diagnosing heater issues

wigglesrewind

Registered User
hey guys i recently acquired a 92sc from another member here on sccoa. im loving the car but heater doesnt work. it has the climate control option and it acted exactly like my old 89 cougar did when the blower motor went out. when i turn on heat or ac or defrost or any of the buttons it makes a little pissing noise like air is venting. on my 89(no climate control) i simply swapped out the blower motor and it worked fine after that. on my sc i changed the blower motor and nothing changed. so i swapped out the heater control unit for another one. and it still did nothing. the climate control doesnt seem to be powering up or anything...nothing comes on the little digital display ever so i dont know what to think...i checked all the fuses in the fuse box and those in the engine bay. everything looks good so does anyone have an idea for me? now im thinking its the heater core but i thought when the heater core went out the blowermotor and everything still operated just it shot out room temperature air. at least thats what my old tempo did :)

any help is appreciated, im hoping its not a heater core but i guess if i have to i have to. i'll be taking out the instrument panel anyways to replace the speedo so i guess nows as good a time as any.
 
Climate Control Issue

Hello.

I to have issues with my Climate Control.If you open up the Glove box there are to stops on either side you can bend them back and the Glove box will open all the way, so empty it out before doing this.Behind you will see the Blower motor and below that there is a Controller for the Speed control of the motor ,this links to the Climate control this is most likey the culprit but they are expensive 149.00 From Ford I woul;d go to a Junk yard with it in hand you should get one for about 60 bucks.

Tecno. 92 SC






wigglesrewind said:
hey guys i recently acquired a 92sc from another member here on sccoa. im loving the car but heater doesnt work. it has the climate control option and it acted exactly like my old 89 cougar did when the blower motor went out. when i turn on heat or ac or defrost or any of the buttons it makes a little pissing noise like air is venting. on my 89(no climate control) i simply swapped out the blower motor and it worked fine after that. on my sc i changed the blower motor and nothing changed. so i swapped out the heater control unit for another one. and it still did nothing. the climate control doesnt seem to be powering up or anything...nothing comes on the little digital display ever so i dont know what to think...i checked all the fuses in the fuse box and those in the engine bay. everything looks good so does anyone have an idea for me? now im thinking its the heater core but i thought when the heater core went out the blowermotor and everything still operated just it shot out room temperature air. at least thats what my old tempo did :)

any help is appreciated, im hoping its not a heater core but i guess if i have to i have to. i'll be taking out the instrument panel anyways to replace the speedo so i guess nows as good a time as any.
 
a controller for the speed control of the motor huh? is it a wiring connector? wierd issue but i changed out my blower motor for a new one and my heater control unit for a new one and it didnt fix my problem, however i disconnected the battery for 30 minutes and when i reconnected it the heat worked for a day or 2. weird huh?
 


here i snapped a pic of behind the glove box, im guessing its the little one numbered "1" but am i correct?

what makes you say that the unit is the problem? do they go bad often?
 
can someone tell me what is shown in the pic labeled 1 and 2 ? thanks!

1 is the Blower Speed Control Module.

2 is the Chime Module, which is what goes "Ding Ding Ding" when your fries are - err, when there's a problem with something.

RwP
 
here i snapped a pic of behind the glove box, im guessing its the little one numbered "1" but am i correct?

what makes you say that the unit is the problem? do they go bad often?

Because it's exposed to water when the heater core leaks.

I've got one that's rusted and failed on my bench, planning to take it apart, reverse engineer the schematic, and repair (I have another one in my car, BTW - works a treat!)

RwP
 
thanks ralph i think my problem is #1 everything comes on but the blower, heat switch lights up temp light comes on but no blower probed the connector 2 wires going to the blower and they are hot but blower does not come on.
 
i think its called a blower motor final stage. it directly controls the fan speed and activation when asked to by the control unit.

think of it like a fancy variable speed relay. most (BMW in particular) will have battery voltage at all times with key on or key off and those little buggers have been the cause of many dead batterys over the year. but I am not sure on the exact wiring of the thunderbird but checking it is simple.

measure voltage in and check the ground to it and then if there is no voltage out its bad.

it might also run the controler in a loop situation but would have to see a schematic for that.
 
thanks ralph i think my problem is #1 everything comes on but the blower, heat switch lights up temp light comes on but no blower probed the connector 2 wires going to the blower and they are hot but blower does not come on.

Hmm .. if you've got the fully automatic temperature control (uses buttons, no rotary knobs), then there will be measurable voltage there at all times - just no current flow.

I had the same problem, but jumping the motor to 12V didn't make it spin up either, so I had to replace both the blower and the blower speed control module (BSCM).

BTW - To 90turbo1? It's a solid state switch that allows the EATC (Electronic Automatic Temperature Control) to vary the speed through the whole range. And the official name IS Blower Speed Control Module, at least in 1991. Just a minor correction.

RwP
 
Hmm .. if you've got the fully automatic temperature control (uses buttons, no rotary knobs), then there will be measurable voltage there at all times - just no current flow.

I had the same problem, but jumping the motor to 12V didn't make it spin up either, so I had to replace both the blower and the blower speed control module (BSCM).

BTW - To 90turbo1? It's a solid state switch that allows the EATC (Electronic Automatic Temperature Control) to vary the speed through the whole range. And the official name IS Blower Speed Control Module, at least in 1991. Just a minor correction.

RwP

yup same as how bmw has done it since late 80's.
 
The proper name is Blower Speed Controller and it is nothing more than a variable resistor, Instead of the regular 4 position resistor with the manual systems. They burn up alot. Always have with the Electronic Automatic Temperature Control systems. Even when they were new they had many problems. Not just in the MN12, but in all Ford/Lincol-Mercurys with EATC....Normally they default to the highest setting when they are on the way out. Sometimes not though....
 


here i snapped a pic of behind the glove box, im guessing its the little one numbered "1" but am i correct?

what makes you say that the unit is the problem? do they go bad often?

well the blowermotor was bad got one at the pick and pull but they didn't have the BLOWER SPEED CONTROLER as shown in pic #1 so does anyone know where to get them i've had no luck finding one THANKS FOR ANY HELP!
 
well the blowermotor was bad got one at the pick and pull but they didn't have the BLOWER SPEED CONTROLER as shown in pic #1 so does anyone know where to get them i've had no luck finding one THANKS FOR ANY HELP!

I got lucky and found one.

There's several MN12s with EATCs at the local u-pull-its, but those, being electronic, are sold with no warranty express or implied (i.e., "We have your money, now get the heck outta here!") Plus, I'm not sure they have the modules still.

Hmm ... Might need to pick them up and start rebuilding them, seems to be a weak spot (at least partly since if the heater core starts leaking, it'll take them right out.)

Can't offer much except to check and see what other Fords use it (using the interchange list at the u-pull-it). There's a later model that fits, but needs a new wiring harness - it was used in Explorers and Lincolns and Crown Vics around 2000, I don't have the part # but I bet you can find it with a search here. If not here, check over at http://forums.tccoa.com and search there too.

RwP
 
Back
Top