heater fan lost power.

Topic: heater fan lost power. (Read 7437 times) previous topic - next topic

heater fan lost power.

February 04, 2014, 02:14:55 PM

On my 86 cougar, only the high fan position worked. One day while i was driving, the fan shut off. How does the fan controller work? Im guessing it has a wipe on a resistive wire, similar to the dimmer switch. This would explain why only high worked before.

Fuse is good, have power to horn ect as well. Am i looking at a new heater control? Is there a wire i can temporarly jump or wire in a switch to get me by a month or two till it warms up a bit?

heater fan lost power.

Reply #1 – February 04, 2014, 04:53:34 PM

Only the high position working is the blower motor resistor. I'd put money on the blower motor itself going out before the controller.

heater fan lost power.

Reply #2 – February 04, 2014, 04:58:08 PM

I have a NOS switch for an 86 cougar that I will never use, PM me if you want it.

heater fan lost power.

Reply #3 – February 04, 2014, 05:22:22 PM

The blower will only work on high if the "thermal limiter" is blown. The limiter is part of the blower resistor unit mounted on the air box.
Fuse 9 is only used by the blower, nothing else.
The resistors are not used in the high speed position. The speed selector switch could be bad. You could try grounding the Orange/Black wire at the speed switch.
More diagrams in a few.

heater fan lost power.

Reply #4 – February 04, 2014, 05:26:50 PM

I also have the part listed above, also NOS.

heater fan lost power.

Reply #5 – February 04, 2014, 05:52:44 PM

It may be easier to unplug the cable from the blower resister on the air box.
You should have voltage on the orange/black wire with the key on and the function switch in any position except OFF.
Grounding the orange/black wire should make the blower run.

heater fan lost power.

Reply #6 – February 04, 2014, 10:08:12 PM

Sweet. Thanks guys. Hopefully its just the resistorso I can jump it. If its not, not worth the trouble to have a working heater right now.

heater fan lost power.

Reply #7 – February 04, 2014, 11:23:54 PM

Quote from: V8Demon;428374

Only the high position working is the blower motor resistor. I'd put money on the blower motor itself going out before the controller.

Not really
Quietleaf and a few of us did some observations and rewiring to the manual controls of the heater assembly

Quietleaf found that the controls themselves on the connector would get very burnt and possibly catch on fire

Hopefully it is an open circuit down at the controls otherwise the blower motor it's self or the resistor assembly has burnt open

Good luck haystack
By the way I don't have one single set of manual heater controls but a few other guys have already replied

Wish I could pay back the favor

heater fan lost power.

Reply #8 – February 04, 2014, 11:34:56 PM

By the way a 26 or 28 gauge short chunk of wire soldered in place of the thermal limiter could stand as a decent repair

Or you can just go to RadioShack or some other electronic supply house

I have a couple of threads about this in my DIY link below

heater fan lost power.

Reply #9 – February 05, 2014, 02:13:20 AM

Just to clarify a little, you have two problems.
1. Only runs on Hi, is the thermal limiter on the blower resistor unit blown.
2. Not running on Hi. This has nothing to do with the resistor. You can remove the resistor unit and it should still run on Hi.
It is probably the motor, but you can make some checks to make sure.
If grounding the O/BK wire in the plug to the resister makes it run, the blower speed switch is bad.
You can check for voltage coming into the motor at C275 the DB/LG wire.

heater fan lost power.

Reply #10 – February 05, 2014, 07:21:34 AM

I agree on the resistor, either the thermal limiter is blown or the or the medium high element is open. In either case, the part is stupid cheap, so don't cobble and hack your way around it, it isn't worth a vehicle fire. Second, it has to be mentioned that for the thermal limiter to be open, the blower would have had to be overdrawing the circuit. Since you ignored it, and kept using it exclusively on high, you now probably have a blower switch burnt from being overdrawn for extended lengths of time. You can replace those 2 easily, but you still have to address the root cause, which is most likely a bad blower motor. This is what would be referred to as the causal part, and parts went down one by one due to neglect and the in-range failure of the blower. Had you replaced the resistor right away, you would most likely have had the thermal limiter open on the replacement almost right away. No easy way to say it, but you're pulling the dash in any scenario that includes getting system function back.

heater fan lost power.

Reply #11 – February 05, 2014, 08:38:01 AM

if you find your blower motor did survive,, and its the controls for either or both speed and selector.. here is a diagram to solve this for ever.

just repin wires in the areas shown, add relays and protection.

heater fan lost power.

Reply #12 – February 05, 2014, 11:39:34 AM

Quote from: jcassity;428393

Not really
Quietleaf and a few of us did some observations and rewiring to the manual controls of the heater assembly

Quietleaf found that the controls themselves on the connector would get very burnt and possibly catch on fire

Hmm. Never seen that before. Is there a thread on it? Would be interesting to read up on.

heater fan lost power.

Reply #13 – February 05, 2014, 11:46:40 AM

If the blower motor itself has given up the ghost, bring the old one with you when you go to grab a new one. The parts # listed for these was NOT what was in the case; at least not in mine which has the ETC. I don't envision there being an actual different blower motor for ETC cars, but hey, it's possible.

Anyway, the one that many parts stores has listed would not even come close to fitting. IIRC The correct one had a Ford part # that started with D8.....

heater fan lost power.

Reply #14 – February 05, 2014, 05:58:56 PM

I disagree with the theory that an over current situation blows the thermal limiter.
The reason the blower resisters are mounted in the air box, is because they get very hot.
The reason they use the open coil type resisters is so the air moving through the box can carry the heat away.
Low or no air flow will allow the heat to buildup around the resister and blow the thermal limiter.
An over current situation will blow fuse 9.