Help with Heater Dianosis

CrossT · 01-23-2003, 06:16 PM

The fans for my heater do not function; neither the one in the engine compartment nor the two in the cabin.

I do get some small amount of heat when the car is moving, but I assume that since the blower in the engine compartment is non-funtional, that it is just blocking the heat. The good new is that it appears the the heater boxes work as I can turn what little heat I get with on and off with the two levers.

I am puzzled as to the function of the rotary switch between the seats. The manual shows something different that what is in the car. My switch has four positions; off, 1, 2, 3 (the manual refers to settings 1-10). I assume the knob is to control the speed of the fan(s), but nothing happens whether that levers are up or down.

The bottom line seems to be that the systems is ok mechanically, but electrically it is non-functional.

Seems hard to believe that all the fans are bad, so I am thinking that the relay in the engine compartment is probably to blame. It is a pricey item, so I want an opinion or two before I go further . . .

The car is an 86 coupe

thanks for any suggestions/help,

Todd
=-=-=-=-=-=-=-
86 cpe

JDaniel · JDaniel's Garage

The off 1-2-3 dial is for manual heat. The 10 position is for cars equipped w/auto heat.

If you lift the levers and the motors don't come on check to see if you've got power to the engine compt. blower. Then check the blower to see if it's burned out... then check your switch in the cabin (inside the box where the heater levers come out from).

Argo · 01-23-2003, 07:03 PM

The footwell blowers don't run unless the engine blower is running. Check the engine blower for power (when the levers between the seats are pulled up, key on or engine running) - just pull the wire connector straight off; brown wire is ground, yellow is hot. If power is there, the blower is probably toasted - common occurence. If no power, check the relay. The rotating dial operates the footwell blower speed to assist either window defrost or cabin heating.

Argo
88 Targa

CrossT · 01-23-2003, 07:24 PM

thanks guys. you've given me good infor here wrt diagnosis of the problem. i have one more (operational) question. how do the levers and the dial interact, or do they? what does what?

APKhaos · 01-23-2003, 07:38 PM

The lever-actuated switch is the 'master'. It switches power to the engine blower, and the engine blower ON switches power to the multi-position switch via the heater blower relay in teh engine bay panel.

The multi-position switch controls the speed of the footwell blower fans.

In short, the engine bay blower must be functional before anything else will work. A bizarre design, but there it is!

Roy M · 01-24-2003, 12:29 AM

Todd

I've always found these useful

http://www.type-911.co.uk/images/exhausts/heatingtech1.jpg
http://www.type-911.co.uk/images/exhausts/heatingtech2.jpg
http://www.type-911.co.uk/images/exhausts/heatingtech3.jpg
http://www.type-911.co.uk/images/exhausts/heatingtech4.jpg
http://www.type-911.co.uk/images/exhausts/heatingtech5.jpg
http://www.type-911.co.uk/images/exhausts/heatingtech6.jpg

Once you understand the system it actually all makes sense (and I can get what I want from the heater in normal driving now!)

thrown_hammer · 01-24-2003, 02:44 AM

Roy,
WOW! Good stuff. I have a '73 with ann '86 3.2 engine in it. The passenger compartment blower works but no heat.

I don't know if the engine compartment fan works, I will have to check it with a voltmeter. All the duct work and flappers are there and the heat worked before the engine swap according to the PO. I wasn't sure where to start, but now I have at least some drawings of the system.