Heater/AC motor not blowing

[sntrym95]

95 ECSB 5.7L auto.

Ok, here's what it's not:
Blower motor
Control unit
Blower motor resistor
Hi blower relay

I've replaced or tested all of these pieces. When the blower is on high, I get no voltage at the blower motor. When on any other setting, .8 volts or so.

I'm stumped. The fuses look good too. I have power at the control unit (it's brand new, and I've tried 3 different ones with the exact same results.

One thing to note: Before it completely stopped working, it would work for a bit then stop for a bit. Once off for a while, it would then start working again.

I'm thinking there's another component somewhere that isn't listed on the schematic I have from the Haynes manual.

Help?

Thanks!
Mike

[speedygonzales]

Have you tried hitting the motor with foot/piece of wood etc?

[sntrym95]

yeah nothing. But I'm not getting any voltage there so that's not it.

[ChevLoRay]

All of the grounds are good? Since it was "sometiming" before, it sounds like a poor connection "somewhere". The fact that you only got 8/10 of a volt (.8), then some minute amount of voltage is finding a path through that "somewhere" connection.

Whatever it is, when you find it you'll surely say something profound....

[dragginmetal]

I'm looking through other wire diagrams. On the Blower Resistor, do you have dk blue, lt blue, tan, yellow or yellow, tan, and (2) purples?

[sntrym95]

@ChevLoRay - yes, it will be something profound, and likely profane. I'm sure it's a bad wire or a sensor of some kind. There's an AC disable listed in the schematic for my truck that's on the control unit but I have no idea what that's for. I also suspect it may be the voltage coming from the ignition but can't be sure just yet. I'm going to pull the control unit again and get in there with the multimeter to find where I'm not getting voltage where I should be.

@DragginMetal - dk blue, lt blue, tan, yellow I think. I'll check today.

[dragginmetal]

The AC disable is the button on the front of the controller labeled A/C. It lets the fresh air in or recirculates the air. The same as "Max A/C" settings on other autos. It open and closes the recirc door.
The diagrams i have are basically the same as haynes. The A/C one is a little different.

air-conditioning-heater-circuit-1-of-1.pdf
air-conditioning-manual-a-c-circuit-1-of-1.pdf

[sntrym95]

Yeah that's the one I have. I think I have it narrowed down to the ignition switch. I was able to get 12 volts to the blower motor with the ignition switch partially on but not all the way on. Guess I'll get a new one then go from there.

[RayInAlaska]

It sounds like the power connection going to the blower motor is intermittent. Most times the reason for things like that is a loose connection along the way. Since you think the ignition switch may be bad, before removing it I would just turn the switch for the blower motor to high, and then listen for the motor to come on/off when wiggling the ignition switch after it has been turned ON to power the blower motor. If the connection through the switch is intermittent, you should hear the motor coming on and going off again.

Summary:

a. Turn the heater switch to high
b. Now turn the ignition switch to ON, and wiggle it to see if it cuts power to the motor

If it cuts power to the motor when you slowly wiggle it, then the switch is the culprit. If it does not cut power to the blower motor, then check for loose connections at all connecting points between the ignition switch and the motor.

[sntrym95]

Well I replaced the switch and still no power to the blower motor. On Low, Med1 and Med2 I get .5V and on high 0V. So there's definitely something in between the ignition switch and the controls that's wrong, but I think that's going to warrant a partial dash removal. Ain't nobody got time for that. It'll have to remain like this until then.

Also, if someone has a better schematic than the one in the Haynes manual I'd appreciate it.

[OrangeAnimal]

What happens if you wiggle the connector at the Ign switch? You should probably try the same at the control panel. Work backwards from the motor and at what point do you have 12v. You may not have 12v going into the control panel. Do all the blend doors work?

[sntrym95]

The blend doors don't work, so I know I don't have 12v coming into the control panel. That's why I replaced the ignition switch. The truck has 255k on it so I know stuff is wearing out. The problem is that the schematic I have is very vague when it comes to these wires. I might hit up the library for a Chilton but was hoping someone here had one.
Posted via Mobile Device

[LynnJr]

If the blower motor has a wire ground on it like my 1990 remove it and clean it up and replace it.
Mine acted like the controller wasn't working and it was the ground wire.
Lynn

[Macster]

My sons 1991 C1500 2WD blower motor only works on High position, I have yet to find the problem:

Changed Resistor and Heater/AC Control; still not fixed.

I will try and locate the ground wire for blower and check that.

Keep up the posts; I have been working this issue on and off for over a year!

[sntrym95]

Finally fixed it. Behind the glove box is a connector wrapped in foam that is a constant hot to the relay. It contains a ground that is used for both the blower and the actuator doors. At some point it melted partially and was no longer connecting either wire. Clipped out the connector and replaced with crimped butt connectors. Voila! Ran an extra ground off the blower wire ground just in case while I was in there.

Moral of the story: The factory service manuals are way more helpful than the Haynes manual when it comes to electrical troubleshooting.

[sntrym95]

Speaking of the factory service manuals, I took some pics at the library for the others who are having similar issues:

http://www.flickr.com/photos/99167717@N06/

[stevejohnson48]

sntrym95,Mike as to your reference book do you have a CARD CATALOG number to the one with the schematics in it ( Its hard to read in the pic's) ??/ With all the trouble you had on this project did you control panel read out ever do funny things like on mine all the arrows come on blinking and also do you think the ground wire that you fixed has any thing to do with the ground side that would relate to the control panel read out or its functions ??/ Steve, Some body told me that there was actually a ground wire for the control panel that's tied into the ground wire at the head light switch ??/ I was under the impression that the head light switch doesn't need a ground wire ??/ Why would it every things grounded after any light that there is on the vehicle ??/ Except the light switch location light that's in the dash lights ??/ Again Steve

[stevejohnson48]

Originally Posted by sntrym95

@ChevLoRay - yes, it will be something profound, and likely profane. I'm sure it's a bad wire or a sensor of some kind. There's an AC disable listed in the schematic for my truck that's on the control unit but I have no idea what that's for. I also suspect it may be the voltage coming from the ignition but can't be sure just yet. I'm going to pull the control unit again and get in there with the multimeter to find where I'm not getting voltage where I should be.

@DragginMetal - dk blue, lt blue, tan, yellow I think. I'll check today.

I'm starting to think that reconnecting all the ground connections would be a good start ( splice into all ground wires and butt and eye let to a new ground location ) There's two main locations possibly 5 depends on where you pick them up at ??/ I guess I would try and pick them up ( New Ground wire's) as close to component as possibly??/ To bad they don't give ohmage states VS resistance by dimension Per say on schematics ??/

air-conditioning-heater-circuit-1-of-1.pdf
air-conditioning-manual-a-c-circuit-1-of-1.pdf