Question: Why Won't My New Blower Switch Work?

[yello80vette]

In my 1980, the heat/AC blower fan switch has not worked on 'high' since I got the car a few years ago. (It has worked on low and medium).
Well, I finally got around to getting a new switch. However, when I put this one in it doesn't work at all. I tried putting the old switch back in to see if it would at least work on the two settings it did before. Nope. That one doesn't work at all either now. You can hear the blower running when you listen to it under the hood and when you turn it on with the new switch, you can hear the relay click. Anybody have any idea what could be causing something weird like this? This one's got me stumped!

 

[damoroso]

It's likely a loose wire in a connector that's keeping the switch from working at all, make sure the connector is on the switch straight. Also, sometimes these wires back out of the connector just enough not to make contact. Check that too. If that's all good, then I'd check the resistor (it's on top of the air box with a 4(?) wire plug on it and two screws that hold it in place), or the relay, mounted on the firewall above the air box, with heavy wires pluging in from the bottom. You can pull the resistor out and see if anything is wrong. If you don't see anything, try the relay. Again, make sure those wires are in the connector all the way.

 

[bill81vette]

Check the fuse as well ...
I had one the INSIDE of the fuse corroded,never noticed it.drove me nuts trying to find out why the blower would not work correctly!!!!

 

[6880 Mike]

...Check the fuse as well ...

 

[yello80vette]

The first thing I did was check the fuses. As a matter of fact, I checked every one in the entire fuse box, just in case. They all looked fine but I went ahead and changed every fuse with a new one.
I was getting NO power to the blower before and in doing this, I at least got power to it.
Even though I did a close visual inspection on every fuse, apparently one was bad after all. That just shows how delicate these fuses can be.

Now I've just got to figure out the switch problem. Thanks.

 

[TimAT]

You have no control of the blower? Or just no HI? OR just nothing else?
No HI, likely cause is either the relay OR the power to it. The HI blow relay is mounted on the firewall, just inboard from the heater fan motor.
If no other speeds, the resistor is IN the heater case with about 5 wires on a connector.

 

[yello80vette]

Before, the switch did work on low and medium but not on high. I thought it was a bad switch, so I got a new one. I put this one in and it doesn't work at all. I stuck the old switch back in to see what happened and now it doesn't work at all either.

 

[TimAT]

The best way I know of to track this down is with a wiring diagram. Here's a link":

http://www.nrjvette.com/johdotukset/Chevy Corvette 1980.pdf

Print it, then take a hi-lighter and color all the wires in the heater blower system. I'd use a couple different colors- one for power, one for control, and maybe a black marker for the grounds. It may make it easier to see if you place the pages (may take more than just a single page) and tape them together so the circuits and wire numbers line up page-to-page.

I've done this chasing wiring prints on airplanes chasing a problem. End up with a desk covered with a collection of prints, but it shows ALL the connections to a component.

Hang in there. :confusedNotice on the print- and the diagram is not real clear- wire 101 in the relay (Dk Blue) runs from the relay to the resistor- that is the one that powers the blower thru the resistor for all speeds except HI. When it's switched to HI, the relay shifts power from 101 to 2. All power to the blower motor runs thru 65 (PPL). Ckt 2 (RED) is fed from a splice in one of the fusible links.
At the fan switch, power comes in on 52 (ORG/Orange) and is fed back out via 63,72,50 to the resistor.

Hope this helps. Let us know.

 

[yello80vette]

This took you a lot of time. I can't say how much I appreciate it. The wiring diagram is excellent. I'll post when I get the results. Thanks for the help. -d-

 

[TimAT]

No problem- Imagine chasing all the wires thru a plug with 80 or 90 wires going into it. These cars are easy-

 

[yello80vette]

Here's something I've found that seems odd. It makes me think there could be a short somewhere. When the ignition is on, I can hear the blower motor running on low. This happens if the blower switch is plugged into the connection or not, and if the switch is connected, it doesn't have to even be on. However, if I hold the blower switch between the off and low settings, the fan goes off. Does this mean anything significant to you? Again, thanks for all the help.

 

[TimAT]

GM had to make the blower run low all the time to satisfy Ralph Nader. That's normal.

Have you got a 12v testlight? Makes chasing electrical problems a snap.

 

[yello80vette]

Well, I don't really understand the reasoning for that, unless it's to make it easier for Nader to stay full of hot air. Thanks for all your help. -damian-

 

[TimAT]

With air constantly circulating, no chance for carbon monoxide to build up in the interior.

 

[wishuwerehere82]

The fan speed switch is connected to a resistor array that is inside a silver module mounted on the firewall. The resistors determine the fan speed based on thier resistance. It's a plug-in module that looks very much like a relay. Inside the silver module are wires of different resistance that connect ot a common terminal that goes to the blower motor.
A bad connector to the module or burned out resistor inside the module is probably the cause of it working at lower speeds but not full speed.
The high speed resistor isn't really a resistor, but a straight-through path to the motor. Thus, it carries the highest amount of current and tends to burn the connector faster than the other two.

 

[Koop]

My car is much older than yours, but I'd be lookin' at the relay.

 

[Checklst]

Koop is right look at the relay and its connector........a vary large % of blower troubles are the relay.

Do not assume it is bad a buy a new one.......just remove the case on the relay .......hook up a continuity light and test the magnet coil.....most are still good, if so just clean the contact post and points with a flat file and bend the (spring metal of the points) a little closer to the copper post.

She will work like new after that. Most time it corrosion/rust in the electrical connector..........a small file and electronic contact cleaner will make them work like new.

 

[bikemiser]

Ok thanks but the high speed works, thats why I think it is the resistors.