Swapped under dash harness, car won't start

Hi all, after what seemed like lot’s of electrical problems: initially signals not working, dash not working, heater core, etc. I decided to start fresh and get a refurbished under dash harness from WCCC. It took me a number of hours to get the old one out and label every contact as I did so. I then transferred these labels to the new harness. I finished connecting everything yesterday and now the car won’t start. As most stuff is lighting up, I’m guessing it’s a problem with the ignition switch.

There seemed to be a broken piece of plastic when I removed it from the old and transferred to the new. Any thoughts on how I can trouble shoot? It seems odd that it turned over just fine before swapping and now it doesn’t.

When you say the car doesn’t start, does that mean it doesn’t crank or it cranks but doesn’t catch? Big difference there for trouble-shooting.
What year is your car?
Is the car an automagic tranny version? Check the neutral safety switch/backup light plug and the NSS itself for alignment.
Is the car a tach car? Is the tach plugged in so that the signal from ignition to coil is complete?

First I’d check for power to the coil + post with the key on engine off. Then disconnect the lead from the starter solenoid and check for power with the key in the start position. I’m using this as a test for my '67 since I don’t know the year of your car.

I should have posted earlier. Shortly after posting I realized that I broke part of the plastic on the ignition switch. I ordered a new one from Summit racing and it started right up. Thank you for the quick responses.

Glad to hear you got it fixed.

Well it worked last weekend. Now it won’t turn the crank over. I turn it all the way over and I don’t hear anything. It’s a 1967 standard automatic.

Neutral safety switch?

After knocking the starter relay and jiggling the wires I got it to start. I later changed the starter relay and got the car to start but it sounded like complete dog shit. Lot’s of weird noises and rumblings and then the car wouldn’t shut off when I took the key out. I had to pull the coil to kill the car. I’ve since changed the starter and got a new battery. I thought everything was fixed and then it’s done this two more times but not every time I start the car. Any ideas on what could be causing all the weird squealing noises and is preventing me from turning the car off?

Starter solenoid

Get one from Ford. Auto parts store starter relays are junk.

There is a reproduction of the original Autolite Starter relay (aka solenoid) sold by most of the Cougar part vendors. It is notorious for doing exactly what you say yours did.

I agree with those who said to get the new Motorcraft solenoid. Well made, doesn’t fail.

Awesome, thanks for the help. I had never had the problem until purchasing the new starter relay at O’reilly’s. Can you please direct me to a link or give a part number I should purchase for a better one?

The other issue is, my dash lights still seem dim and are flickering. Do I now need to replace the under hood dash harness or are their other things I can check or look at?

Dash lights have nothing to do with the under hood harness excepting main power distribution to the ignition and headlight switch, which is where dash lamp voltage originates. From there, it goes to a variable resistor (the headlight switch knob) to control brightness, then to the fuse box, and then to the dash lamps. Flickering dash lamps means either a bat rheostat (headlight switch) or bad contacts at the fuse box.

Any Ford dealer has it under Motorcraft #7663. I would not give 25 cents for the one O’Reilly’s sells.

O’Reilly’s also sells the Motorcraft unit, if that’s more convenient to you.


Midlife, thanks for educating me on the electrical loop for the lights. Before changing the under the dash harness I put in a new variable switch knob and before putting the harness in, I soldered in new fuse contacts. Is there something I’m missing?

Thanks you Royce and PacificaXR7GT, I’ll look into purchasing a new one.

Just because a variable switch is new doesn’t mean it is good. How good is your soldering? Turn switch as far on as you can and measure voltage at the fuse leads and report back.
It could also be a bad ground on the dash, but your gauges would also flicker.

Midlife, the soldering is perfect. I had our 20yr electrical tech do it. The dashes are flickering as well. So maybe it is a grounding issue. Is it just the two grounding points, one behind the dash and one near the glove box? Also, where would you suggest probing? The 14v fuse contacts for the dash?

Yes, although the 2.5 or 4 amp fuse (depending upon year) clips in the fusebox. They should read the same, but not battery voltage as it is reduced by the rheostat (variable resistor) in the headlight switch.
Check your constant voltage regulator on the back of the dash cluster and make sure it is properly grounded to the case or circuit card (depends upon year). A regular flickering suggests some sort of feedback from the CVR or a circuit breaker or a turn signal switch flasher can.

There are multiple places where the ground connection can cause this sort of trouble. Coming to mind are the voltage regulator to radiator core support, alternator and battery ground wires (same bolt) to the engine block, and the ground for the instrument cluster to the body. The starter relay (solenoid) also needs to ground to the fender apron to work.