Spooler

O.K. Here ya go. More INFO. Just fired up the truck again and the pressures came back down to normal. 28 PSI Low side, and 250 High side. I can tell you for sure we have an intermittent problem that most can't solve. The only thing I can think of is we have something that is restricting at the orifice tube or a compressor issue causing it to pump to much pressure. Now which one is it? Beemo, can you please help otherwise I will take my truck to the dealer and the battle is on. One new compressor, dryer, and Highside line with orifice. Should fix it up. If it is only one part just let us know so we don't waste any money on warranty work. Truck prices are high enough.

J BODY

...condensor temperature comes to mind. Fan clutch duty cycle the same when the reading taken?

Spooler

Noop, I checked that, Fan clutch was not on either time. I beat we have a bad compressor. Vein getting stuck causing it to jack the pressure up. Hopefully Beemo will chime in and save us all alot of headaches. The Dealership I use is a good bunch of guys. They had a truck in last week with this issue. I will be making a trip there first thing in the morning to inform them on what to look for. Tech was wanting answers himself.

MikeyB

Spooler,
When you took the reading did you have a big fan blowing air across the condenser?
You're on the right track, very high pressure on the high pressure side could be caused by a bad fan clutch, compressor, clogged orifice tube or air in the system.

MikeyB

Spooler

You are correct in your statement, but the key to my test was I was using a cold truck. I had no heat from the engine to worry about. But yes, the Condensor is clean. I keep it washed just so I don't have any issues. After thinking about it last night the compressor has to regulate it's pressure. In other words if the truck is running 2500 RPM or 700 RPM it should put out the same pressure. If the regulator gets stuck then the compressor would put out max pressure or no pressure. I just wonder if it ate itself (shelded out) pumping little pieces of metal through the system. If it did, you would have to replace the line with the orifice, replace the filter(dryer) and flush the system before installing a new compressor or it may eat itself again. Just thinking out loud. This would also explain the blast of hot air when accelerating off idle.

Spooler

Beemo, can you help us?

beem0

Hi - To get back to some of the comments....

I'll look to see how the new AC line is structured in service. The pre-06MY is 0.062 and then 06MY to 06.5MY is 0.057 and then 0.067 starting around April of this year.

I don't know a whole lot about the compressor, but its a fixed displacement so no regulation. I don't know why you would spike up to 450psi. I do know the compressor has a high pressure relieve valve that blows somewhere up in this range. I wonder if people are seeing this and the refriegerant is escaping?

Another thing to check is watch the low side when you rev the engine, I've seen where it almost pulls a vaccum which is bad.

The fan clutch is electronically controled and will kick on with high head pressure (at least the new system). Basically when you come to a stop the pressure builds and the fan bumps up, this brings the pressure down and also the panel temps. I'm not sure how to tell if the fan is working......but could be related to all this mess.

Spooler

I can check on the vaccum on the low side. I have an intermittent blockage it seems. To check if the fan clutch was ingauged I just reved the motor. No loud fan grawl so know it was not on. So if the compressor is not regulated that only leaves the orifice tube. A problem with the design, or a contaminated system (trash moving around causing a blockage). By the way on the first test when I saw 450 PSI on Highside I was getting the hot vents on the passenger side and cold vents on the drivers side. After I cut off the truck I watched the pressures to see how fast they equilzed(low and high side pressure). That was fine. After 10 minutes started truck again. Pressure in my mind were perfect 28 PSI Low and 250 PSI High. All the work I have done it the past I would classify this as perfect. I checked the vents on passenger side and drivers side. Very small difference but cold. If you can't give us any insight the only thing to do is first, replace the highside line with orifice tube. If that dosen't correct it then replace the compressor.

Spooler

If the pressure relief valve pops it normally loses all refrigerant. I have diagnosed this before on another model. Had to replace the line with the relief valve.

Spooler

Beemo, I hope you have some pull with D.C. I would hate it if we know what is wrong and can't get anyone to correct the issue. I can't afford a new truck and really I just don't want one. (My truck is new only 32,000 miles) I am happy with the one I have except this darn A/C problem.

Hounddog

I basicly won't drive mine in this heat.I use my 1500 because of this ac issue.

beem0

I don't know the magic fix......

I'm driving a 04.5 diesel today in this hot weather in Detroit and the thing is fine. When in fresh (not recirc) the vents warm up when you come to a stop because of the lack of condenser airflow, but then come back when the fan comes on. I actually had to turn down the blower from being cold!

The liquid line where the orifice tube is located is cheap and easy to replace, but you will obvoiusly have to reclaim and recharge which is not cheap. If you go with the 0.067 FOT size the idle performance will not be as good (maybe a couple of degrees higher) but the left to right split will be better.

This high pressure concerns me.....no wonder the vents are blowing warm!

Also, the relief valve is on the compressor (I suspect since it is on the 06's). You can usually tell if it went off as there is oil all around it. Which reminds me....add oil when you recharge!

Spooler

It could be that some trucks are worse then others. You guys need to get a good test truck. You aren't going to fix it if you can't see it. I just got lucky last night, but sometimes it is better to be lucky than good. I don't drive my truck everyday thank goodness. I will try and make the high pressure spike again tonight. I am taking my truck into the dealer next week. Some support from STAR for the tech would be great. (Approve some part swapping, my truck is still under warranty) That way if we can find the issue you will be able to lay your hands on the bad part so you can see what happend to it. I don't know how this will turn out, I hope very well for everyone's sake that's sweaten in the heat.

Oh yeah, When I did my test I had the vent on MAX (recirculate), blower on level 4, and driver's side window down. I have always tested this way. So I don't think it is the low air flow causing the vent temps to be very different. It is no doubt the pressure spike on the High side to 450PSI. Actually It stayed their until I turned the A/C off.

MikeyB

From the lastest info here maybe DC should install a electric pusher fan on the front of the condenser? Sure would help the A/C during idling conditions.

MikeyB

Spooler

I looked at my truck today. I see no room at all to be able to install a fan. I have a few laying around from another vehicle I tried this on. Mechanical fan clutch was much better for cooling. Being that ours are electrically control it should not be too much of an issue to reprogram the ECU(reflash) to optimize it.