new to this forum. I usually figure things out myself, but need help now. my air conditioning is not working on my 06 2500 diesel. the problem started a month ago when the compressor kept cycling on and off for about 5 minutes after turning it on than it would work properly. now the clutch engages 6 times then completely stops. I ran 12 volts directly from the battery to the compressor and it ran perfectly. refrigerant pressures were great. I tested the voltage to the compressor prior to operating during and after it trips. it has 14 v at start up, engages 6 times then does not engage again. at this time it is only reading 11 volts at the compressor. not sure what the problem is. help is greatly appreciated.

 

If you are reading 14v+ at the battery or alt terminal with the truck running but only 11v at the compressor connector, make sure you are using the same ground when testing both voltage sources.

If that's good and still 11v, then you need to trace the wire or get a copy of the Srvc Man and use the electrical schematics to go through and test the circuit

 

I have 14 at the compressor, then the clutch engages and disengages 6 times and stops. Then I read the voltage again and now it reads 11. If I reset the a/c at the control panel in the cab (turn it off then back on) it will repeat the same scenario. 14 volts, engaged/disengage 6 times, stops and now reads 11 v. Apparently 11v is not enough to start the compressor. Not sure what can possibly cause this to occur. Was gonna replace the low pressure transducer but I don't wanna just waste money. The low side pressure is going 75 down to 70 up to 75 and down to 70 while this is occurring.

 

Ok. So jump voltage from the battery directly to the compressor. If there still does the problem, then I just know your compressor is bad

 

Already did that and the compressor runs great. Pressures are perfect, 42 deg air. Just not sure what is causing the loss of voltage and then the stoppage or clutch engagement. Should there be any stoppage of clutch engagements or should it keep trying? Should the system lock out like that or not? Can the low pressure switch be defective and cause this or can the control module be bad?????

 

Bad relay?

 

I was told there are no relays that can be changed. Supposeably it is all in the control module. I looked for a relay panel anyway and there is not one. Wasn't sure if anyone on here may have had this issue and could point me in the right direction.

 

If when jumping a good known 12 power source and it works as it should, download a free copy of the Srvc Man (see the links in my signature) and use the electrical schematics section to further troubleshoot

 

Will do. Thanks

 

you should not be anywhere around 70psi on the low side once the system is running. 35-40psi is the norm on the low side. You might need to recheck the charge on the system or it might be possible you have a blockage in the system. If i remember right, you should always have 12v on the compressor and it is grounded through the transducer. Also check the resistance in the compressor coil, i forget what the ohms should be but i have it posted on another forum somewhere. If the compressor draws too many amps, the ECM wont let it stay engaged.