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post #1 of 1 (permalink) Old 09-26-2016, 03:55 PM Thread Starter
Join Date: Sep 2016
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Cobalt AC/Heat Only Works on 4 High

My 2005 Chevrolet Cobalt AC/Heat only works correctly on the highest setting which is 4 on the dial. On 1, 2, and 3 it turns on like it should blow AC/Heat but is not normal more like running the fan only on 1 with no cold or hot air coming from the vents. So only the high setting of 4 works.

I replaced the "Resistor" under the passenger side dash board which resulted in virtually no change, it may have increased 123 settings minimally but still is not fixed. I say this because it seemed like it was doing better job at not working then the prior resistor but only minimally or just my imagination at work. Replaced the resistor with "AC Delco" GM# 15818910 (ACD# 15-80879). This step came from many people saying on forums that it is likely the Resistor as many Chevy Colorado owners had this issue and solved it with a new resistor.

I checked the 2 fuses in the center console fuse box behind the console kick panel and they are fine. This check was based on internet pictures of which fuses to check being the 2 two fuses in the box split by another fuse near the top.

I also pulled the "AC Clutch Fuse/Relay" in the fuse box under the hood and it seems to me to be o.k. I put a multimeter on 2 of its 4 prongs diagonally (2 are for power and 2 close the relay circuit) set the multimeter to "Ohms" and got what I think is correct readings of 87 and 0 (meaning it is not blown since it closes the circuit with the zero reading) and the relay shows "87" on the side of it. Any advice how to check this and be sure it is working?

Finally I used an AC refill Freon/refrigerant can and plugged it into the port under the hood. Ran the car to fill up the AC and that changed nothing. (I did read that Cobalts have an AC system that if it is low on freon/refrigerant then the entire system doesn't work correctly for some reason?) I don't know exactly just what I read.

So in conclusion. I have no idea if the relay is actually bad. What other fuses might not be working for 123 settings and so my only other option at this point is to rent a AC pressure gauge and see if the system is full/working. And I have no idea what the results of that will even mean.

I did also read that over time AC motors build up resistance and require more voltage and this can wear out the AC motor. So then is my motor only working on 4 because it is old. 2005 Cobalt with 80,000 miles living in hot Florida so it is used all the time. Thanks for the help on this.

---------- Post added at 10:55 PM ---------- Previous post was at 10:41 PM ----------

I also want to warn/caution that there is a similar looking relay in the fuse box under the hood that should not used to diagnose relay problems. It is the "Fuel Pump" relay/fuse. Do not pull that relay and replace it with the "AC Clutch Fuse/Relay" as it will make you car not work due to no fuel running. I read a post that said you can replace the AC Clutch Relay with the "Headlight Relay." On a 2005 Cobalt the only similar looking relay to the AC Clutch is the Fuel Pump Relay. So as far as I can tell there is no headlight relay that can replace the ac clutch relay.

Last edited by juneboat; 09-26-2016 at 03:44 PM.
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4 setting , air conditioning , heat , high , not working

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