A/C Techs Please_Charging issue

[Mad_Trbo]

Last night I hooked up my vacuum and pulled the air conditioning system down to right around 28 in/hg. The system held this for at least an hour, at which time I decided to charge the system.

This is a brand new system with exception to the evaporator. I think that is the unit the orifice tube feeds into and the accumulator as well.

So I let the system pull in approximately 2 and a half cans of r134a at 12 ozs per can. Estimating this to be about 2.6 lbs or so. Somewhere behind the compressor, seemed to be where the bulkhead fitting bolted to the compressor I hear a hissing noise.

A couple of questions:

1st That isn't supposed to happen right.

2nd As the system was drawing in the refregerant the low side qauge read as high as 70 psi. I thought it was only supposed to be as high as 35 - 40 psi. Is that correct?

3rd If indeed I do have a problem on the back of the compressor and I resolve this. Will I need to reclaim anything I have put in the system and start over?

4th I started the car and could not get the compressor to engage, brand new compressor. I tried jumping the switch off the accumulator the fans would come on but no clutch engagement.

 

[driveshaft man]

I have had trouble with the sealing washer thickness on replacement compressors....and leaks between the case ends on rebuilt units.
If you can't make to compressor run by bypassing the cycle switch ,the compressor or clutch is bad...replace it.

 

[Mad_Trbo]

Cycle Switch.

is the cycle switch the switch on the side of the accumulator.

 

[Nick Micale]

1. "Hissing" noise could be a leak or internal?

2. 70 psi is normal when charging, when can is empty or system charged, should pull to 25-30 psi.

3. If it is a leak, you will have nothing to re-claim. :smile:

4. Check and see if you have power AND ground at the compressor.

 

[Mad_Trbo]

Good Info

All good info.

I wonder how it was able to hold vacuum with the leak.

Pump hooked to center inlet on manifold set and low pressure side open.

Just a new system to learn.

 

[driveshaft man]

is the cycle switch the switch on the side of the accumulator.

Not sure,I'll look tonight. Most GM pick-ups are--and on 2 wire plug with green wires .It will be on low pressure line somewhere .Unplug and use a pair of needlenose plyers or a short piece of wire stuffed into plug to make compressor run.Make sure 12V is on one wire...if not, ck fuses .
I have not had to work on my GNs AC......yet.
Vacuum needs to be done with both valves fully open

 

[DailyDrifter]

I wonder how it was able to hold vacuum with the leak. QUOTE]

It can happen! When you pull a vac it will hold fairly well, BUT when you put PSI into it, it will push the fitting out. I had it happen on my Nissan, it held vacuum but as soon as it was charged the pressure pushed the fitting out.

 

[Mad_Trbo]

One thing at a time

I have had trouble with the sealing washer thickness on replacement compressors....and leaks between the case ends on rebuilt units.
If you can't make to compressor run by bypassing the cycle switch ,the compressor or clutch is bad...replace it.

I put voltage and ground to the compressor and heard the clutch engage so I at least know the clutch engages.

About the sealing washers, what is the fix here? I am pretty sure it has to do with the sealing washers. I would move the two lines attached to the a/c manifold at the compressor and the pitch of the hiss would change. The lines themselves are new units. I am certain the issue is those washers for the leak.

 

[xrunner123]

Make sure that the high pressure switch on the compressor closes the circuit. If it is not connected or the pressure switch is open for some reason the compressor clutch will not engage.

And make sure that the A/C relay kicks on and completes the circuit.

 

[driveshaft man]

I put voltage and ground to the compressor and heard the clutch engage so I at least know the clutch engages.

About the sealing washers, what is the fix here? I am pretty sure it has to do with the sealing washers. I would move the two lines attached to the a/c manifold at the compressor and the pitch of the hiss would change. The lines themselves are new units. I am certain the issue is those washers for the leak.

Somebody(Four Seasons?) sells an assortment of sealing washers.Select thicknesses that will allow manifold to tighten up parallel to rear of compressor mount....and coat all surfaces with a little compressor oil.
Possible too that leak is from defective weld to join tubes to manifold....use spray bottle mix of liquid dish soap to make bubble solution to show the leak more clearly.

 

[Mad_Trbo]

3 wire plug on the back of the compressor

What is the three wire plug's purpose on the line going to the compressor.

I am trying to trace my issue down as to why the compressor is not cyling on without manual intervention.

Does this three wire plug have anything to do with the compressor. It seems t be some sort of pressur sensor.


Thanks again for th assistance.

 

[xrunner123]

What is the three wire plug's purpose on the line going to the compressor.

I am trying to trace my issue down as to why the compressor is not cyling on without manual intervention.

Does this three wire plug have anything to do with the compressor. It seems t be some sort of pressur sensor.


Thanks again for th assistance.

overpressure sensor. Turns on fan.

 

[Mad_Trbo]

A/C Cut out Relat

Still getting now power to my a/c compressor clutch.

I love my volt meter. After I was sure my charge was correct I carefully went through the electronics of the A/C system. With schematic at my side and voltmeter on my hip. I performed the following;

I made sure A/C relay was operating corrected. Checking that with power and ground the relay would close. With relay closed I checked for resistance across the power circuit everything looked good.

I then checked for resistance across the wire carrying power from the relay to the clutch - everything looked good.

I then checked the the low pressure switch which is actually responsible for carrying switched power to the relay - everything was good.

What does this leave? The EMS and the point of ground for the relay. I did nothing here simply assumed the EMS was not pulling ground. The way I understand it is the A/C cutout switch monitors for load and if it sees xxxx load it opens the switch keeping the A/C cutout relay from seeing ground. Thus not transferring power to the A/C clutch.

My questions;

What is the EMS monitoring for load - TPS - MAP Power Steering?

Would an improperly ground EMS stop the EMS from being able to ground the a/c cutout relay?

Has anyone else every experienced this issue?

For now A/C runs fine with EMS switch cut and ground run tothe chasis. I am thinking that if I can't figure this out, I am going to look for an open hobbs switch or something that can read voltage on the TPS and run my own external WOT switch to provide ground to the a/C cut out relay.

 

[BADDGUY6]

Xfi

What is the three wire plug's purpose on the line going to the compressor.

I am trying to trace my issue down as to why the compressor is not cyling on without manual intervention.

Does this three wire plug have anything to do with the compressor. It seems t be some sort of pressur sensor.


Thanks again for th assistance.

Did you check your XFI "AC Clutch Control" settings?

 

[Mad_Trbo]

Wow!!! Problem solved

Did you check your XFI "AC Clutch Control" settings?

Thanks Baddguy, that appears to be the issue.

With this build I upgraded XFI's firmware and didn't notice this in the revision upgrade. When you first mentioned this I was like what is this guy talking about.

Was this in earlier versions and just to let you know bad I was. I had version 1 of the firmware prior to this rebuild.

Anyway the short of it is, Max CTS was set at 10, no wonder!

Thanks and thanks again! I haven't made the change and re-wired, but I am going to assume based on everything else this is the issue.

 

[DailyDrifter]

Did you check your XFI "AC Clutch Control" settings?

Good catch, I didnt read his sig.