AZ455

Looking for suggestions here from anyone who has experienced a similar issue. I followed all the diagnostic flow charts in the CSM for the high blower relay and everything pointed to new relay. I replaced it this morning, still no high speed.

Here is the interesting part. I pulled the controls out of the dash, put switch in high speed position, I get 12v at the orange wire. Also with it on high I get 12v at the orange wire at the relay, and you hear the relay click. I also get 12v at the black with white stripe wire that goes from the relay to the resistor on the heater box. I also have 12v going to the relay from the junction block. Still no high speed though, what I do hear is the constant very low blower sound like when you turn fan off/key on.

Any ideas of where I should look next? Maybe the blowers high speed is bad (seems almost impossible)? Which wire goes to the blower motor to supply it power for the high speed? Purple wire from heater box? If so it's got 12v also.

Thanks.

AZ455

Forgot to mention...

At the back with white stripe wire that goes into the resistor from the relay I get these readings with the fan switch in each position:

Switch ---- Voltage @ Resistor (black wire)
OFF ------- 3V
LOW ------ 5.5V
MED ------ 7.75V
HIGH ----- 11.2V

So the voltage increases when the relay clicks going into high speed, however the fan slows down to the same speed it runs at in the 3V off position. The resistor is OK, each of the other 3 terminals shows a slightly reduced voltage in each switch setting.

What I am not understanding is if the voltage is there in the HIGH position, why does the fan slow down?

These voltages are low because this test was done with the engine off and with a battery of questionable charge.

MDchanic

You've got some sort of a dirty connection there, I think.

You need to get to the blower motor (easiest way is by removing the RH fender liner), disconnect the big purple hot wire and the ground wire, check and clean them, and then move back from there.

Try putting a hot directly from the battery to the hot terminal of the motor - it it's well grounded and it spins over very fast, then the problem is in the wires leading to it. If it doesn't, then you need to oil the bearings or replace it.

- Eric

AZ455

I can try that.

I don't know though, the motor runs very strong on the medium setting right before high, puts out plenty of air, runs smooth and quiet.

If I probe the purple wire to the blower motor it's a constant 12V I believe?

It doesn't make sense to me. Why would the motor slow down once it receives 12V. Maybe my wiring diagrams are incomplete or I am not looking in the right place, but why is the purple a constant 12V at any setting? Where do the wires from the resistor go, to the fan switch?

AZ455

Was just thinking, my Olds has the Tempmatic system I believe.

Will the HI speed not work under certain conditions with this system? Engine off, coolant below 120F, etc...

MDchanic

I have no idea how the Tempmatic works, but if your blower motor is getting 12V, it should be spinning on High, no ifs, ands, or buts.

If it's not, then it's not getting 12V.

- Eric

1970cs

I agree with Eric, by getting the purple wire off at the blower motor and test at that point with key on and switch set to high you should have 12v
If not then you have a voltage drop, replace wire! If you do have twelve volts, then run a jumper wire from a 12 volt source and see if it spins at rate speed! if not replace blower motor.

I could not access the wiring diagram for 1974 CSM website seems to be down? I have a 1970 CSM I am not sure its the same colors and styles as 1974

Good luck Pat

Allan R

ding ding ding....WINNER!
I think you just hit the nail on the head. I had a car with the tempmatic AC too. The fan would not run except on low until the coolant reached temp (think it was around the 120 you stated). In that case, fire up your car till the engine gets warm and see if your problem goes away.

AZ455

As I said, there is 12V at the purple wire. What I am confused about, is the voltage raises/drops at the resistor in the heater box as I go through the fan settings, but stays a constant 12V at the purple wire? Yet the fan never comes on at full.

That I shall do. Probably tomorrow. Oh, and the window weatherstrips should be here tomorrow, if I have the opportunity I will install them and snap a few pics.

hookem horns

I know nothing about Tempmatic, but I had similiar problems that cleared up by cleaning the ground at the firewall. Easy to try before pulling the inner fender

Allan R

Don't shoot me if I'm out of line, but I'd bet that if you traced the wiring to the controller for the tempmatic, the logic board would override the voltage until it recieves a signal from the temp sender...If I'm right we'll call it a lucky guess.

Perfect! You da man! BTW don't break the glass taking the chrome off or you're going to be driving around with a plywood window.

Lady72nRob71

Or the motor ground is bad or the bearings are shot.
I have had motors that ran at lower speeds okay but on high, the shafts wobbled around and RPMs went down.

AZ455

I guess I will have to pull the fender liner and run power straight to it to see what's really going on down there. Also clean the ground like 'hookem horns' said. Fortunately I have never NEEDED High, I just like all my junk in working order.

I wouldn't doubt that the Tempmatic is overriding it. I did read some of the section in the CSM on it, it can/does do that in some situations.

I'm not sure the chrome needs to come off after having a look, just the moulded rubber ends of the back door seals. I'm not sure if it'd be the same on a two door, but I will get up close pics anyway. If I don't get to it tomorrow I will by next Tues/Wed. My next semester starts tomorrow morning, looking forward to this one, all on Automatic & Manual trans/transaxles, drive lines/diffs.

MDchanic

Bad feed = "not getting 12V"
Bad ground = "not getting 12V"

Resistance anywhere in the circuit will have the same effect at reducing current flow.

My thought on this subject was that if he had a resistive connection that was subject to heating up, it could pass a smaller current, but then heat up under a larger current and not allow sufficient current through to give a "High" speed.

I think we were trying to say the same thing.

- Eric