Classic/Antique Car Repair: 1966 Mustang & Holley Carb, amp fuse, holley 80457

Question
Hi Dick,
I recently put a Holley 80457-0 on my 66 Mustang. The carb has a wire that needs 12V which is hot anytime the key is on. I have run a wire to the wiper motor (as suggested by Holley), but I cannot seem to find the 12V wiper motor wire using a voltmeter when the key is on. The wiper motor has 4 wires, and two of them register on the voltmeter when the wipers are on, but none of the 4 wires register anything when the key is on and the wipers are off. I have the positive voltmeter spike on the wire and the negative spike on metal to ground it. I could run the wire to the fusebox but I am unsure which fuse to run it into. Holley said to use a 14 gauge wire (which I have) and a 10 amp fuse. None of the fuses currently in the car are 10 amps.

I hope this is enough information for you to make some suggestions. I have been told by Holley the 12V wire hookup is a must for normal carb operation. Basically the motor is idling too fast - I have tried adjusting the idle speed screw with no luck. Thanks in Advance, Rick

Answer
Thanks for a crystal clear explanation of what you are doing.  The wire that requires 12 volts to the carburetor is the automatic choke heater.  Running the car with the wire disconnected is causing the engine to run on fast idle continuously, because the choke is staying on. You must solve this problem, and then re-adjust your curb (warm) idle to the original setting.

You are using the voltmeter correctly.  The size of the fuse should have been specified as the minimum acceptable rating - it is OK to use a 15 amp fuse also, if that is what is supplying the wiper motor.  

Since you know the wiper blades park themselves when you turn off the wipers with the key on, you can be certain there is one wire to the wiper motor which has 12 volts whenever the key is on, regardless of whether the wipers are on or not - I cannot understand why you didn't find that wire, since you are doing everything correctly.  I'd suggest you try again, checking every wire that goes to the wiper motor.  I think you know this, but the ignition key must be "ON" and the wipers turned off.

If you absolutely cannot find the right wire on the wiper motor, you can also use the "I" terminal on the ignition switch to provide the 12 volts. It comes on and goes off at the proper times for correct   operation of the carburetor.

Dick

There should be one wire to the wiper motor