New compressor, shuts off on high head pressure

[1999Suburban]

Roger that.

If I leave the OT in the condenser, than both front and rear evaps will be controlled that OT. That may work for the front evap, but not for the rear, as there's a TXV before the rear evap and having them both control flow, I don't think would work correctly. I removed the condenser OT and reassembled the system, leaving the factory OT and TXV in place. I'm going to evacuate the system again, charge it, and see what happens unless GM Tech or someone else suggests there's still a restriction somewhere I should look for.

Thank you again for your help; your site and this forum will be getting recommendations from me going forward.

[Tim]

Front Evap has the OT.

Rear Evap the expansion valve.

[1999Suburban]

Yes, that's correct

[GM Tech]

Yes, head pressure is high with two OTs in system-- go with factory method of using the OT in the condenser outlet only if it is a front only system! Aftermarket only wants to build one condenser for all Utility vehicles and let the mechanic figure out if it needs an OT or not. I've seen new condensers without an OT in them and those installed on dual systems- and they don't cool at all-- so you have to know how your system works to be sure to do it right.

Only ever use one OT in any given system!

Dual system-- OT goes in OT connection on liquid line just beyond the "Y" split to rear.
Single system-- OT goes in condenser outlet.

[Tim]

Yes, head pressure is high with two OTs in system-- go with factory method of using the OT in the condenser outlet only if it is a front only system! Aftermarket only wants to build one condenser for all Utility vehicles and let the mechanic figure out if it needs an OT or not. I've seen new condensers without an OT in them and those installed on dual systems- and they don't cool at all-- so you have to know how your system works to be sure to do it right.

Only ever use one OT in any given system!

Dual system-- OT goes in OT connection on liquid line just beyond the "Y" split to rear.
Single system-- OT goes in condenser outlet.

It is coming to my attention I'm getting old and need some Ginkoba. I remember this issue a few times when we operated the shop.

[1999Suburban]

Thank you for the lead to the cause of my high head pressure and for the assurance I need only one OT.

Waiting now for the vacuum pump so I can try again. I'll report back the results.

Many thanks, everyone.

[tbirdtbird]

Yes, please report back
Thank you

[1999Suburban]

Found the condenser had an 'extra' OT in it. Removed it and finally pulled the system into a vacuum last night and charged it. It is now working well, front and rear.

In retrospect, I have no idea why the front worked at all after the first charge and I wonder if the rear TXV that we drilled out to accept the tube was actually good. But it's cooling good now and for that, I'm a happy camper.

Thank you to everyone for your input and guidance, especially GM Tech; you revealed the culprit and saved me a migraine, lol!!

Peace,
Mike

[tony1963]

I will tell you that if you have any trash in the system, you must disconnect all of the components, remove the orifice tube and expansion valve, and flush everything (except the drier which you replace) until it runs clear. The newer style condenser must be replaced as they cannot be adequately flushed.

Any debris in any part of the system will end up right against the orifice tube as the refrigerant flows in a circuit.

[1999Suburban]

Thank you. I already did that and I'm confident it's thoroughly clean. However, if I'm wrong, time will tell.