VettemanVan

Hi Everyone,
I've owned this 1970 Corvette for 3 years now and the fan/blower motor has never worked. It is a factory A/C car and the compressor is still connected but no belt.
Recently I started trying to get the fan/blower motor working but have had no luck. Parts I have replaced: new blower motor, new high speed relay, new resister, tried two new fan switches, checked and reworked grounds, still not working. The main A/C fuse under the dash is fine. (I pulled the fuse and cleaned the fuse block good with sandpaper.) I also checked the in-line fuse under the driver's side fender when I replaced the horn relay recently and it is also fine.
I know the wiper motor shares a ground with the blower motor and I added an additional ground for that as well and installed a separate ground wire from the actual new blower motor to the frame of the car. Windshield wipers work great so don't think it is a ground issue. I ran a wire from my battery straight to the new fan motor to make sure it wasn't defective and it works fine running it that way.

I replaced the fan switch last week and it didn't correct the problem. With the ignition on, I could put the fan speed lever on HIGH and if I wiggled it a bit, the fan would eventually come on and run but ONLY on high speed. When I wiggle the lever again or drop lever down to the lower speeds, the fan just quits completely. While it is running, I can roll my controller wheel up to OFF and it will shut off.
I assumed the fan blower switch was bad and had the Corvette parts supplier send me another one, only to have the same identical problem. I ordered a wiring diagram that came today and it has helped me to understand the wire routing but still no success.
I read someone's similar problem on another thread and today I tried the trouble-shooting ideas that were suggested but still no success. That person has a '74 and his high speed fan wouldn't work at all (different than my problem) but I just tried some of the trouble-shooting ideas to learn what I should see when checking voltages on the relay and switch under different fan speeds in hopes of getting ideas of issues to look for.

Here is what I get...when I put the fan selector on high, I ONLY get 12 volts on the Orange wire at the relay. As a matter of fact, the Orange wire is the only wire that shows voltage when any speed is selected at the fan switch. (Also, No voltage to the Dark Blue or Purple wire at relay at any fan speed.) I can drop selector down to medium or low speed and same thing...fan won't run and NO voltage at relay EXCEPT on the Orange wire.
Inside the car, I understand the Dark Blue wire on the fan switch should show voltage when the selector is on high but mine shows no voltage.

There is a black 2 prong connector that connects to the controller at the left rear corner of the controller and I assume that plug is what powers up the controller.
On this 2 prong connector, there is a dark brown wire on one spade and the other spade has a light brown wire and a green wire. The dark brown connector spade shows 12 volts and is hot all the time. The other spade with the light brown & green wire shows no voltage.
There are 3 other connectors that plug in to different spades under the controller and when my "wheel" is moved out of OFF to A/C, Heat, or any other position, these other connectors all receive 12 volts on one spade. When the controller wheel is rolled back to OFF, these 3 other connectors (behind the 2 prong power supply connector) no longer show voltage. The power supply 2 prong connector at the back left continues to show 12 volts.
So.....my controller is getting 12 volts but it appears the voltage may not be going where it should. I pulled the controller out while I was checking the condition of the connector terminals and I installed the wiring and connectors exactly as they were. There is evidence that someone has had been in there before because the orange wire for the cigarette lighter was unplugged.
Sorry for the long post but ready to pull my hair out. Could I have possibly received two bad fan switches...? Anybody got any ideas they would kindly share...? Thanks in advance!

Peterbuilt

bobby70

Out side on fire wall there is a black ground wire that should be attached to the wiper motor and many people call it a live ground wire check your wire harness out that is where you get power to the low and med too the fan won my 70 ac car I took out the fan and put in a 1992 corvette fan in and it. is night and day the only thing you have to make is a spacer in-between the fan and fire wall about 1-1/2 in wide plus a new connter to fit on the new fan and check the 2 black wires that turn into 1 that connects to the. fan let me know how you make out they sell the new wire connector on eBay

bobby70

HE said he had a 70 complete deferent than a 78-82

VettemanVan

Hi Peterbuilt,
Yes - this gives me a lot more info on how to understand the relationship between the switch, relay and the resister. I will print this tomorrow and take it into my shop and see if I can use it to resolve my issue. I bought a 11 x 17 color wiring diagram for my '70 Vette and it came today. It was helpful but I was still confused on the connections at the fan switch and how they coincided with the relay. This will help so hopefully I can use this to help figure it out.
You guys are great - thanks so much!!
Van

VettemanVan

Hey Bobby,
Thanks so much for this info! I've read about the black ground wire attached to the wiper motor but didn't find it. I probably need to pull the plastic cover off to see it and I will do that tomorrow. Wasn't really thinking I had a ground problem since my wipers work great but I do know the grounds for the wiper motor and blower motor are tied together. I will definitely look for that ground though, especially if that is where the power for low and medium speeds come from.
I will let you know if I find it and figure it out.
Thanks Bobby!!
Van

Eliredandblack

Simply try a temporary ground and you will know immediately if that is your real problem. I had trouble on my 73 with factory air, and I bought a new relay that is mounted on the heater box under the hood, no it didn’t fix the no fan running problem. After speeding more time than I will admit, the problem was with the 50 year old plastic plug going to the relay. One of the brass terminals was not making contact because the plastic on the plug was deteriorated. Ensure that all terminals on the plug are tight and there is no corrosion.

Blue73Shark

I just had this EXACT same problem on my 73. Cleaned and tightened the ground plug that attached to the relay and it now works perfectly.

Fran

VettemanVan

Hi - thanks so much for the suggestion. I actually replaced the 3 prong terminal connector ends at the relay as well as the connector terminal for the ground spade. I too thought that was the problem but unfortunately, it did not help. I watched a video with a guy that is really good at troubleshooting Vettes (Problem Solver Garage) and he demonstrated putting a set of jumper cables from the wiper motor housing to a good ground. It worked on his Vette but didn't help my situation so I'm not sure if I have a grounding issue or not. I actually ran a separate additional ground wire from the new blower motor to a clean spot on the frame and still nothing.
The search continues... THANKS AGAIN!!

VettemanVan

Hi Blue73Shark - I replaced the ground terminal connector for the relay but since you had the exact same issue, I'm going to double-check and make sure it does have a good and tight connection. Thanks so much!

Van

VettemanVan

Hey Bobby - I just took a closer look at the wiper motor and discovered a small black wire at around the 11:00 position on the wiper motor screws that someone has cut. Is this the original ground wire that you are talking about...? Why someone would have cut it, I don't know. If that's it, where all does this black wire supposed to go?
I've read that the wiper ground was originally used for the blower motor ground too. If this is it, I want to run it back like it is supposed to be as this could be my problem. I've run a separate ground from the blower motor to the frame but maybe it also grounds other necessary stuff to make the blower/fan motor work correctly.
Thanks again!
Van

Blue73Shark

I only found the soulution by wiggeling the ground connector as it looked perfectly fine installed on the relay spade. I wanted to simulate engine vibration and sure enough, that revealed the problem.

Fran

kansas123

I had some similar problems with my blower motor not running and found it was due to that two wires that turns into one. I grounded it to one of the bolts that hold the compressor on. Problem solved. Hope you get yours going.

VettemanVan

Hi Kansas,
Are you talking about the two ground wires (Brown &Black wires) that join and become one and attach to the blower motor around the 1:00 position...? If that is what you're talking about, I actually replaced the one connector today with a new connector (where they join together as one) and reattached it to the same position on the blower motor housing. I will certainly try to do the same and see if it helps me too.

Thanks so much!
Van

VettemanVan

I actually replaced that ground connector today with a new one that had a tight fit but unfortunately it didn't help. Today I replaced any connector that was questionable on the relay and the blower motor grounds but none of that changed anything. Looking at the positive side...I'll definitely have good connections though.
Thanks again for the idea and suggestion!

Van

bobby70

bobby70

I have more pix if you need more ,if. there is a part you need I might have it.bob

bobby70

that black wire is part of the ground wire. for the fan, there is a metal spade on the washer pump down around 7:00

67:72

It's been a little hard to follow all of the suggestions and replies in this thread, so forgive me if I'm repeating something already said.

(BTW, having a '70-'72 is fantastic when dealing with the blower motor -- much easier to reach, see, and R&R the motor by removing the side grate.)

The grounds for both the blower and the wiper motor are simple L-shaped spades that go under one of the small bolts surrounding their respective housings.

VettemanVan

Wow - thanks for all the helpful pics, Bob! I like what you've done with yours!
I've actually been in the shop working on it most of the day and somehow the blower motor is working now. I found the correct ground spade on the windshield wiper motor and the original ground was actually still hooked up there. As a last ditch effort, I reinstalled the old original blower/fan switch and believe it or not, the damn thing started working! Not sure why or how.
I bought and installed the new fan/blower switch, relay, resistor, and replaced some of the terminal connectors and "tightened" up some of the connections and the motor still wouldn't run, except on high speed (but only when I jiggled the speed selector). This afternoon I was about ready to give up as I had done all I could do and decided to see if the original fan switch would react the same way. I hooked it up and it actually worked correctly. I guess neither of the two blower/fan switches I bought from the Corvette supplier last week were any good because even after the troubleshooting I did today, it wouldn't work until I installed the old original switch. Anyway, just thankful it is working and I appreciate everybody's help and suggestions!!

BUT NOW...after all that, the damn windshield wiper door won't open when I press the wiper button. It was working fine before I started working on the fan motor & switch. If I pull my vacuum button that's at my knees, the wiper door will then open (with vacuum) and THEN I can press the wiper button and the wipers will work.
I didn't unplug anything with the wipers or vacuum lines so not sure why I started having this issue all of a sudden. I just read a couple of things to check out regarding this wiper issue since I walked in the house an hour ago so guess I can look at a few possible culprits tomorrow.
Thanks again Bob!!