I am having an issue with the A/C in my M916.
The symptoms are the A/C works intermittently, ONLY
after shutting the truck down. Sometimes the A/C works
when I restart and sometimes it does not.
The A/C will be working fine, I shut off the truck and then restart
and the A/C "can" be dead, or it "can" be ok!
It only dies after an engine shut down.
It does not die every time!
It is a Red Dot #RD-2-4530-0 system. I believe the main evaporator
assembly in the cab to be VERY similar to many other RD
military style systems.
For the first 6 months or so after install there were no issues, none.
Then one day I climbed into the cockpit after 2 weeks of no use
and I saw the A/C switch was left on, and the A/C did not work
when I started the truck. This should not be an issue IMO.
The WHITE wire from the control panel connects to one of the two
open electrical tabs on the ignition switch. I connected a multimeter
to this tab and I get 11.55 Volts when I cycle the key to ON.
I get 0 volts when key is off. I get the same results when
the A/C is dead or when the A/C is working. IMO this rules
out a bad ignition switch. (I replaced it anyways prior)
The A/C system is wired directly to the batteries FWIW.
When the A/C dies, so does the compressor clutch.
The A/C only dies AFTER I shut the truck off. The A/C will
die regardless of the position of the A/C switch, so on
or off when I shut off the truck the A/C "can" die, but
not always! Remember it acts up intermittently !
When the A/C is working, w/ the A/C switch ON, when you cycle the
ignition switch from OFF to ON w/o pressing the start button,
you can hear the compressor clutch engage and disengage.
When the A/C is NOT working, w/ the A/C switch ON, when you cycle the
ignition switch from OFF to ON w/o pressing the start button,
you can NOT hear the compressor clutch engage and disengage.
So when things go south I seem to loose power everywhere.
The circuit breaker on the A/C unit itself, never trips...
Are there any relays in the A/C system that can be INOP?
Other things I have done;
I have removed all 8 electrical relays and tested them w/ a “Relay Buddy” to 100% good.
I have checked continuity on all Circuit breakers in the dash hole.
All circuit breaker wires are snug.
I have 2- 12V Batteries not 4 monster military batteries fwiw.
Everything else works 100% in the truck that I know of. The truck is
borderline pristine w/ 3800 miles since rebuild. Rebuild was a frame off reset.
The only wiring I have changed is I added a license plate light in the back.
I swapped in the upgraded charging system that WAS designed for the truck,
to the letter of the instructions.
I added a car radio, it gets power directly from the battery, there is an exciter
Wire from the ignition switch to the radio, it connects to the same tab as
the A/C white wire. Otherwise the wiring harness is stock and was
Replaced new in 2008 and is unadulterated.
CLICK HERE for the A/C installation manual
Anyone have any input?