2000 Winnebago front heat/AC problem

In Mr. Bishop's diagram, the Vacuum Check Valve would either be part of the Reservoir OR beyond the "To Source" arrow. It appears the Temperature Control Door works off Vacuum, but modulates by the control device in the lower left of the diagram. On our Ford, temperature control door is modulated by an electric servo motor.
I was able to find a couple wiring diagrams for SCS/Frigette, but they don't show the whole control system. It's a .PDF file so I don't know if I can post it, but I can email it if requested. Just send me a PM. The diagrams imply to me that the system controls temperature with electric valves. If so, that arrangement differs from both Ford and Evans.

I would add that evanstempcon.com(link) will give you a lot of info on RV dash system. Some Winnies use Evans, mine does.

wrrn73 wrote:
Ok thanks. I was thinking a vacuum problem but just didn't know where to look.

You can look here to view an example of how the system works.

Google for images of the reservoirs, then look under the doghouse, infront of the fire wall and find yours. Connect your vacuum gauge to the dash side of the reservoir start the engine and make sure that the vacuum holds when you turn the engine off. Then find and check each individual line using the gauge. When you find one that won't hold a vacuum you have found your leak.

Mityvac is a great tool and available from almost any auto parts store. HFT carries their own brand but I don't know how good it is. The Mityvac at HFT is $43 and their store brand is $25.

There's a ton of trouble shooting info, read, check, read...

Ok thanks. I was thinking a vacuum problem but just didn't know where to look.

This is brought to you courtesy of my droid phone sitting on the roof of the coach in hotspot mode. No internet inside...

I did two threads on the problem we had with the E450 in signature. The BATAuto Thread has a little more detail than the RV.net Threadbut a lot of the information and photos appear in both.

Class A's can be difficult. Do you have any paperwork indicating that your HVAC actually IS a Ford system? I looked at the F53 pages on Ford's website awhile ago and I think the HVAC was provided for, but not installed. There's a good chance your system is not Ford and...

... I suspect it might not be, since you said you cannot regulate Temperature. On a Ford system, an ELECTRIC (not Vacuum) servo controls temperature by moving a "Blend Door." At least the BAT thread shows a diagram with Blend Door. In that system, A/C and Heat are both Full ON Full Time. The Dashboard Control Knob controls the servo electrically to move that Door, Blending Hot and Cold to provide the comfort you called for.

Common Class A HVAC systems were SCS Fridgette (now out of business) and Evans Tempcon (still active). Auto HVAC used to use Vacuum to control Water Flow and therefore Temperature. Learning this could help figure out what we're working on.

They're in default mode due to a vacuum failure. On E-SERIES, F-SERIES Pickup and many other Fords the vacuum tank is inside the HVAC cabinet and the fix is to bypass with new check valve, tank, and hose. Or a mouse could have chewed a tube. Anysign of rodents? You might be able to trace. On ours source from engine is red and feed all the way to control is black. More later when I can get better internet and use my PC.