Any GMC HVAC guys on here?

It got a filter/dryer/accumulator. The gauge Ports are before and after the orifice tube if remember. I think we just got low output from the compressor like stated above.


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Just read link from 1st post. If low side is pulling to 0 either restriction or low charge. Psi you should be seeing is around 35 low and 180ish hi. It's the compressor shut off when the low cycling switch was hot wired it's a definite restriction most likely from the compressor chitting itself.
 
6.6lEater said:
Just read link from 1st post. If low side is pulling to 0 either restriction or low charge. Psi you should be seeing is around 35 low and 180ish hi. It's the compressor shut off when the low cycling switch was hot wired it's a definite restriction most likely from the compressor chitting itself.
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it's not pulling to zero, he must have fat fingered his post. At idle with compressor engaged we saw consistent 100 on the high side and 90-95 on the low side. So we know the pressures are all jacked up. The question is what is driving it. When the low side switch was hot wired the compressor seemed to cycle a little longer than it did when it was not hot wired but not much longer. The compressor was kicking on and off pretty quickly. I assume b/c the low side pressure is all effed up? It looks like there are several TSBs out on this system that pertain to an accumulator but who knows. Most of the gmc/chevy dealerships around here are tarded and don't know what they are doing.
 
Refrigerant pressure sensor could cause this. You would need a scan tool to see data. It's the 3 wire sensor on the compressor discharge hose or on the compressor it's self. It will shut down compressor clutch if it sees 400+ hi side psi.
 
6.6lEater said:
Refrigerant pressure sensor could cause this. You would need a scan tool to see data. It's the 3 wire sensor on the compressor discharge hose or on the compressor it's self. It will shut down compressor clutch if it sees 400+ hi side psi.
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Not going anywhere near 400 on high side?
 
You have 5 feet of hose and a condenser before the high side service port. You still don't know what the ecm is seeing.
 
I do commercial HVAC. With that said if the clutch is staying engaged then the compressor is shot because its not pumping. The 5 psi difference you are seeing is likely in the gauges. If the clutch is coming in and out quickly then you have a issue with the low pressure sensor or wiring because you have plenty of refrigerant to keep the clutch engaged, and also likely a faulty compressor still as the suction pressure will very quickly drop if the compressor is ok and clutch is engages. I would figure out what the ecm is seeing because ultimately it controls the clutch based off what the sensors and snowflake button tells it to do.
 
I know you guys are talking CCOT system but is everyone certain that's what this is and not an expansion system? Just gathering info.


I agree on needing to see what the controls see.

If you have forced the compressor to function with no change in pressure, its shot IMO.

I lolled at the post about the pressure ports. Yes, in a very universal way, that is sound logic.



From my Not-So-Smart phone
 
Hmmm-so take it to gm dealership and have them put a tech 2 on it? I can just picture the mouth breather telling me its my flux capacitor right now....
 
Ultimately you are going to have to take it to someone that has the tools to do the job, especially if you have to open the system. One question is is the compressor clutch itself turning off after a few seconds of operating with the cycling switch bypassed? You can hot wire the compressor clutch to stay engaged by jumping terminal 87 to 30 where the ac relay goes into the fuse block. 5 seconds of operation of the compressor isn't enough to see what is happening. If it's a restriction, which is what I'm leaning towards, feel the lines of the compressor the smaller if the 2 is your high psi side. It should be hot to the touch, the higher the psi the hotter it is and vice versa. If at any point you feel a change in temp that is the restriction. Between the 2 service ports is the orfiace tube where psi/temp changes.
 
Well I don't exactly do the whole mouth breathing thing......

Reading threw all the posts, with your findings and what has been suggested it sounds low on charge or the compressor/clutch has given up. You not seeing any sort of sign of a leak does not mean it will not be low on charge. I think the rule of thumb is 10% loss of charge in a year. 2005 truck should take 1.6 maybe 1.8 pounds? 8-10% over the past 8 years.

The 6.6lEater+ guy you have been kind kicking around has just as many certifications as I and has been working in the stalls next to me for the past 11 years. I would not count anything he has to say out. I would put him up against any driveabillity, electrical, auto transmission tech in Merica and would win. I'm the smash and grab heavy line guy in our dealership. Guess what I'm saying is trust what he has to say.

Now back on track. I have a really good friend that used to work with both 6.6 and I down in the Dallas area. I can contact him and see how his work load is right now at his dealership. He used to like to do side jobs here in AZ, if I call this in to him he will probably work on the cheap. He likes Coors light and hookers.
 
B.A.Ram said:
Hmmm-so take it to gm dealership and have them put a tech 2 on it? I can just picture the mouth breather telling me its my flux capacitor right now....
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I needs a compressor. If you are making it run manually and that's the pressures you are getting then that's a definite failure...
 
6.6leater, I'm sure you mean well, but its a bad idea to tell someone without the ability to address this on their own to hot wire the compressor and check the lines.

I was careful to ask if it had been done, not to direct to do so.

From my Not-So-Smart phone
 
smokinVE said:
Well I don't exactly do the whole mouth breathing thing......

Reading threw all the posts, with your findings and what has been suggested it sounds low on charge or the compressor/clutch has given up. You not seeing any sort of sign of a leak does not mean it will not be low on charge. I think the rule of thumb is 10% loss of charge in a year. 2005 truck should take 1.6 maybe 1.8 pounds? 8-10% over the past 8 years.

The 6.6lEater+ guy you have been kind kicking around has just as many certifications as I and has been working in the stalls next to me for the past 11 years. I would not count anything he has to say out. I would put him up against any driveabillity, electrical, auto transmission tech in Merica and would win. I'm the smash and grab heavy line guy in our dealership. Guess what I'm saying is trust what he has to say.

Now back on track. I have a really good friend that used to work with both 6.6 and I down in the Dallas area. I can contact him and see how his work load is right now at his dealership. He used to like to do side jobs here in AZ, if I call this in to him he will probably work on the cheap. He likes Coors light and hookers.
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How many cases can he drink....
 
I'm sure he will make the decision weather or not he feels qualified enough to tackle this. If there is any doubt or uncomfortable feeling then stop and take it to someone. I thought I remember reading earlier that he had messed with hvac but had been awhile since.
 
6.6lEater said:
I'm sure he will make the decision weather or not he feels qualified enough to tackle this. If there is any doubt or uncomfortable feeling then stop and take it to someone. I thought I remember reading earlier that he had messed with hvac but had been awhile since.
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Lets clarify things - I do hoodrat stuff like finance and accounting - mechanical things elude me; for the most part....I'm reliant on feedback like this otherwise I'd just sit out in the driveway and lick tires....All the diagnostic stuff so far has been done by my bud Dan the diesel man.
 
He drinks a fair amount.

Lets get Dan the Diesel Man on here and see if maybe he can give us some more information that either you're not understanding or he is not telling you.
 
B.A.Ram said:
How many cases can he drink....
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If you have to ask that, the hooker may end up being the cheaper way out. :hehe:

I have no advice on the A/C other than to take it to a professional.
 
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