Like the title says my A/C will run great for a couple min. Then the compressor will disengage. It won't even engage if I stick a paper clip in the pressure sensor. But when I hook it up to efilive and manually control the ac relay it works fine. Would this be a faulty relay?
LB7: A/C not engaging but will with efilive
- Thread starter bmemmott
- Start date
this would mean you need to hook a set of gauges up to the system and give us readings. DO NOT try to bypass the issue. you could inadvertently kill the compressor or blow a hose. We need really gauge readings as well, not jsut the cheapy cold side gauge you can get at just about any auto store
those pressures are way low. has the system been opened up prior? sounds like you got a leak starting
It has not been opened since I got it 6 months ago. What should the pressures be? I can start tracking down a leak.
no fan on at 2k rpm, a/c full blast in 90*+ ambient temp i see pressures run well above 300psi on the high side till the fan kicks on. Low side should be right around 50psi. with everything off (including the vehicle), you should see pressures level off to 120 or so psi.
im assuming the readings you gave are when the compressor would be on correct?
im assuming the readings you gave are when the compressor would be on correct?
either one could be. i dont know the specs on the low or high side sensor and what pressures they cut compressor power but 9/10 times they are not bad.
Double check and make sure that the O/S of the tune is for a 03-04 truck, if i is for a 01-02 it could be causing the issue.
GMC_2002_Dmax
The Still Master
Latest update... I went back to the stock tune with no change. Then I tried the controller out of a different truck, no change.
Now I scan the DTCs with V2 and I get HVAC ?DSW B0159 with no description and DSW U1000 Class 2 Data Link.
Now I scan the DTCs with V2 and I get HVAC ?DSW B0159 with no description and DSW U1000 Class 2 Data Link.
Those pressures are dead on for a 70 degree ambient temp. If it was 90 out you should see about 50 low and 225 high, but for 70 your pretty close. And if it comes on when you command it via EFILIVE then that means the low pressure switch is working as well as the high pressure switch. The ECM will not command the A/C with the engine running if either switch is open. Sounds like your not getting an A/C command from the control head. Is it manual or auto climate control?
Thank you. I just figured it out! The ambient temp sensor was bad. Swapped it with one from another truck and the compressor kicked on.
Thanks for the help everyone!!
That's definitely not common but I've seen it. Glad you got it fixed!!
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