Speedometer lights not working now

[Soylent]

I know that this may end up with me tracing wires with a multimeter but hoping for something simple I have missed.

It was time to replace my speedometer as the my mph needle was doing 360s and the headunit mounts were broken. All the lights and gauges were working.

I purchased a new cluster from Tom’s with a voltmeter. Had pictures of the original before removing and labeled all wires. Installed the new cluster, reconnected the wires. New 12 volt jumper to + on voltmeter, grounded voltmeter to speedo case, and added another ground from speedometer to dash. Replaced old bulbs with leds from Tom’s. All gauges work but no lights and no signals. Pulled a led and added oem bulb. Didn’t light. Checked the post in the socket and no voltage. Tried the brights and the bulb lit for a second. Found aga-2 fuse blown. Replaced it and looks like it blew again.

What could have changed with a simple remove and replace? LEDs are supposed to be low draw right? Ordered more 2 amps fuses and oem bulbs.

 

[DirtDonk]

At first, I was gonna say, make sure that the rheostat on the headlight switch is turned up all the way. Then pull the headlight switch out one notch.
But as soon as you said it’s blowing the fuse, sounds like there’s either a short circuit in one of the wires, or in the headlight switch itself.
Is it a new headlight switch?

 

[Soylent]

No it’s original and I can’t turn it to accessory anymore (or ever). Reason to order a new one. Maybe when I was pulling the harness a little to get the speedo out I pulled something loose on the ign switch?

 

[DirtDonk]

The ignition switch doesn’t control the light circuit at all. If the small two amp fuse is blowing, it’s strictly between the headlight switch, the fuse, and the instrument/dash lights.
Is that the fuse that’s blowing? The smallest one?
It’s the only one that’s not either powered all the time, or through the ignition switch. Just the light switch. Which has its own protection for the main functions.
There’s an internal circuit breaker for all of that. Only the dash lights are protected by the fuse.

 

[Soylent]

Yes it’s the short 2 amp fuse. The dimming function of it didn’t work well before the change. Sometimes it was either on or off. I have ordered a new one. Hoping it is that and not a wire burried in the harness. I’ve noticed that the fuse clips in the fuse box have a little of white corrosion so will sand those off as well.

 

[DirtDonk]

Yes, a good idea with the old glass fuses to at least once every year or two, pull all the fuses and clean the contacts.
A layer of oxidation builds up and impedes the flow of electricity. And hopefully you can get to them before they actually start to rust.
When they built up a layer of true surface rust everywhere, it’s time to go to Plan B.
If it’s just rusty on the ends, but the actual clamp part that goes around the fuse body is still clean, then they are still workable.
At that point, you have to look behind and see how crusty it is in the back where the wires are.
Sometimes a wire brush will clean off the cobwebs, dust, and rust for a little extended life of an old component.
Just make sure you disconnect the battery before you work on the backside with a wire brush.

If the dimming function didn’t work before, it sure as heck is not gonna work with LED bulbs.
In fact, unless both the switch and bulbs are compatible, LEDs, don’t dim noticeably. You might get a flicker and you might find a position where they are in fact dimmer. But that’s just luck and usually you don’t get dimming with LEDs.
Sometimes even “dimmable“ LEDs won’t dim properly with an old switch.
Unfortunately, your switch sounds like it’s past it. Your only alternative is to fix it yourself, which I don’t think I’ve ever seen anybody do here in a long time, or buy a new one.
And that’s a crapshoot. So let’s hope the blowing fuse is a result of the old light switch, and that the new one fixes it.

 

[Jdgephar]

try reversing the polarity on the LEDs. They only work one way. Old school bulbs don't care which way the current flows.


Edit....sorry, that won't blow the fuse. It would just not light up. You've got something direct to ground that shouldn't be.

 

[Soylent]

Hoping it is the switch too. Will probably pull the fuse box and give a good cleaning. Switches, bulbs, and fuses are inbound. There are also a bunch of wire taps from po that hopefully aren’t causing issues. Will have to check which wires they are tapped into.