1965 Ford Mustang Under Dash Electrical Repair, And 3 Speed Heater Switch Upgrade – San Diego, California

     A customer just had his 1965 Ford Mustang dash painted, but most of his dash electrical did not work after he got it back. I asked if his main under dash wiring harness was original, so I know what to expect. Most of the original wiring harnesses that I’ve seen have been through 40 plus years of repair abuse. Everything from bare twisted wires with barely a piece of electrical tape, to home electrical twist connectors. His harness was new, but I was surprised at what I had found.

     The heater, windshield wipers and radio were not working. Also, some of his instrument gauge lighting were not working. I removed his aftermarket instrument gauges to get a better look, but I could not see passed the web of extra wiring. The first thing I decided to do was to clean up the instrument gauge wiring. Original 65-66 Mustang gauges have short wires, so you can’t move them far without disconnecting the individual plugs. Since these were aftermarket, I lengthen the wires, so you can have the gauges sitting on top of the dash pad without disconnecting them. Afterwards, I was able to check all the switches, and plugs. None of the dash switches had power, so I checked the fuse panels. There was no power going into the fuse box. I then checked the back of ignition switch to see if the body shop re-installed the main dash power wire. The loop connector was on tight, but the wire was pulled out. Mystery solved!

     The new main under dash electrical was upgraded to a GT style harness with a 3 speed heater motor. The original 2 speed heater switch was used, but had been wired to work with the heater motor. I installed the correct heater switch. The 3 speed switches plug into the front of the heater boxes, so I installed a stock heater resistor in the correct location. Now the 3 speed heater motor works on all speeds.

If you’re having electical issues on your Classic Mustang, then give Classic Resto Garage a call at a 619-929-8506, or fill the contact form.

Happy Cruising!

posted by inlinesix in 65-66 Mustang and have No Comments