Dash Air Workhorse

All you do is clamp off the Water hose that feeds the Evans valve and run your dash AC. If it always cools with the hose clamped OFF, there is no reason to pay for a 134a check out. Just replace the Evans valve. Doug

harold1946 wrote:
Workhorse used the Evans system on all P series chassis.
I would suspect the tempcon valve.

Thanks Harold, and hope out of the heat!

Workhorse used the Evans system on all P series chassis.
I would suspect the tempcon valve.

Thanks John & Ronnie I suspect that hot water valve to be the culprit?

There is a valve that is supposed to close and keep hot water out of your heater core. This valve is known to leak, as it does on many other types of vehicles. I cut my heater hose and installed a shut off valve that i use during the period of time when I am using my dash AC and have eliminated that problem. These universal shut off valves are available at almost any parts store and include a twist type manual control for you to shut off all water flow through your heater hoses.

I suspect the air is working fine it is the heater that may be the problem.

Now, I do not know if Workhorse or the body builder chooses the HEVAC system but on my Damon it is an evans.. MOST modern automotive air conditioners work like this.

They A/C runs full time, flat out, if you feel a bit.. cool.. and adjust the temp setting, well then what they do is add heat.. (I mean why not turn off the compressor and let it warm up a bit naturally.. Frankly I do not know other than that would give you better MPG and .. Well conspiracy theories abound).

The hot water flow control valve to the heater is a known "Issue" sometimes it sticks open.

Mine was warm all the time (not hot not cold) so I clamped one of the heater hoses.. NO difference.. THEN I added 12 oz of R-134A.. Big difference.. I will have a pro finish the job next scheduled service.