Ideas on why my Air conditioning in my truck doesn't work

[phughes69]

Last year I hit a deer and it wiped out my front end. Insurance paid for it. After I got the truck back (1996 c3500 chevy dually) the AC didn't seem to blow as cold. I took it back to the collision shop that fixed it. They leak checked it but could not find any leaks, and tried refilling it. They put in about 1/2 lb of r134a. It still doesn't blow cold. What would affect the AC system in a deer collision that would cause the air to not blow as cold. I checked the compressor and it is engaging. Any thoughts? This is stumping me and wanted to see if anyone else had an experience like this.

Thanks
Pat

[DmaxMaverick]

Several possibilities.

Overcharged (now). Too much R134a will cause your condition.

The impact could have dislodged debris in the system, blocking the orifice.

Damaged condensor. It could be damaged somewhere that can't be seen.

Being that, other than the grill, the A/C condensor it the forward most stopper to anything that hits the front of the truck. I certainly would blaim the collision for it not working properly. Take it back to the shop to get it corrected. Insist they get it right. It was working before the collision, right? They got paid to correct it.

[Peter J. Bierman]

If one off the condenser pipes is bent or ever pushed flat, you now have a restriction like the regular orifice but way to early.
If so the line to the evaporator must be cold.
if it is realy blocked it must be visible on the gauge set and the compressor will disengage on high pressure.
Those aluminum pipes are often hard to see but at the evap easy to feel.
The line should be warm at like a foot before the evaporator.( this is the thinner line )

Peter

[HowieE]

The above comments are all correct. But rather than look for a problem at home go back to the shop and have them put a set of guages on the system and show you what they read. There are set standards for the system under any operating conditions. If the system is not within these standards a good AC man will be able to tell you what is wrong. The collision shop may not be the place to fix it but they should be the ones to make sure it is fixed since they took them money.

[phughes69]

Thanks for all the replies. The vent door and temp control door are controlled my small stepper motors. I pulled apart the dash to make sure the temp control door was opening and closing all the way and it was. I then got all the factory specs on what the hi and lo side pressures should be. I went back to the Collision shop and had them recover the refrigerant, vacuum it down and recharge it. When the AC system was running the the hi and lo side pressure were 145 and 75 respectfully. They should have been 320 and 28. (all in PSI). So I think the compressor is shot. No I have to fight with the insurance company to get them to replace the compressor (about $250.00). Does my hypothisis about a bad compressor sound right?

[phughes69]

Thanks for all the replies. The vent door and temp control door are controlled my small stepper motors. I pulled apart the dash to make sure the temp control door was opening and closing all the way and it was. I then got all the factory specs on what the hi and lo side pressures should be. I went back to the Collision shop and had them recover the refrigerant, vacuum it down and recharge it. When the AC system was running the the hi and lo side pressure were 145 and 75 respectfully. They should have been 320 and 28. (all in PSI). So I think the compressor is shot. No I have to fight with the insurance company to get them to replace the compressor (about $250.00). Does my hypothisis about a bad compressor sound right?

[HowieE]

If the pressures were taken after a measure charge was put in, not just reading they took when you showed up at the shop, the low head pressure and high suction pressure sounds like a valve in the compressor. Try this. Start the system and have someone hold the rpms at about 1800. After about 1/2 min of this running touch the suction line, the larger one, just short of the compressor. If the suction line is warn at this point and reduces in temperature as you work you way away from the compressor it is most likely a bad valve. If it is a valve it is unlikely the deer had anything to do with it.

[phughes69]

I was there where we he refilled the system. I actually had to tell him the proper way of doing it. When I worked for GM we recovered and charged AC systems a lot. So the pressures I saw are accurate. When the AC system is on and running for a few minutes the hi side is really warm about 2 inches away from the compressor and the lo side is only cool. The lo side line is about the same temp all the way from the compressor to the receiver/drier, just cool. Plus there is NO condensation on the receiver/drier when I had it running for about 10 minutes.

[phughes69]

HowieE , What valve are your refering to? The actually compressor or something else.

[HowieE]

In the compressor there are several vain type chech valves to prevent high pressure gas from getting back into the suction side. When one fails it causes blow back into the suction line right at the compressor manifold and thus the line is warm but should get cooler as you go alone the line towards the receaver.
With the pressure you are seeing and no evidance of warmth on the suction line it may be one of the valve on the high side not seating.

[TAG]

It sounds like the body shop where you got your truck fixed failed to put an orifice tube in the new condensor which i assume they replaced, it goes in the outlet of the condensor on GM trucks. that situation would cause the pressures you got on the guages, if you havn't already fixed the problem its worth a look.

[charliepeterson]

I've done a few A/C jobs in the last ten years and the pressures I'm looking for are 150-170 and 20-30. A weighed charge will be right on the money. The Suction line should sweat from the Accumulator to the compressor as long as the humidity level is high enough. A nice cold line is good too.