A/C Gurus ?

[NITROUS]

I'm ASE certified (Which doesn't really mean anything) and have been working on A/C systems for years without too many problems. Here's a good one for you guys though. I installed a new compressor, drier, evaporator, condensor, orifice tube, hoses, heater core, blower motor and controls in my 97. I've been driving for the last 3 years without a problem but decided to change things out because the blower wasn't blowing enough air across the evap since it was plugged. I charged the A/C system and it blows great and cools to 42 degrees which is great! My dilema is that when I first start the engine I can watch my discharge pressure hit 400 plus psi for a second, drop and come back up to 400 plus, drop and then level out at 225 psi within a matter of seconds but I get a P1539 high voltage code like I should. LOL The suction pressure stays close to 35 psi which I'm ok with and now that the pressures level out I'm doing good with cooling. Both electric fans are on and temperature drops. I take off down the road freezing my nut's off like I should and all of the sudden I get a P1546 Low voltage code. I run the gauges under the hood and prop them up where I can see what's going on and I see the dreaded 150 psi which drops the voltage to the pcm to 1 or less coding the P1546. Everything is new, I changed the orifice out again just to make sure there wasn't a little trash or debris on it and blew through the system again and everything looks good. I recharge, start the truck and have the same problem only at startup and only when driving. I know a little more freon will take care of the pressure issue on the road but the pressure is going to hit the pop off valve on the back of the compressor when I first start the vehicle. I've seen similar issues like this where it's been the compressor so I went ahead and got another new one under warranty. Oh, I have 8 ounces of oil in the system so I can't see that being a problem either. This sucks because it's my truck!! LOL I'm ok as long as I have a computer/scanner with me to reset the A/C code so the clutch will engage. Anyone seen or had an issue like this? Nothing has changed except for everything being new.

[RedHeartbeat]

I'm not a guru but it sounds like a bad compressor to me.

[NITROUS]

At least someone agrees with me, I picked up 2 compressors last night.

[Madd Maxx]

I wouldn't rule out a restriction - possibly in the condensor.

[NITROUS]

It's a brand new condensor, you can blow through it with no issues and the pressure settles out after a couple of seconds. With the engine off the pressure equalizes suction and discharge. I'm going to pull the orifice and replace it when I change the compressor but if the condensor was plugged I don't think the pressure would equalize as fast as it does with the engine off. I will check it again.

[GasGuzzler]

The orifice on this truck is in the line near the condenser whereas a utility has the orifice in the line near the evaporator. The part number is different (internal restriction is different). Let's make sure you have the truck part and not the utility part.

Do ya love pulling the grille?

The high side going weirdo on start up is as much a problem as it going low during driving conditions IMO.

400 is way high and sounds like low airflow or a compressor valve. I don't think it will blow off until around 460-480...?

A restriction is possible too on the high side but it would spike and stay high, right? I've had condenser restrictions that would show in operation yet blow/flow fine with compressed shop air so the previous poster has a point.

But if the low side settles quickly and stays it seems like a bad compressor as stated above.

Wish I had a set of mobile R-143a gauges like you.

8 oz. may be too much unless you know that's all there is in there. That's a lot to ever add at once.

If there is a problem with the compressor, it's a high side sucking liquid problem which was very common on the 2003 6.0 especially. Yet they raise holy hell at 3K+ RPM revved in N.

Good luck.

[NITROUS]

I love pulling the grille! I put a cat eye grille on and it takes about 45 seconds to pull off.

I'll verify the orifice but it's the single o-ring black plastic bottom and white on top that I ran before.

I won't rule out a restriction but the whole A/C sytem is completely new and was dry. I added the 8 oz. oil while dry.

I'm thinking compressor will fix the problem but I'll take everyone's advice into concideration to make sure I find the problem.

It's great to hear input from everyone because you never know what someone else has come across.

Thanks Guys!

[outlaw_king]

have you had a chance to do a compressor change yet? did that fix your problem?

[NITROUS]

I changed it last night and replaced the orifice again. No more high pressure issues but still have the low pressure problem. When I put the blower switch on low and cruise down the highway it cut's the clutch off on low pressure and throws a code. I'm going to look at adding a little more freon but I was a reading 38 degrees in the cab. I've already put 4 cans of freon in and the pressures were good last night but it will reduce cooling effiency with too much freon. This ahs to be the strangest A/C issue I've run across! I'll post what I find out.

[GasGuzzler]

I think more gas will help. Cans are 12 oz and not a pound, right? Plus the older systems take a lot more gas than the newer ones. If there are no high pressure issues this time of year but the low side is dipping, it won't hurt to slip in some more gas.