Dash Heating and A/C Controls Not working

[DalePal]

I have a 2008 American Heritage. My first trip out, I am 3 days in and the heater/AC Fan Controls are not responding to inputs. They were working fine, and then just stopped. I have checked all the fuses I could fine, under the steps, in the bays etc... none of them were blown. The fan knob clicks as I move it from low to high, like normal. The heater/cool adjustment knob turns like it should, but since there is no air moving, not sure if it is doing anything.

Thanks for any advise/direction.

[KCFDCapt]

Do you hear the blower running? If you hear the blower but no air moves, I would check for a vacuum line problem. The vents are controlled by vacuum operated louvers. Without vacuum - no air movement.

[153stars]

Usually if you lose blower resistor pack you still have high. If loss of controls for dampers ,default is to defrost for safety. Have you actually located "the" blower fuse. Not unheard of to a lose blower motor but they tend to lock up and squeal a bit first , "not a rule though".Most heater controls are adopted from auto/truck parts. I suppose the fan dial could fail, it would be my last bet. Always suspect grounds.

[Ray,IN]

Firs things first. Have you determined if 12V is present at the the control panel?

[Rob_M]

Originally Posted by KCFDCapt

Do you hear the blower running? If you hear the blower but no air moves, I would check for a vacuum line problem. The vents are controlled by vacuum operated louvers. Without vacuum - no air movement.

Diesel pushers do not have vacuum.

[Jon_C]

Originally Posted by Rob_M

Diesel pushers do not have vacuum.

Some like mine have a small vacuum pump for the a/c controls up front.

[RealNiceTent]

Originally Posted by Rob_M
Diesel pushers do not have vacuum.

Originally Posted by Jon_C

Some like mine have a small vacuum pump for the a/c controls up front.

There are a lot of diesel vehicles including medium duty trucks, cars, motor-homes, and step vans that use electric or engine driven vacuum pumps to supply vacuum for brake boosters, emission control systems, climate control and accessories. Cummins "B" engines are frequently fitted with a vacuum pump run off the drive on the back of the timing case. Newer vehicles are less dependent on vacuum for control systems. Digital stepping motors have pretty much taken over those duties.

[MrMark52]

Quite often the blower speed switch gets burned up due to the poor design of the switch and the high current the blower motors pull.

Noting you say you are not feeling any air moving tends to indicate to me that you may have this problem - we do on our ‘02 coach, and I’m in the process of replacing the switch and adding relays that will handle the motor current while the switch will only handle the relay coil current (I plan to document the process to IRV2, hopefully finishing today).

[153stars]

Can also "like mine" use a vacuum inducer. They use air pressure , just a small flow from the air compressor to make vacuum
.

Originally Posted by Jon_C

Some like mine have a small vacuum pump for the a/c controls up front.

[Rob_M]

Originally Posted by RealNiceTent

Originally Posted by Rob_M
Diesel pushers do not have vacuum.








There are a lot of diesel vehicles including medium duty trucks, cars, motor-homes, and step vans that use electric or engine driven vacuum pumps to supply vacuum for brake boosters, emission control systems, climate control and accessories. Cummins "B" engines are frequently fitted with a vacuum pump run off the drive on the back of the timing case. Newer vehicles are less dependent on vacuum for control systems. Digital stepping motors have pretty much taken over those duties.

I was aware that many diesel vehicles have vacuum pumps. Didn’t realize some DP’s did also. My American Coach on Spartan does not. (that I’m aware of). Appreciate the correction.

[DalePal]

Thanks to everyone, looks like I need to add a little more information.

First, I turn the fan knob and absolutely nothing happens, My first guess is a fuse. I looked everywhere and have not located a blown fuse. I may be missing a fuse block. I found these fuse blocks: 1. Under the stairs, 2. In the bay on the passenger side mid way down. It has a cover that you have to turn a knob in the middle and the cover comes off. There were two different fuse blocks like this. 3. In the last bay on the passenger side, alongside the motor.

The motor is a Cummins 10.8L 500HP if that helps.

I could have a burnt out switch, since it was working fine, and just stopped. I have limited access while on the road. Will be back home January 10th (about 2 weeks from now) and will have more ability to diag.

My gut tells me I am missing a fuse block, or missed the blown fuse...

[Jandcinok]

We have an 09 Tradition, the duct dampers are driven by small servo motors. In the front drivers side compartment (under the driver) is the ac lines, dryer, heater core, etc. look for an inline fuse close to the blower motor. I dont know if thats your fix, but look at it.