HVAC question.

[Davemcc]

There's something been bothering me about the heater on the Mark V. It has the auto climate control system, and it seems to work fine except when the slider is moved to the "heat" setting, which is to say floor heat only. The power to the motor just shuts off. The blower will run on any other setting except "heat" and that includes the floor/defrost mix setting. I thought that this may have just been a defect in just this one car, but my '88 Colony Park wagon has the exact same defect. It will not blow heat on the heat setting either.

Is this a common known defect on older climate controlled heaters, or do I just have two freaks from '79 and '88 that just happen to have the same problem?

Dave.
'02 Camaro SS
'00 Cougar
'79 Mark V
'88 Colony Park, POW, Held by body shop for insurance co.
'81 Fiat Spider
Former VIII owner.

 

[Frankie X]

RE: HVAC question.

This thread may be dead, but I thought I'd give it a try.

There's a switch in one of your heater hoses close to the
firewall that's referred to as a CELO switch- Cold Engine
Lock Out. Ford designed it to prevent the "Heat" mode from
engaging until the coolant is 120-140degF. The assumption
was that Floor/Heat is the only setting in which the customer
would never want AC modulation. You also don't get icey air on
your footsies first thing in the morning. Ford uses them to this day in certain model applications. It's fairly common for them
to stick open circuit.

You can't miss it. It has two 14ga. wires going to it and may have
two vacuum lines also. Disconnect it, jump the two wires, and
your blower will come on. They're still available at your dealer.