1987 Thunderbird Heater Core & Blower Motor

[marksatterfield]

Hi,

I have a 1987 Thunderbird with a few issues with the AC/Heater system.

1) The Heater Core is leaking. I bypassed the heater core, but I'd really like to fix it. Unfortunately, according to the Haynes' & Chilton's manuals, I have to take the dash off and evacuate the AC just to remove the heater core! I've looked in the glove compartment and under the dash, expecting to see something that looks like a heater core or a door to the heater core, and all I've found is plastic. Called three shops, all shops want $550 ~ $700 to replace the heater core. According to one shop it calls for an 8 hour job to replace the core.

Has anyone performed the heater core replacement on the 1987?

2) The blower motor resistor pack burned out. I bought a new TCO (thermal cut off) for $2 at an electronics store and it worked for a bit, then burned out. I think what is going on is that the motor is drawing more power than it used to because it is old. I tore it apart, everything looks fine, greased it up, and still blew TCOs. So... I'm left with replacing the blower motor for $100 PLUS finding a resistor pack at a junk yard, or ... what are my other options?

I've considered making a PWM to reduce the power (instead of a resistor pack). Has anyone else used a PWM for this purpose? If so, any suggestions for the circuit design & transistor needed (specifically, how much power is this thing supposed to be using? Is a 10A transistor enough?)

Thanks for your consideration!

--Mark

http://www.marksatterfield.com

[Scrapper]

sounds like you have a short in motor so your going to have to take dash apart like there telling you and the book dosn't lie. sorry but either your going to have it done or try it yourself. only other thing you can do is shop around see if you can get it done cheaper. about $500.00 is cheap if that includes parts and labor but really dose sounds like a short in motor.....good luck....

[caddy11]

I found a place that would do it for $ 550.00 but the guy was short of me, pulling him over the counter. He need the car for two days and felt that I had the cause of the leak. Wound up with small hair dryer, and A/C adaptor for my in-car heater. Seldom use it, but in Texas it fits the bill.

[97Bird]

Mark, Check the fuse rating for your blower motor. A 1997 uses a 30A which is probably the case for your 1987. A 10A transistor is way undersized! Was the TCO rated for at least 20A? Worst case with blower on high 12V/30A= 0.4ohms for blower resistance. The resistor packs are usually 2.5-3 ohms with the lower resistor ranging from 0.25-0.5 ohms. Worst case with blower on setting just below High will give you 12V/(0.4+0.25)=18.46A going through the resistor pack's TCO.

[marksatterfield]

Thanks for the advice, folks.

So I don't want to spend $500 to replace the heater core. I'm in Florida, and I just pack the trunk with a few extra jackets for friends during the winter. Two interesting side effects: (1) With no heater, the AC is VERY cold and cannot be adjusted. To make it a little warmer, the AC has to be cycled. (2) With no heater, the defroster doesn't work. Bad for winter driving, lots of condensation settles on the inside with the windws up.

On the resistor pack, thanks for the current advice (that is, the "I" advice, Amps must be 20+). The TCO replacements were probably 10A. I'll be sure to buy a transistor that handles 30A+ when making the PWM.

--Mark

http://www.marksatterfield.com

[97Bird]

Enter pwm into your search engine and you will get a lot of info on pwm's. Here is one circuit that you would have to modify with a higher current FET. Go to the International Rectifier website to find one. Good luck with the project. http://www.solorb.com/elect/solarcirc/pwm1/
Here is another circuit that can be modified to work: http://www.discovercircuits.com/H-Corner/PWM.htm. Try using a type IRLR7807Z, IRLU7807Z or IRFR4105ZPbF, IRFU4105ZPbF FET. You will have to put the circuit into the airbox where the blower resistors are now located so the air can blow across the FET for cooling. These FET's are rated for 30A and 20A respectively at 100 degrees C