FatCat

I pulled the console to do some other work an while I am there I need to see if I can figure out why my rear defrost and blower motor doesn't work. I have already pulled the motor and tested it is good. Here are pics of the wiring on the control head. Can anyone tell me what to check?
Thanks!

FatCat

FatCat

Ttt

FatCat

TTT I hope to get some help before I go ahead and put it back together.

CaseyJones

Did you check the wiring at the fan motor for power? My fan resistor was damaged and the fuse was blown. Also, the link to the heating element in my rear window was separated at the wiring harness in back so my rear defroster didn't work. Still working on that one.

Easy Mike

Rear defrost was optional and had a separate switch. It is not part of the regular HVAC controls.

Capt Ken

Everything looks connected properly. While you have it out do you have power to the switch? Does the switch work correctly? You didn't say which fan motor. The rear defrost or the main heater fan. Do you have power through the switch to the fan? Basic multimeter detective work. You also don't say which year of car. Some C3's just have a fan that blows air on the back window to defog, no heat. As Easy Mike said it has a seperate switch. If you have elements in the window, it probably has it's own push off/on switch.

7T1vette

Rear defrost heat/blower is activated by a separate switch on the driver's side of the [lower] transmission console.

FatCat

I have a 78, and the rear defrost is a separate switch with the element in the window. I have not checked any wiring because I will need to know what to check. I am a little challenged in the wiring dept. HAHAHAHA! Well I am challenged in most areas. ;-)

FatCat

Ok more pix, this harness runs to the blower area on the car. I do have power to it but I am not quite sure where the connectors go. Can anyone help?
Thanks!

FatCat

Ttt

FatCat

Ttt

speedreed8

the plugs with green wires: the rubber 90° plug goes to a pressure switch on the ac line, the straight plastic plug connects to a temp. sensor on the evaporator line.
the round plug with black wire (capact.) its power for blower motor, and the single straight black plug is ground for blower motor.

FatCat

Ok I got power and ground and the blower motor is working. Here is the issue I need help with!

When I hook up to the blower motor, is blows lightly but if I hook it straight to 12 volts, it blows hard.
The switch in the car has no effect on the blower. Hi to low is all the same and in fact, it blows by just turning on the key.
The other problem is most of the air blows out of this vent in the wiper area.

Any input will really help. I am trying to solve this before I hang the compressor this weekend.
Thanks!!!
FatCat

FatCat

Ttt

79vetter

Willcox has a video on how to check your blower switch on the A/C controller.
Its normal for it to blow on low with the key on.

FatCat

Thanks! I will se if I can find the video. Any idea why most of the air blow out of the vent I posted the picture of?

79vetter

Your fan motor is located down in there past that plastic screen. I don't know how air could come out of that area. Take that screen off and shine a light down there - you will see the fan blades.

FatCat

If you can see the fan blades wouldn't that mean it is open and air flow out of it?
Scott

LudemJo

I have been investigating the whole HVAC thing on my 74. Mine does not blow out of the vents either even though I can hear the fan changing speeds when I move the switch to the different positions. If you look down in the fender on the passenger side of the windshield wiper trough you will see the fan. I believe (and I am no expert) that one of the doors in the HVAC system under the dash are jammed in a position that does not allow the air to flow out the vents. I need to dig into this as well, but am going to wait until I am ready to shut down for the winter before tearing into the dash. I am worried that once I tear into the dash I will open a big can of worms that will keep the dash open for several weeks...I don't want to lose the driving time right now.

I will be interested in whetever you find out...I will be in this boat soon enough.

John