Having headlight switch issues.

[Carolina_Mountain_Mustangs]

I did a crash rush job getting the 73 vert back together to take to a show couple weeks ago and just getting back to getting a few bugs worked out.

When I turn the lights on the following work, headlights high and low beam, parking light, tail lights and back up, side marker lights, interior convience lights, center map light, shift indicator light, turn signals and turn signal indicator light in dash, brake light in dash, high beam light in dash and some of the lights behind the knobs on the dash.

Does not work.

None of the instrument cluster lights work, I tried turning the knob and nothing. I took switch out of dash and wiggled the wiring and still nothing. The clock light in console does not work. Brake lights do not come on when braking either. Will check connection on switch next.

The tach does not work either and I did install the tach adapter with the MSD ignition.

I pull the dash cluster and I had previously cleaned the circuit board and cleaned all the connections on the bulb bases and checked the bulbs but did again. I had another tach so I installed it. IS THERE A WAY TO TEST TACH OUTSIDE OF CAR?

So I went back to car with dash cluster out and turned on the lights and I have no power to the first to connectors on the plug that should be the common and + for the lights. When I bench test the instrument panel the lights come on so they are ok.

I do not see a fuse blown. WITH ALL THIS BEING SAID DO I ASSUME THE HEADLIGHT SWITCH OR THE REOSTATE IS BAD? I DO NOT HAVE A SPARE OUT OF A CAR TO SWAP AND DON'T WANT TO ORDER ONE AND NOT NEED IT EITHER.

Any suggestions on what to check?

BTW the seat belt buzzer, seat back releases and seat belt light on dash work.

I hate working on the electrical stuff cramped and I know nothing about it, lol.

Once I get this fixed I will venture out some and give it a shake down cruise. I have only driven about 15 miles.

I think the brake booster is shot very hard braking will do a vacuum check on it also.

If I need to order switch and get a booster what brands do I stay away from? I am sure they are all made off shore.

Thanks for any help.

 

[midlife]

Test for voltage at the smallest fuse (4 amps). Outside clip is incoming voltage from headlight switch; inside clip goes out to dash lamps. When probing for voltage, put probe on clip itself and not the fuse to determine if there is continuity between clip and fuse. If no voltage at outside clip, then the headlight switch is bad or a broken wire. If voltage there but not at inside clip, bad fuse or not enough tension on fuse by fuse clip. If voltage at inside clip but no lights, probably a broken wire or bad contact at the dash cluster connector to circuit card.

 

[Carolina_Mountain_Mustangs]

Thanks for the tips from someone that knows what they are doing, lol. Will check it out tomorrow. Good thing is I have the two post lift and I raise the car up and stand beside it to work and don't have to try to lay in the car.

If a bad switch who is best to buy, Brand?

 

[Carolina_Mountain_Mustangs]

A little update on this battle with the electrical gremlins.

I put a new headlight switch on Sunday and still no dash lights, lol.

I took the cluster back out and I had another tach cluster so I took the circuit board off it and cleaned all connections with fine steel wool and put on the cluster. All six dash lights work. I tested all the other circuits and they all work.

When I probe the small fuse in the fuse box I have voltage on the terminals along with the fuse and the rheostat on the switch does run voltage up and down.

I probe the dash connection and the first terminal has power and the second checks out to be grounded. I put the cluster back in no lights. I take it out probe again and test lights again and everything works.

What can be breaking the circuit when I plug in the cluster?

Got the brake lights working was just how the switch was turned.

Another strange thing on this car. I cannot no way plug the speedometer into the cluster way too short. Was there not something added to the 73 like an extension or something different on 73? I am going over to my other 73 this afternoon and start robbing parts.

Thanks for an help or experience on this happening. Running me crazy. Works out of the car but not in everything checks good with voltage and ground in car but does not work.

 

[73pony]

On the speedo cable. It is a PITA. I figured out two ways to do it.

1. removed the dash pad etc and try to reach down in from the top to connect it. Not easy but can be done.

2. easier in the long run. disconnect the speedo cable from the trans and back feed it up into the dash to give you enough room to get it connected. Then have someone gently guide it back out the firewall while you put the cluster back in and reconnect at trans.

 

[jeff8877]

On the speedo cable. It is a PITA. I figured out two ways to do it.

1. removed the dash pad etc and try to reach down in from the top to connect it. Not easy but can be done.

2. easier in the long run. disconnect the speedo cable from the trans and back feed it up into the dash to give you enough room to get it connected. Then have someone gently guide it back out the firewall while you put the cluster back in and reconnect at trans.

On the speedo cable...there is a clip that holds that plastic cover to the bottom of the car. If you loosen the clip and let the cable out it gives you a little more room which made the difference for me.

 

[midlife]

Regarding dash lamps: on a tach dash, pin 11 is black (ground) and pin 12 (blue/red) is dash lamps. Sounds like the dash cluster pins are simply not making good contact with the circuit card.

Gee...how many times have I heard this story? And you wonder why I decided to manufacture a hard-wired dash cluster harness to get rid of that damn circuit card?

 

[Carolina_Mountain_Mustangs]

After it got dark I figured it out. It is too light in the garage they were working and probably have been just could not see them.

Now down to getting the tach to work when I fired the car nothing and I swapped it out with a known working tach. Somehow I ended up with 6 cars with gauges and tach and one spare. I am sure it is something with how I hooked up the MSD but I went by their directions for a Ford tach and installed the adapter. As usual I will go back to ground zero and start over probably did something stupid. It sucks getting old and gas is getting expensive, lol.

On the speedo I know they cut the cable short I have 6 of these cars and this is the only one that is this way like 2" short. The PO had it unhooked when I got.

He did go from a 'FMX to a C6 do they use different cables? That is what I am thinking is wrong. I have for C-6, 4 speed, 3 speed and another FMX but I do not have another car with a C-4 so I cannot compare. I am sure someone has done that swap and will know.