Air Pump for HVAC

[BFlinn181]

The schematic shows what Evans Tempcon provides, but note the vacuum pump and a fan to cool the A/C condenser coil isn't shown, but found in most all diesel RVs. In addition, unless the heater control valve is vacuum operated, it doesn't show how coolant flow to the heater core is regulated. Nothing wrong with that, but does show that there are still parts not explained. As long as you install a vacuum pump that can do the job, it doesn't need to be an exact replacement.

[zzjea]

My suspicion is that the vacuum switch may be the problem. While the HVAC was running (control switch on), I put in a 10 a fuse the other day and the pump ran and doors activated and operated properly until I switched the control knob to off and back on again. It could be the control (vacuum) switch, so I am trying to see if I can test that switch on the bench with a multimeter to see if it has anomalies.

[RKins]

Here is a diagram for a pusher. I too am trying to figure out my dash AC - I only get air out the defroster - so the vacuum is suspect - this topic came up at a perfect time.

[zzjea]

I have solved this with a workaround. The pump is good, the controls work fine, so I remounted the pump in a bay nearby where I can access it easily. I ran a new vacuum hose from the pump to the cannister and wired the pump to a fused circuit. Everything works great. Don't know why the original setup failed and I stopped trying to research it.

[Skip426]

John; thanks for wrapping up your post , glad you managed to get things working.

I'll throw in a note for Rick ( RKins ) I have to question the accuracy of the diagram; you posted; because several components shown as chassis builder supplied in the diagram ( condenser , condenser fan , receiver/dryer ) on my chassis still have Evans/Tempcon , part # tags on them.
So if you need parts and your chassis manufacturer says they don't supply them you'll have to check with Evans.