I can't see Paradise by the Dashboard Light

[Lowet50]

I apologize if this has been asked and answered. I am the proud owner of a new to me 1991 GT convertible. I have an issue with my "Instrument Panel Lights". My turn signals and all the warning indicators work fine but the Tach and Speedometer lights do not work. I already verified the fuse is good, replace a few of the bulbs, and installed a new dimmer switch. The problem persists, any ideas?

**UPDATE**
The plot thickens...The horn does not work, the park lights do not come on with the headlight switch, neither do the tail lights or license plate lights. I could replace the headlight switch but honestly at this point I believe it is a wiring issue, more specifically a broken ground somewhere.

 

[broncojunkie]

Have you tried testing some of these with a meter/light tester to see if power is going to them?

 

[ALMOST STOCK]

Ground locations.

 

[Lowet50]

I am currently out of town, I will test and report back next month.

 

[Lowet50]

I pulled every fuse out of the box and did a visual inspection, all "looked" good, no obvious blown or burnt areas. I had a mechanic that I trust look at everything and he discovered Fuse #4 was not only bad but the wrong amperage. He put the correct fuse in and that fixed everything except the horn. A previous owner replaced the steering column and cut all the wires, so no horn.

 

[Erkenbrand]

I pulled every fuse out of the box and did a visual inspection, all "looked" good, no obvious blown or burnt areas. I had a mechanic that I trust look at everything and he discovered Fuse #4 was not only bad but the wrong amperage. He put the correct fuse in and that fixed everything except the horn. A previous owner replaced the steering column and cut all the wires, so no horn.

I've been down that road. I couldn't get my brake lights to work for anything. Tried and tried. Every fuse looked great. Then, as a last step I just replaced every fuse in the box. Suddenly, working brake lights. Those blade fuses are so infuriating. I've taken to just testing each with my multimeter rather than trusting a visual inspection.

 

[ALMOST STOCK]

I pulled every fuse out of the box and did a visual inspection, all "looked" good, no obvious blown or burnt areas. I had a mechanic that I trust look at everything and he discovered Fuse #4 was not only bad but the wrong amperage. He put the correct fuse in and that fixed everything except the horn. A previous owner replaced the steering column and cut all the wires, so no horn.

Horn failure





Old horns like that work with an electromagnet and a set of contact points. The points are normally closed. When current flows the field from a coil of wire moves the diaphragm and the movement opens the points. When the points open the magnetic field dies and the diaphragm moves back; this keeps repeating.

When they sound like a dying duck and then finally die with a click, it is almost always because the "points" in the horn have gradually failed. This is very common.

There is always a small chance it is something else, but the safe bet on a failure like you had is to get at the horn.

Pull the driver side inner fender and do a good job. It is easier to take the wheel off and do it.

The relay has zero to do with common horn failures. They usually fail because water gets in the horn and sits there, with the moisture eating up the points. If you were mounted inside the fender between the grill and the wheel you'd be all messed up after a few weeks of wet weather and dusty road driving.

A relay failure is almost always an "it sounded perfect and suddenly quits" type of failure.

Horn Circuit

The horn circuit has a button that supplies ground, a relay that uses the button to switch the horns on and off, and two horns. The relay reduces the current that the horn button has to carry. This makes it possible to use a small and simple switch and slip ring on the steering wheel.

Note that the horn ground is built into the horn mount bracket, so the horn must be mounted on metal with a good connection to the car body.

 

[ALMOST STOCK]

I pulled every fuse out of the box and did a visual inspection, all "looked" good, no obvious blown or burnt areas. I had a mechanic that I trust look at everything and he discovered Fuse #4 was not only bad but the wrong amperage. He put the correct fuse in and that fixed everything except the horn. A previous owner replaced the steering column and cut all the wires, so no horn.