What's going on here?

[Skunksmash]

I'm having a strange electrical problem. Well, it seems strange to me at least. I did the H4 headlight bulb conversion on my 87. Bought some better headlights off ebay, and wow what a difference in night time visibility. I used those Hella brand relays, that have a fuse in them. Put them up by the battery, so they'd be easy to deal with in the event that I ever needed to work on them or anything. As you can see, they're melting. Wouldn't a short that was capable of generating that kind of heat, blow the fuses?

But it hasn't. You can see that one fuse, has just completely melted. Well, the plastic has melted off of the fuse, anyway. But the metal is still there, and still functioning. This all seems pretty strange to me. That the fuse didn't blow. They're just 25 amp fuses, for these 25 amp relays. Used 18 gauge wire, to wire up the headlight conversion. So I don't think its anything to do with the wire diameter.

[bbbc10]

Sounds like you need to upgrade ur wiring....when i put hids in mine i put in a relay harness an never had any problems with my wiring etc

[Skunksmash]

[Skunksmash]

Originally Posted by bbbc10

Sounds like you need to upgrade ur wiring....when i put hids in mine i put in a relay harness an never had any problems with my wiring etc

Well I did run all new wiring for the headlight upgrade. The old stuff just looked too old and crusty so I went ahead and replaced it.

[Mr.Chevy4x4]

What is the module right under your relays? EDIT: NVM, just realized it's your battery. It looks to me like the relays are getting extremely hot (more amperage than they are rated for?) Looks like the heat originated from the bottom looking at the one on the right. Maybe the fuse connectors are too small and are getting hot conducting the current?

Maybe get some 40/30 relays and in line fuse holders, and swap them out. Rated at 40 for startup and 30 continuous.

Mike

[69heavychevy]

I had a similar issue when I had my 69.

I had replaced all the fuses with brand new ones for piece of mind. Soon after I was melting wires but the fuses wouldn't blow (they were glass fuses).

After a few days of head scratching, I found that the new fuses weren't making good contact due to corrosion left behind by the original fuses I removed.

Cleaned up the contacts on the fuse box and problem was solved.

[Dead Parrot]

Put an ammeter on the headlight and check actual current draw. Depending on heat rating, 18ga wire maxes out around 16 amps.

Any chance the plastic is melting from exposure to battery fumes or indirect heat?

Did they melt immediately or several weeks later? If later, maybe battery fumes corroded the contacts leading to high heat.

[wilkin250r]

It's doutbful the negative battery cable is was the problem. Yes, it has some effect, but your typical automotive starter is about 500 amps. 25 amps is nothing. Even if your battery connection is so corroded it won't allow your starter to turn, you can still usually pull 25 amps off that terminal.

I'm more worried about the amperage in general, and your wiring. I don't know exactly what type H4 bulb you are using, but if it's a high-output, you might be pulling 100 watts, which is about 10 amps@12V.

I'm not sure how you're wired, if you have dual headlights or not, but if you have two of them, and you're pulling 20 amps, add some losses into the system, you could be very close to the max rating of that relay, and certainly higher than 16 gauge wiring. A lot of your heat might be coming from your wires, as copper is an excellent conductor of heat.

[Skunksmash]

Got some time to work on the truck today. Yes one of the wires, a hot wire, is getting very hot (temp). IR gun says 116 degrees, after being on for only a few minutes. The rest of the wires all say 75 degrees. The main wire getting too hot, is the long wire that I have running between the two sides of the truck. One wire powers the other side's headlights as well.

Hot wire on the battery was getting a little warm too, but I'm not sure if that's normal.

[Skunksmash]

Another thing I found:


One of my cheapo chinese headlight bulbs has completely crusted over with rust. The base of the bulb, is severely corroded. But NOT the electrical contact points. Maybe this is what I get for buying the cheapest headlight kit ebay has to offer. It came with 4 new headlights, that looked really good. As well as 4 new bulbs. To help hold the bulbs in, there is a rubber cap on the back of each headlight, which is about 3 inches in diameter. Each of those 4 caps is pretty badly melted, where it gets close to the bulb.

The bulb that I'm referring to with the rust, apparently melted its rubber backing cap so badly, that it began to allow moisture onto the base of the bulb. And the rust began aggressively eating up the base of the bulb. I have no idea if this could be related to my melting relay problem, though. The rusty bulb was still working fine.