there might be a cracked pipe at the elbow and when you drive or hit a pothole it will leak out under pressure.

Anyway - my parents were gone on schedule... $230 spent at the dealer...
 
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