rear AC blower

[kebauc]

The rear AC blower does not work. I took off the interior panel to get at everything. When changing the fan speed switch, there was an audible click from the relays in the resistor changing position. There was no voltage on the connector to the blower motor.

So, I replaced the resistor module. Still have the clicks (good), I have 12V on the output (also good), but no motion from the motor.

Does this mean the motor is bad as well? How can I confirm this, without buying a new one?

Thanks.

[777stickman]

Welcome to the forum. Need year, model and eng size!!!!!!!!!!!!!!!!!

[kebauc]

2003 1/2 Ton Suburban.

Note sure why engine size matters, but it is the basic V-8 GM sticks in these. I gave up keeping the size designation straight when everything went to liters. I guess it translates to 350 or so.

Also, i forgot to mention, this is a 100% manual HVAC. No automatic climate control here.

[777stickman]

If you now have 12v at the fan motor the only other thing is to check for a good ground at the motor connector. If that's good then it sounds like the motor is bad.

I only have manuals up to '99. Your '03 has what is called a BCM (Body Control Module) that may have some control over the HVAC system. Also in my '99 manual I see slight differences in components depending on model (K vs C) (1500 vs 2500) (and engine sizes). That is why I asked for all the info.

Good luck.

[kebauc]

Help!

I got a new motor. No luck.

I have 12V on the pigtail that connects to the motor. The blower switch also turns the 12V. This tells me the switch is good, the resistor is good.

I am ruling out a blown fuse because I should not get 12V.

The connection to ground seems solid as well.

I am about to take this one into the dealer for repair, so any last minute suggestions would be great.

[777stickman]

Just because you have 12v at the blower plug doesn't mean the fuse will handle the amps when the motor is hooked up. Also, if the resistor pack is working properly the voltage should be something less than 12v at the lower fan settings.

Run a jumper from the batt to the 12v + terminal on the motor. Hook another jumper from the motor ground terminal to the ground signal in the plug. See what happens, but don't run it for long as this setup is not fused.

Once again, I'm an "old body style" guy and don't have a BCM.

Hopefully some of the guys with newer model experience will step in and help out.

[kebauc]

I can "adjust" the voltage by changing the fan speed.

The motor is good, I did exactly what you suggested (in fact I returned the new motor, after confirming the old was was good).

I hooked up a test light to the resistor pack output along with an ammeter. I could not draw enough current to do anything. I did check the ground path and got a resistance of about .1 ohm.

My guess now is that there is a bad connection/component somwhere on the hot side of the circuit and power just can't get to the blower.

Does anyone have a wiring diagram?

Thanks.

[emt1134]

Put the switch on high, connect one of your voltmeter leads to power and the other to the black wire on the 2 wire connector that connects to the blower motor. see if you read 12 volts..

[kebauc]

I get about 9.5V with it in that position. I had attributed the voltage drop to general wiring and voltage drops designed into the system.

From your post, I am guessing this is not the case.

[emt1134]

c

[kebauc]

I keep getting the ground as a suggested problem. Let me put that one to bed for good.

I can run jumper directly from the battery to the motor. By jumping the motor ground to the motor connector ground, I get the motor to turn.

Also the resistance from the motor connector ground to battery ground, comes in well under 1 ohm (on the order of .1).

The diagram is real nice. Do you have a wiring diagram for the HVAC?

[kebauc]

I got my hands on a wiring diagram and made a few notes on it.

There are a couple components i cannot locate. Does any one have a general idea?

Link to my sketch -

http://kebauc.googlepages.com/home

[emt1134]

This is hard since I cannot see what you are doing...

- Test your voltages with the vehicle running, so you know that the decreased voltage readings are not due to the battery draining as a result of the alternator not running.

-Make sure the blower switch is on HIGH

- Make sure the positive lead on your voltmeter is reading batter voltage, should be around 13V since you have the vehicle running now

-Put the other lead on the ground terminal of the connector on the resistor module that connects to the blower motor... Now you should see that same 13V or so... Tell me what the reading was before you connected to that ground circuit, and after.

[kebauc]

You are right, this is hard to do in text form.

All measurements in this post are with the fan on high and the engine running.

The meaurement from the + output of the resistor module directly to ground (body of the truck) only goes up to 10.8V.

The meaurement from the + output of the resistor module to ground on the same connector also comes in at 10.8V.

The same measurement on the + input of the resistor module to ground measures the same 10.8V.

Directly across the battery terminals I get 13V.

I checked the cig lighter and got the expected 13V, just to be sure there isn't a generic voltage problem.

I am not sure what you mean by "tell me the reading before you connect to the ground circuit", but I think I covered it in the above measurements.

[emt1134]

Ok, now we are getting somewhere.. This means, as what you have determined previously, that we can rule out a ground issue.. Now we'll concentrate on the power side of the circuit.