jgcalifornia

I replace the fuse and it just blows again, at no particular time. I replace it to check my gas & temp levels, but usually within 5 minutes it goes again.

This fuse controls the gas gauge, temp gauge and heater blower.

Any ideas on what is causing it to blow?

2ToyGuy

Can you tell us the name of the fuse that's blowing? That might help us trace out the circuit(s) that use it, and see what's possibly happening. Like IGN, ENG, TAIL, etc, as examples.

If it were me, I'd see what, if anything, has a different ohm value than it should. All things being equal, I would check the blower motor first. Easy to do. Just unplug it, put a fuse in, and see what happens. That ensures the blower is totally out of the circuit, and not affecting ANYthing. Does the blower motor have to be on, ie running, to cause the blown fuse? Has it blown the fuse with the blower motor turned off? I'd go after the blower motor first because it normally draws a good deal more current than the gauges do.

If the blower motor isn't it, then it's time to go after the gauge cluster. Check the two gauges it feeds. Is either one especially low ohms? Low ohms=higher current draw=blown fuse.

Finally, start tracing wires. These old wires tend to get cracks in the insulation. If you have a crack in the insulation somewhere, letting the metal strands of the wire touch ground, PFFT! Blown fuse.

Keep us up to date with what you find
Pat☺

PS: I just checked the schematics. As I read them, there's no fuse common to those two items, unless it's one of the fusible links feeding the whole system. The blower fuse is shown as a 20A fuse, the ENG fuse, that feeds the gauge set, is 15A. Can you tell us just what the fuse's NAME is? That will really help.
Pat☺

jgcalifornia

Thanks for the response.

FYI I don't use the blower, so it's not getting turned on/off.
Pics attached. The fuse in question is "gauges".

scope103

The "Gauge" fuse is switched, so things that want power only with key-on (like the door lock computer, dash lights, antenna control relay, light reminder ....) are hooked to it. That also includes the fan motor relay.

But that isn't going to help you too much; as Pat notes, you almost certainly have a damaged wire. Somewhere. So how to find it? You can wiggle wires until the fuse blows, but that will get old fast. Instead, find a high-current light bulb (a head-lamp bulb, or one of these: https://www.harborfreight.com/12-vol...ght-93904.html Replace the fuse with the light. It has such low resistance that your lights will work as normal, until the short happens, when your light will flash! Now get under the dash and start wiggling wires (in 1993, almost all of the wires powered by the gauge fuse are B-O (Black-Orange). But you're going to be wiggling bundles, where you might not even see the wire colors.)

Good luck!

86SR5PU

Check to see if the dimmer pot is intact. It may have come apart and found a ground.
Good Luck.

swampedout

I believe the technical term is "jiggle"

2ToyGuy

Well, it once was, but when you think about it, that term was taken over by the lovely, ummm...full chested...young ladies.

Now, I think "wiggle" is a better term to use, although the...ahem...other end... of the young ladies is rapidly taking that term over...
JUST my opinion, of course...
I AM a huge fan of the lovely ladies of any LEGAL age, BTW.
Pat☺

jgcalifornia

How would I "replace the fuse with the light"? And what is that going to do to my gauges?

Thanks!

scope103

A fuse has 2 pins. Pull out the fuse, and use the two wires of the lamp in place of the 2 pins of the fuse. If it were me, I'd take one of the burned-out fuses, and carefully trim it so I could solder the lamp wires to the two pins. Then I'd have a tool in case I ever needed it again.

Your fuse is a "zero ohm" jumper. You're replacing it with a low (around 5 ohms) resistance. The resistance of all your gauges will add up to something like 100 ohms. Using ohms law for resistive dividers tells you your gauges will be getting about 10% less voltage. Since they are perfectly happy with 12.3v (just battery) to 14.5v (alternator charging battery), they won't notice a 10% drop. With a total of around 105 ohms, not enough current will flow through your tester light to noticeably light it. But when something shorts out, the gauges are out of the circuit (otherwise the short would do nothing), and the full current goes through your tester lamp. The tester lamp lights with about 2-3 amps, well within the capacity of the rest of the wire.

Note this won't work if you were using it with a high-current load, like a headlamp or a blower. With a headlamp, the headlamp and your tester bulb would just share the voltage, each getting about 6v, so each will light dimly.