Hello! Fist time poster and brand new member. Wonder If I could get some help? My Mom's 1987 Grand Marquis is a great car but the heater is not working. When you switch it on, the "floor" setting will cause the blower to stop all together. All other setting work but no heat. I was trying to get it ready for winter. The heater core seems ok so I'm figuring it's a sensor somewhere in the auto climate control. Any ideas? Also, can you just bypass the valves on the hot water lines to the heater coreand have a normal operatingheater?


Also, Google was no help. Found one guy who had the same problem and called it a"heater temperature sensor". I'm figuring this is the ATC sensorsince Ford has never heard of it either.Edited by: stump_breaker

Yes you can bipass valve (but why), try replacing a/c control panel, with one from salavage yard. good luck

Thanks for the quick reply!


You think I would need to change out the whole control panel? I thought it would just be a sensor. And I was thinking you could bypass the valves to keep this from happening again but I see your point. Doesn't not having coolant flowing through the heater core all the time cause the core to rust up andgo out sooner? I'm seeing on the web where a lot of people have to change out the heater core in these cars. On her car there are 47000 original miles - literly the little old lady who drove it to the store and church story - and the core still seems to be ok for now. Of course in Texas we don't use a heater but about 1 month a year (LOL).

The temperature sensor on you 1987 Grand marquis is locate on one of the heater lines in the engine compartment.. It will blockk power from your blower motor until the enginer coolant reaches at least 105 degrees. It you lose your blower when in heat mode try that first. You donot need to block or bypass any valves in you heater system. The only heater valve should be a vacuum operatrd normally open valve that shuts off the flow to the heater core during max ac modes.


If the engine is already warm and the blower stops. try replacing the sensor( also called a cold shut off switch).


Hope this helps.