Hello All,

This is my first time posting so please forgive me if I don't do this right. I've been reading the post on here for a long time and have found you guys are the most knowledgeable people around so I figured I would give this a try. I have a 1964 corvette and I cannot get the heater to work I consider myself rather good at fixing things on cars and have been a body man all my life, but I'm at my wits end on this. every time I put a fuse in the fuse box and turn the key on the fuse blows. I have ran power straight to the fan motor and it works fine. There is no power going to the fan from the fuse box itself. I also replaced the resistor in the fan tunnel the one that tells the switch how hot the air is. When I bought the car nothing in the interior worked and now I have every thing working except the heater. ANY help you guys could give me would be wonderful. I purchased all the shop manuals but i'm not real good with the electrical stuff. Please no rude or bad comments I'm just a guy trying to fix my heater. Thanks to you all even if you do not help I love to read about you problems Thanks, Rick Utah

 

You've already checked out the fan motor, so it's out of the list of possible troubles. It would be a good idea to find a wiring diagram (they're available from at least one source on this forum; just search) so you can trace all the circuit elements and locate what seems to be a short circuit to ground somewhere.

There are a couple of things you can do without a wiring diagram to eliminate some possible faults in the meantime. You will need a multitester or a test light for these tests:

1) Pull the left hand harness connector off at the firewall. Look for the same color wire at the connector as the power wire to the fan motor (it's orange on a '66, not sure about '64). Check the wire for continuity and whether it's insulated from ground.

2) Pull the connector off the fan speed switch. With the fuse that blows out of the box, check each wire for insulation and continuity. One of them is the power wire to the fuse box. It's orange on a '66; not sure about '64. That one should show zero ohms or light up the test light between the switch connector and the "cold" terminal in the fuse box. The other wires route through the resistor and one routes to the corresponding terminal on the firewall plug that you checked in item (1). If any of those wires show a short to ground the problem is in your dash harness.

Hope this helps.

 

Assuming that you have the stock fan circuit

There's no resistor that senses temperature, so I am also assuming that you are talking about the resistor that drops the 12v to lower voltages to run the fan at lower speeds (low, med). I will attach a wiring diagram below of a 65, but I believe it is the same. After the orange wire goes through the firewall connector, it connects through a noise suppression capacitor to the hot lug on the fan. That capacitor could be shorted, but if you disconnect that orange wire before the capacitor and the fuse still blows, it's before that. The most likely short would be in the wiring of the fan speed resistor circuit or fan switch. Notice that there is no ground at the fan switch or resistor. The only ground is on the black wire on the other side of the fan motor, so you should not read to ground on any of those wires with the orange to the fan disconnected. Disconnect the right hand firewall connector and read on the brown wire from the fuse to the fan switch (or on the right side of the fuse) and it should read open circuit Take a look at the diagram and see if it leads you to anything. One other thought, are you using a 10 amp fuse? If you have a smaller fuse, it may be blowing due to the current drawn to start the fan. The voltage to run the fan comes from the fan speed resistor, which is fed by the brown wire from the fuse box.
The only things that should be wired in the circuit are the fan switch, fan resistor, noise suppression capacitor, and the fan motor.

 

Rick - Welcome to the Corvette Forum. You've gotten good advice above since it sounds like your problem is with the blower motor. Question for you, when you're driving and activate the heater, even with no blower motor working can you feel warm air coming out the vents? Does your 64 have A/C? I believe only the A/C cars had a shutoff valve in the supply hose between the engine and the heater core. The non-A/C cars did not and only used dampers in the heater box as a way to stop hot air from entering the passenger compartment. If you can still feel warm air coming from the heater, then the core is still functioning correctly.
Mike T - Prescott AZ

 

Any progress?

 

Hello all,

I can't thank all of you who replied for the wealth of knowledge you supplied me with. I will be working on that heater tomorrow and I'm sure with the information you guys gave me I will be able to figure it out. I hope. I will keep you guys informed of my progress but I didn't want anyone thinking I was ignoring them after they helped me out so much. I promise you will here from me again. You guys truly are my hero's and thank you for your information and concern. Oh and to the one who asked me about A/C that's a no I could only wish. Rick in Utah

 

Ok left or right as I'm siting in the car. The right side of fuse shows an open circuit. The left side of the fuse shows 11.92 volts. under the hood at the right plug I unplugged it and there's no power except the top lug. At the fan there's no power but plenty of ground. The fan works if I run direct power to it. At that resistor in the heater tunnel that tells the switch what to do there's nothing either. Any Help or am I even doing this right?

 

That just means the fuse is blown. If you're using a 10a fuse, you have to find what is shorted. Can you disconnect the power wire going to the heater BEFORE the noise suppression capacitor? If you disconnect that wire and measure with an OHMETER, not voltmeter on the right side of the fuse, are you getting a short to ground? It should read open (infinity) to ground with the orange wire off the heater fan. If it does, your capacitor must be shorted. You can remove it and connect the power wire directly to the fan, the only negative consequence is that you MAY get static in the am radio when you run the fan. The capacitor isn't necessary to operate the fan. If it reads low ohms on the right side of the fuse with the orange wire disconnected, you have a short in the wiring between the fuse and the fan switch or resistor somewhere. Double check the wiring on the fan switch, there should be no ground there anywhere.