scrappy76

The other day I went out to charge my a/cUp. I started the car, let it warm up. I put the AC on, turned up the fan to 10. All working good went out and hooked up the can of freon an started filling up the system. Once the gauge was in the green, I disconnected the can and went inside the car to see how it felt and the fan was not working. I checked the 5 amp fuse marked ac fan and it was good. I went under the hood and checked the 30 amp fuse for the blower and it was good. I went ahead and disconnected the battery for a minute then hooked it back up just in case something needed to be reset and still a no go. The fan does not work at all, ac or heat. What do I check next ? Is there another fuse? I want to also add that the clutch is kicking in, so the AC is working, just can't get the fan to blow.

WVZR-1

Before someone else asks!! What year?

'94 comes to mind!

I'd maybe just put 12V to the blower motor and see if it runs. C68 and the blower module diagnostics I don't recall as being very straight forward. There is diagnostic trees in the FSM and I believe you've got one> Yes?

How have you been?

Red86Z51

I fixed this same exact issue on my '86 this spring. In my case, the blower control module located in the top of the blower box was bad. The module is responsible for fan speed control in the C68 system. The easiest way to check it is to see if the line going to the blower motor reads 12V on fan speed 10. Mine did not, nor did the voltage drop as I reduced fan speed which told me the control module went south. Put in a new one and now all is AOK.

scrappy76

It's a 1994, sorry about that. I will turn it on and check the voltage to the motor and get back to you guys.

WVZR-1

Jumper 12V to the motor to confirm run. There's programmer fuse. Check voltage @ PPL & the RED @ the module maybe.With the wiring diagram maybe someone with a '94 can factually lead you through diagnostics.

scrappy76

Ok. Ran 12 volts to blower, works good. Checked connector to blower, no voltage. I checked all the fuses in the fuse panel that has to do with the fan and a/c. And found there is no voltage at the a/c module fuse.
So we have no voltage coming out of the blower connector and no voltage at the a/c module fuse.
Where to next?

belairbrian

Reading the schematic, A/c MDL Fuse 1 will only have power if the Blower Power module blower control output has power.

My suggestion would be to turn the system on and back probe the blower pwr module at connector c2 pin A (ppl wire)
Also check connector C1 pin B (red wire). Suspect ppl will have nothing and red will have 12V.

If that's the case then the blower power module is no longer processing inputs from the HVAC programmer or the programmer is not supplying a control signal to the blower power module.

scrappy76

What is the blower power module, and where is it?

scrappy76

I have the fsm books, trying to learn here also

scrappy76

Looked online. I think I have found the module. I am looking online now. I am going to test the wires after lunch. I will let you know. Thanks.

belairbrian

For future reference,
The blower power module is mounted on the evaporator housing, passengers side. See fig 12 of the component locator pics in the FSM

Page 8A-66-5 is a surprisingly good explanation of how the C68 fan speed is controlled.

But basically the head unit sends desired blower speed to programmer over the data lines. The programmer sends a variable signal to the power module which in turn sends variable voltage to the blower.

The signal from programmer to the power module is a low power control for higher power feed to the motor.

Voltage to the motor is variable at 4-12vdc.

scrappy76

Well I tested the red at the module and good there. I turned the ignition on and the a/c on, set the fan speed At 5, then tested the tan wire and was getting 6.97 volts.
So I am going to assume that the blower module is shot.
I will look for a good deal on a new one. Pretty expensive item for a guy on a bologna budget.
I will let you all know when I am done.
Grazie.

scrappy76

I guess the other day I was wrong about having voltage in the red wire going to the module. I just checked it now and the red wire is dead. I tried with the key on and off, no voltage. I read that the red wire goes to the starter, but I put the Vette on ramps and looked and I cannot find a red wire at the starter. Is it different for a 94 or am I blind? Help.

WVZR-1

Under-hood box #1 Fuse #4 I believe. See the diagram I posted several days ago. 'lower right'!!

scrappy76

I am reading the fsm, and it looks like the red wire is going to the 30 amp fuse in the under hood fuse block next to battery. Is that correct?

scrappy76

scrappy76

Ok. The fuse looks good. I also put a test light on it and voltage is coming out both sides. So I decided to run a jump wire from the blower module prong where the red wire connects straight to the battery and the blower fan came on.😎. So it looks like I am losing connection of the red wire somewhere between where it connects to the fuse block and the connector itself that plugs into the blower module. I am going to slice the wire somewhere before the connector and see if maybe the connector is bad.

scrappy76

So I spliced the wire a few inches before the connector and tried it and still a no go. So I am losing power between the fuse block and the connector. The fsm manual shows nothing between the fuse and the connector. I could try another fuse for ***** and giggles. Whatcha think?

scrappy76

So does anyone ever heard of actually losing power between the fuse block and the module ?
is there something in between like a relay ?
Can I just run a new wire with a 30 amp inline fuse?

scrappy76

Yesterday I changed the 30 amp fuse to make sure it wasn't a faulty fuse, still no power at the connector. So according to the FSM, there is nothing between the fuse block and the connector. Next chance I get, I will take the battery out and look at the back of the fuse block and try and follow the wire up to the Connector to see what could be wrong. In the meantime, I ran a wire with an inline fuse in it from the fuse block terminal up to the blower module so I can run the fan for now. All is good. I will update when I get back to chasing the wire issue .