Fan Speed Switch

ed_in_pa · 03-15-04, 07:35 PM

I have a 1976 Corvette. I just got the heater working by replacing the heater control valve but I noticed the fan speed does't quite work right. At the far right high position it works, of course, on high. But it doesn't work on the other settings. I've only had this about a week and I'm just starting to fix minor problems. Any thoughts on what the problem is, could it be wired incorrectly or is it just a bad switch.

Thanks for any help.

03-15-04, 07:42 PM

Somewhere on the heater box.(and I am not sure where) there is a 3-4 wire connector connected to a resistor that goes into the heater box and into the air flow of the heater. This resistor, I suspect is burnt out!!! THATS MY GUESS!!! Good Luck!

80convertible · 03-15-04, 07:50 PM

Hi Ed,

I'm just North of you in the Allentown area. Going to get 3-6 inches of snow on Tuesday...not good vette driving weather. The first thing I would do is check the wiring and connections for that particular circuit. Remember how old your car really is. Over time connections become loose or corroded or the wiring or connector just age and fail. Several tools you really need are the assembly manual for 1976 and the 76 chevrolet service manual. You can pick up an assembly manual for around $20.00 new and a 76 chevrolet factory service manual on ebay for another $20.00 or so. The Haynes manual is also a good book for basic how to. And if you don't have one yet, an electical testing meter. Wiring is an ongoing project on an old vette. I've had my vette 5 years and always have to troubleshoot something electrical.

If your 76 wiring for the fan is anything like my 80, each speed of the fan has it's own wiring so the wiring for one speed can be functional while the wiring for any other speed (other than high in your case) could have failed or come loose for some reason. I've solved electrical problems by simply cleaning the connection due to corrosion. Amazing what you can do with a pencil eraser which works great for removing corrosion. Always start with the simplest and least expensive solution and work from there. That way you don't waste time and $$$$. Hopefully someone with a 76 can tell you where the fan/blower motor circuit is located for your year.

ScrantonScrambler · 03-15-04, 09:37 PM

Quote:

Originally Posted by ed_in_pa

I have a 1976 Corvette. I just got the heater working by replacing the heater control valve but I noticed the fan speed does't quite work right. At the far right high position it works, of course, on high. But it doesn't work on the other settings. I've only had this about a week and I'm just starting to fix minor problems. Any thoughts on what the problem is, could it be wired incorrectly or is it just a bad switch.

Thanks for any help.

check your relay & connections to it. Generally When these go bad the fan will work on high & no other speeds OR it will work on all speeds but high. The one shown in pic has a broken tang on the connector to prevent high from operating

ScrantonScrambler · 03-15-04, 09:59 PM

remove the relay & flip it over so you can see what you are doing. clip volt ohm meter on the tangs one at a time & listen for the tone while you operate the switch.

ed_in_pa · 03-16-04, 09:02 AM

Quote:

Originally Posted by ScrantonScrambler

remove the relay & flip it over so you can see what you are doing. clip volt ohm meter on the tangs one at a time & listen for the tone while you operate the switch.

thanks for all your replies, they are very helpful, I'll give them a try and let you know how I make out.