Melted Fusebox

[BoldUlysses]

It's been this way for some time (back when the car was last driving—in '04). Now I'm finally addressing it.

The dash/parking lights wouldn't come on, and the culprit was the fuse you see. The metal part wasn't broken, but the left end was corroded and melted, which caused the break. I replaced it with a new one, and immediately smelled burning and the terminal area was too hot to touch.

Do I have a short somewhere in the dash/parking light circuit? If so are there any typical places to look?

I can fix mechanical stuff, but electrics are a bit of a black art to me. Hence the reason I'm restoring a Z and not something with Lucas electrics.

[d240zx2]

MSA has an upgrade for this that provides modern blade fuses instead of the old glass fuses. It's well worth the price. I doubt you have a wiring issue.

[BoldUlysses]

I was going to ask about that but I didn't want to pepper you guys with too many questions. Awesome—I'll look into that for sure.

Why would the fuse terminal get so hot if I didn't have a wiring issue? Heat = too much current = short somewhere. Right?

[Carl Beck]

Why would the fuse terminal get so hot if I didn't have a wiring issue? Heat = too much current = short somewhere. Right?

Heat = too much resistance. Too much resistance in the loose and corroded fuse terminal on one end.

Yes - a dead short will draw too much current and because the wires are too small to carry it - they get hot, and in a good circuit the fuse will blow. If there is no fuse between the battery and the short in the circuit - then the wires will melt.

FWIW,
Carl B.

[SteveJ]

Matt, look for my Sold on LEDs thread. Replacing the incandescent bulbs with LEDs will drop current flow through the circuit greatly. Also consider getting the parking light relay harness from Dave Irwin, aka Zs-Ondabrain. Also, unless you have more fuse boxes lying around, you might need to get the replacement fuse box from MSA.

[FastWoman]

FAIW, while that fuse box might be slightly unsightly, there's nothing wrong with it functionally. Just clean the metal with distilled vinegar, dry, and lightly coat with a bit of silicone dielectric grease. Then you'll have excellent contacts with very little resistance and therefore very little heat.

[beermanpete]

FAIW, while that fuse box might be slightly unsightly, there's nothing wrong with it functionally. Just clean the metal with distilled vinegar, dry, and lightly coat with a bit of silicone dielectric grease. Then you'll have excellent contacts with very little resistance and therefore very little heat.

Unless the clips have lost their temper. When they overheat they can lose the spring temper and the pressure to hold the fuse will be too light and the resistance will be high enough to allow a recurrence. In this case replacement clips could be used if you want to keep the OE fuse box badly.

[BoldUlysses]

Heat = too much resistance. Too much resistance in the loose and corroded fuse terminal on one end.

Yes - a dead short will draw too much current and because the wires are too small to carry it - they get hot, and in a good circuit the fuse will blow. If there is no fuse between the battery and the short in the circuit - then the wires will melt.

FWIW,
Carl B.

Carl— Thanks for clearing that up.

Matt, look for my Sold on LEDs thread. Replacing the incandescent bulbs with LEDs will drop current flow through the circuit greatly. Also consider getting the parking light relay harness from Dave Irwin, aka Zs-Ondabrain. Also, unless you have more fuse boxes lying around, you might need to get the replacement fuse box from MSA.

Good tips, Steve. I'll look up your thread. LEDs aren't really considered by the BMW world because of the cars' self-monitoring systems—if resistance in a circuit drops too low (either by a light out or installing LEDs), a dash warning trips on. But our Zs don't have that "protection."

FAIW, while that fuse box might be slightly unsightly, there's nothing wrong with it functionally. Just clean the metal with distilled vinegar, dry, and lightly coat with a bit of silicone dielectric grease. Then you'll have excellent contacts with very little resistance and therefore very little heat.

Good to know. I might do that just to get the car running. Will definitely replace the fusebox in the long run.

Unless the clips have lost their temper. When they overheat they can lose the spring temper and the pressure to hold the fuse will be too light and the resistance will be high enough to allow a recurrence. In this case replacement clips could be used if you want to keep the OE fuse box badly.

Lol. The OE fusebox is trashed, cover melted, etc... Good points about the temper, though.

[SteveJ]

Good tips, Steve. I'll look up your thread. LEDs aren't really considered by the BMW world because of the cars' self-monitoring systems—if resistance in a circuit drops too low (either by a light out or installing LEDs), a dash warning trips on. But our Zs don't have that "protection."

To be pedantic (a trait that I'm good at ), LEDs have high resistance and low current. An incandescent bulb is a piece of wire that glows because of low resistance and relatively high current. As you noted, the Z does not monitor resistance in lighting circuits, so there are no worries about using LEDs. Though, I believe LED vendors are also selling devices to fool the onboard systems that do monitor resistance. It would essentially be a bypass for the circuit.

[beermanpete]

The only issue with the LEDs is the turn signals. Some flasher units are load (current) dependent and won't flash if the load is wrong. You can get flashers for different loads or get the heavy duty type which is not load dependent.

[SteveJ]

The only issue with the LEDs is the turn signals. Some flasher units are load (current) dependent and won't flash if the load is wrong. You can get flashers for different loads or get the heavy duty type which is not load dependent.

Very true. I put the part number in a post in the Sold on LEDs thread. It was the Bussmann 232.

[sparegolfer]

Very true. I put the part number in a post in the Sold on LEDs thread. It was the Bussmann 232.

bad contacts in the turn signal lights listed under the common z car problems. Maybe take a look at all your parking lights and see if you have some of the same problems.

[Walter Moore]

Wow, what are the odds of that? My fuse box looks exactly like that!
Apparently that is usually the first fuse to burn out. It must be a high load circuit.

I just replaced the fuse on that circuit with an in-line fuse holder. However after a couple of years the remaining clips were so weak that they stopped holding the fuses tight and they started to heat up as well. I "fixed" it by pulling the battery out, taking out all the fuses, and then using a plastic wire tie around the base of each clip to clamp every fuse in place. (It will be a real pain to replace any of them now...)

I know however that what I did is only a temporary measure. Eventually the MSA fuse box upgrade is probably in my future. You might want to bite the bullet and replace the fuse box now...

[Darrel]

Matt, look for my Sold on LEDs thread. Replacing the incandescent bulbs with LEDs will drop current flow through the circuit greatly. Also consider getting the parking light relay harness from Dave Irwin, aka Zs-Ondabrain. Also, unless you have more fuse boxes lying around, you might need to get the replacement fuse box from MSA.

This along with the headlight harness and for the modern blade fuses get the msa fuse block. As Dave has explained in previous threads all the current to run the PL and HL run through the fuse block and the combination switch. If you take the clam shell off the steering column you will see the white and red wire deformed from all the resistance. The msa fuse block will curtail much of the resistance, but you still have the power to the HL and PL running through the combo switch.

[RedBird64]

Hi,
I realize this is an aged thread, but it's ironic I'm repairing a damaged fuse box in the same location. What is MSA?

[Darrel]

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