07 M1165 Crew Heat Issue

[Rooster915]

Good Evening all,

Relatively new to the forum but have a few questions. On my M1165, the AC blows cold and works as it should, but when I switch it to heat the blower motor cuts off and i get no air out of the vents. It does the electronic heater valve deleted with a manual one in it's place. Which I've ensured is open. I've been looking at the TM schematics and tracing wires with no luck.

Does the electronic valve have to be there for the heat/blower motor to work in heat mode?
I'm not sure if the heater core is clogged yet as I've been stuck trying to get the blower motor to blow in heat mode, which it does not.

Any advice or guidance where to go next on troubleshooting would be greatly appreciated.

Thank you to anyone who helps in advance.

 

[DREDnot]

No, the water valve being unplugged wont affect the fan.
My first thought is that your jumper diode may be geeking? Check out the wiring under the instrument cluster for proper hookup

 

[Dieselmeister]

Since you have a manual valve, disconnect one of the wires at the compressor, and run it in the AC mode (compressor off), and check if the heater works and blows hot air. If the heater works, then the next step is to go over the wiring with a voltmeter or test lamp, to see why you are not getting power to the fan in heat mode.

 

[Rooster915]

No, the water valve being unplugged wont affect the fan.
My first thought is that your jumper diode may be geeking? Check out the wiring under the instrument cluster for proper hookup

View attachment 958726

Everything is wired correctly. Is there specs to test the resistor? I'm considering just ordering a new one to see.

 

[Rooster915]

Since you have a manual valve, disconnect one of the wires at the compressor, and run it in the AC mode (compressor off), and check if the heater works and blows hot air. If the heater works, then the next step is to go over the wiring with a voltmeter or test lamp, to see why you are not getting power to the fan in heat mode.

It does blow hot in AC mode with the compressor disconnected.

 

[DREDnot]

Does the fan blow high and low speed in AC mode? And when you turn off the AC switch the fan shuts off completely? no high or low?

And are we talking about the front unit fan by the commanders feet? Or the rear AC unit?

 

[Dieselmeister]

It does blow hot in AC mode with the compressor disconnected.

OK, your fan is getting power via the AC switch, in AC mode, but not from the control box, when the AC is off. Check wire 27 / 27D (on the diagram) going to the center of your fan switch. That should have 24 volts on it. if not, follow that wire to see where the power is getting lost.

 

[Rooster915]

Does the fan blow high and low speed in AC mode? And when you turn off the AC switch the fan shuts off completely? no high or low?

And are we talking about the front unit fan by the commanders feet? Or the rear AC unit?View attachment 958797

View attachment 958798

We are talking the front unit by the commanders feet. If I turn AC off the fans stop completely. No high or low heat. Attached is a photo of the position in which hest doesn't work.

 

[Rooster915]

OK, your fan is getting power via the AC switch, in AC mode, but not from the control box, when the AC is off. Check wire 27 / 27D (on the diagram) going to the center of your fan switch. That should have 24 volts on it. if not, follow that wire to see where the power is getting lost.

Got it when I get off work in a few ill grab the multimeter and check that.

 

[Retiredwarhorses]

Make sure the switch’s aren’t installed backwards, I’ve had them come in where the AC switch is on the Heater location and Fan switch is on the AC side….

 

[Rooster915]

Wanna give a huge thanks to yall. It was a bad diode thing. Replaced with new and wired it correctly (definitely was off before) and no heat and ac works properly