A/C Problem

[kd5hge]

I just bought an '04 with 105K. I don't know the history of it as it was bought from a dealer. When I test drove it, it was about 60 degrees out and rainy. The a/c seemed to work well then but since it was so cool out, I may have been fooled. Now that it is getting to the 90's, the a/c isn't keeping up. It works well when the truck is moving but if you sit still, like at a light, it blows warm. I can hear the compressor kicking on and off in about 5 second intervals. I put a gauge on the low side and found that when the compressor is on, I get a reading of 50psi which, from my past experience is about right, but when the compressor kicks off, the pressure spikes upto 100-150 psi! I know this isn't right! The condenser lines are both very hot. I can hardly touch them with out burning my finger. I put a gauge on my two company trucks (1 '03 and 1 '06) and they both sit around 50 psi. The compressor on the two work trucks doesn't kick off and the pressure doesn't spike. I have some a/c experience but not a bunch. Any help you can give would be much appriciated by me and the soon to be wife!

 

[jakprince]

It sounds to me like the fan may not be engaging like it should. You should be able to hear it roaring with the ac on and it idling.

 

[kd5hge]

That may be it. I know it is engaging but, now that you mention it, it doesn't roar like the other two trucks... I've never had a fan clutch that failed like that. I'll change it out and see what happens... Thanks...

 

[MMeier]

Did you check for codes? Right now my 03 has P0647... A/C clutch relay voltage high... went through the flow charts, but can not seem to figure out whats wrong with the thing yet. I have to shut off the a/C and then turn it back on to keep it cool inside, anyone else experience this one yet?

 

[TWenske]

The spike is normal, when the compressor kicks off the high side and the low side equalize pressure. 50 psi seems high to me. How hot was it outside when you checked it? What was the high side pressure when right before the compressor kicked off?

 

[kd5hge]

I forgot to check the high side. The outside temp was about 85-90 degrees. I am just confused because in our other trucks, if the fan clutch isn't engaged, the a/c still blows cold. I know this because we leave them running for hours on location an the a/c still blows cold even on still days. I know with my 01, I have to point it into the wind to keep it blowing cold but even with no breeze it will still blow cool air. The '04, which is the one with the problem, blows warm air almost instantly when you stop moving.

 

[BJMarshall]

Isn't there a reflash for this that changes the way the fan engages? I know on the 03 when I got the Smarty for it, it changed the way the fan worked.

 

[CumminsDoofus]

Any help you can give would be much appriciated by me and the soon to be wife!

Here ya go,... ..... My only advice is that she shouldn't marry a dude that can only afford a 2004 with 105,000 miles :-laf



You get this figgered out yet, Ya Goof?... ... You rode around in that 94 fer years with the winder's down and the only thing that wrong was it need a can of freon. LOL



If you get tired of fartin' with it, bring it down here and I'll look at it

 

[Missouri Mule]

kd5hge, compressor should not cut in and out every 5 seconds. Symptoms of low freon but faulty low pressure cycling switch,faulty high pressure switch and maybe bad compressor clutch coukld cause this probelm.

Both lines should not be hot. Will have to check to see what line is supposed to be hot or you can check on one of your other trucks.

 

[BGarofalo]

In my 03 I have this same code P0647. My AC will work fine for a while and then it will kick off and on. Then I have to turn the AC off and turn it back on for it to work and that doesnt last long. Anybody have any ideas? I dont see this as being a coolant level problem because it will blow cold air for an hour before it shuts down.

 

[Matt400]

I can hear the compressor kicking on and off in about 5 second intervals.

If it never did get this software update-

TSB 18-003-04



then its probably just low on system charge.