I have a 1975 450 slc, and the heater won't turn off. Is something else wrong other than the heater? It also runs sluggish...

Thanks C.M.

I had the same heater problem. It was the monovalve, I think its called. At any rate, its a valve that sits in front of the heater blower cover in the engine compartment. It was a couple of hundred dollars or so to get it replaced. I was also told that sometimes the control levers get stuck in the on position, and that this is a major hassle to fix.

micro-switches on heater controles
If the car has eletronic fuel inj. it probibly has the old style slides in the console.These work vac. switches that turn off the hot water.
The defroster doors stick letting a/c air fog the windshield,major repairs in store.
A manual valve installed at the firewall will help.

Thanks for the info.

C. Mariscal

AAL,

If you paid a couple hundred bucks to replace the heater valve, as you described, get a new mechanic. These valves are about $40, take less than 30 minutes to replace and the job is easy for a do-it-yourself'er.

Steve Guilford
107 026 12 000677

I need this done on my car, thanks for the info. I won't be doing it myself and it is good to know how much it should cost!