V10 2v f53 1999 No vacuum at heater switch

[Lake11969]

I have vacuum at all the lines, but the inline heater and the air door.(Green line) I check all line for leaks,and the back of the heater control switch. I have no control of the heat, On all the time. Do I need to change the switch in the dash?

[LVJ58]

The heat on our 2000 is controlled with a valve regulating the water flow into the heater core. It's a mechanical valve and activated with a steel wire cable connected to it at one end and the temp control knob on the dash on the other end.

When you open the access panel on the front of your coach, the valve will be on the curb side of the coach close to the HVAC housing. You will see the rubber heater hose attached to it.

As you rotate the Temp knob on the dash, the wire connected to the lever on the valve will either open or close the valve depending on the direction of control knob rotation.

You might check to see if the steel wire is broken or come loose from the lever on the valve.

Good luck and keep us posted on your progress...

[garym114]

It is probably an Evans Tempcon system. The link is for the various troubleshooting guides. Pick your faceplate for your system.
Evans Tempcon, Inc

[pkunk1]

The air door is operated by vacuum. You'll have to trace it back under the dash and find where it is chewed or disconnected. As posted above, the hot water to the heater core is controlled by a wire operated valve. The clamp that holds the outer case of the cable may have allowed it to slip out of adjustment.

[Horseshoe]

Be sure to check the connector on the vacuum canister also. I had the same problem you have and it turned out the vacuum hose was broken where it went into the canister behind the radiator support.

[LVJ58]

The OP didn't mention whether or not he was getting forced air out of the heater vents. If he isn't then sounds like a vacuum or vacuum servo unit problem. If he's getting air flow but it won't warm up, then sounds like a heater valve problem. Hopefully we'll get some feed back.

Safe travels...