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Air Conditioning wiring help

Posted

I'm following the ac wiring diagram on this website:

Key in the on position.

 

With the ac selector switch in the "face only" position and the blend door on all the way blue I have power at the LTGRN/WT wire at the PCM. This indicates to the PCM I want AC and there is not high pressure condition.

 

When I tested the brown wire beside the LTGRN/WT there was no power coming from the low pressure switch, meaning again that there is no reason the compressor shouldnt start.

 

I tested the DRKBL/ORG wire that is leaving the PCM. When I'm first putting the probe on the wire it flashes green but then goes away when I make solid contact on the wire.

 

Does this lack of power leaving the PCM mean that internally the PCM is damaged or does it mean that there's a ground in the wire?

 

Currently I have the ac relay removed and a switch rigged to tell the compressor when to turn on and off manually. This works but is annoying and want it fixed correctly. If the PCM is the problem then I'll probably just make a switch directly from the LTGRN/WHT to the DRKBLUE/ORG and set to ground the wire when the low pressure switch is activated.

 

Edited by Ng321
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Double check your logic theory.

 

Go get the PCM to command the Clutch coil to pull in it will need 2 things.  The command from the heater control on the light green/ white.   AND

 

It will also need a 12v input coming into the PCM on the brown wire confirming that the high pressure AND low pressure switches are closed. 

 

  On 6/22/2020 at 6:34 PM, Ng321 said:

When I tested the brown wire beside the LTGRN/WT there was no power coming from the low pressure switch, meaning again that there is no reason the compressor shouldnt start.

 

 

I think that is your problem.  Put the system back together and just put jumpers in both the high and low pressure switches.   If it works, one of the switches are bad.  I am pretty sure both switches are hot swappable. 

 

HTH

 

Hag

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Thanks for the reply.

 

With the key off there is power on the brown wire, with the key in on it there is no power.

 

Even with the compressor running with a bypass power supply the brown wire has no power.

 

This makes me believe that you're correct Haggar and it low pressure switch is the culprit.

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Welcome To Mopar1973Man.Com LLC

We are privately owned, with access to a professional Diesel Mechanic, who can provide additional support for Dodge Ram Cummins Diesel vehicles. Many detailed information is FREE and available to read. However, in order to interact directly with our Diesel Mechanic, Michael, by phone, via zoom, or as the web-based option, Subscription Plans are offered that will enable these and other features.  Go to the Subscription Page and Select a desired plan. At any time you wish to cancel the Subscription, click Subscription Page, select the 'Cancel' button, and it will be canceled. For your convenience, all subscriptions are on auto-renewal.