djcwardog

I recently got my factory air conditioning system up and running - thanks to Old Air Products. I had noticed that occasionally my fan would quit blowing and then work the next time I drove. If I jiggled connections down by the blower it would kick on. I found a ground wire plug that wanted to come apart just enough to disconnect. Solved that problem, now I get blower at all speeds except "high". Checking my trouble diagnosis charts (book: "Corvette Troubleshooting") only helps a little. With car off but ignition on and a/c set to "Max" to be sure that the compressor clutch engages (it does) I have tried: The resistor looks and tests good at all three posts for varying fan speed (stuck in the plenum near the a/c evaporator). When I unplug the two-wire connector down below that resistor I hear an audible click as the compressor clutch engages. There is a relay on the front of the evap box that takes a two-wire plug and single wires - orange and a black. I tested the orange wire for current and it was hot. Early in diagnosing the inop, I tried to jump that wire over to the motor and somehow must have blown its fuse - no longer hot. The problem is that I cannot find a blown fuse under the dash! The book mentions a 30-Amp inline fuse, but I cannot find it on my '73 car. This is aggravating! Apparently my motor is good and the fault lies with the circuitry. I would like to test the switch in the console, but need to get that orange wire to show current again. What do I need to do to get the blower working on "high"again? Once it works I may consider upgrading it to get more air volume. Suggestions for staying with the stock size fan and not having to go with a 1995 motor and spacer? Thanks!


[Modified by djcwardog, 6:04 AM 8/26/2003]

djcwardog

I just edited my post after I went back out to the garage and got the blower to work at all speeds except "high".... Help?

Thanks!

Smokehouse69

The 30 amp fuse is sort of hard to locate, since it is on the other side of the car from the blower. There should be an orange wire (12 gauge, I think) that is around the horn relay on the driverside fender-well, the fuse is a 30 amp glass tube type. It is common for these fuses to blow.

vettemack

He's right. Check the 30A fuse.

73jst4fun

The 30amp fuse is inline (orange wire) and connects to the horn relay just under the fender on the drivers side of the car. The orange wire 10/12 gauge wire is usually bundled with the vacuum lines. Strange they would run the connection all the way to the other side ....... :cheers:

Guru_4_hire

My heater fan doesnt work at all -- I am gonna run out and check it if I can find it.

Well I found it and inside is a 20amp fuse that is still good


[Modified by Guru_4_hire, 3:59 PM 8/26/2003]

Aflac

mine was only working on low and it was the blower relay...11$ at NAPA and it also helped with the cockpit heat... was getting a lot of heat in because (my theory here) i wasnt gwetting the gate in the heater system wasnt getting the signal to close... now when i turn the key on and cycle thru the different modes, i can audibly hear the gate opening and closing and my fan now works on all modes....i was getting worried about having to tear apart the dash to work over the gate

s79vette

on the firewall passenger side is your resister module. silver and bolted to
firewall near your heater wire plug. take it off and take it to Auto Zone
or comparable store and replace it with an exact replacement. I have a '79 and
I had to buy one for a 81 if I remember right. GM made a lot of different ones
to hook up to wiring and plugs aren't the same. This will cure your fan speed
problem, I learned it here, so bin ther dun that. Steve

TedH

There is also a rectifier that can be replaced in addition to the blower relay. Both are located on the firewall near the a/c box in the engine compartment of my car. I also found that the idle speed solenoid on the driver's side of the carb that increases idle with a/c on is also part of the circuit and must work.

Also, with the vacuum switch in the console that controls vent/fan/ac and heat, I had a vacuum leak; had to replace it to improve the vacuum signal.

I chased this one down about 3 years ago...

"The chain is only as good as its weakest link..."

djcwardog

First off, thanks everyone for the quick and very helpful replies! I found my 30A fuse under the left fender and the filler neck for the windshield washer bottle. It was blown - now replaced. I got my high speed back! Funny thing is that my blower speed is much stronger than before. I attribute this to a better ground path for the blower motor. I ran a new (longer) length of black ground wire when I saw that what existed was literally streched across the evaporator box. That tension would partially disconnect a black plastic connector for a single ground wire that runs to the blower case. Even with the tension off of that wire, I still get a partial disconnecting while out on the road. Obviously the stress deformed the connector over time. I plan to pull it apart this afternoon and spread the terminals just enough to assure positive contact. I can actually feel some cold air blowing on me at highway speeds. Not bad for a big-block car on these hot summer days.

Now if I could just get the steady-stae operating temperature down a bit. It runs at about 225-235 by the guage. I had the radiator rodded out and I just converted her back to a stock distributor with vacuum advance - selling my Mallory unilite YH with centrifugal advance. That is a great performance distributor, but not helpful for gas mileage. I'll take 15 mpg, but 7-9 mpg is a bit much for this old stock car.

Thanks again!