Running the no idle AC while the engine is on?

There is usually a trigger wire going to the APU computer. It is hooked up to recognize if the ignition is on or off. By disconnecting it, you will be able to run this.

 

Are you talking about an apu or what. My trucks are older, but every truck I have ever owned, the bunk air ran off the same compressor as the cab air.

 

I wouldn't wish a Navistar product on my worst enemy. Focus on the voltage drop off of pin 22 on the ECU 36 pin connector (AKA, Pin 4 on the main 30 pin connector) with the engine running. It's usually a yellow or green to grey and everything is labelled. Turn the engine off and you should notice a slight voltage change on that pin. You probably won't see a normal drop like other manufacturers with an ignition alarm from B+ to 0V. This is because Navistar is one of the only companies to turn an awesome Bergstrom HVAC system into a science project... Do I sound bitter? Cut that wire IN THE MIDDLE with enough room to repair and see if the system works with the engine running. You might have to install a 4-pin relay with an ignition trigger if you have an older system.

This is my first and probably only post on this website. Take care

 

Does anyone want to tell him what that shielded yellow (and green) wire is?? Lets see who has been paying attention over the years...

 

It's a DLB based system. Your average trucker won't have a Nexiq or the software to program it properly. Just trying to help people out.

 

Also, you only need a relay if you want to control the AUX system via the dash. It goes without saying, but sending 12v through the twisted pair will damage the ECU... and don't use a Power Probe.