89 - hot headlight switch and light fuses - need help

[JP700]

I have an 89 (targa) in which all lights (headlights, fog lights, parking lights and dash lights; high beam and low beam) starting occassinonally dimming for a second or two after being on for 10 minutes or so. The fuses (actually the screws holding the fuse buses in) for all lamp circuits get so hot you can't touch them, and the headlight switch also gets hot (but not so hot you can't touch it). Thinking it may be an alternator issue, I turned the lights on with the car not running, and sure enough, the same issue happened. This suggests to me that it's either a short or the headlight switch (and not the alternator or VR). I'm not sure how the power flows though (fuses, then switch?), which makes this hard for me to diagnose. Any help would be greatly appreciated.

[porwolf]

If the fuses and/or the fuse holder brass posts get hot it is a poor contact issue. First I would make sure all the wire ends going into the brass posts are clean and screwed down tight. Then I would take the fuses out and bend the contact blades inward to apply more pressure on the fuse ends. I would rotate the fuses several times to ensure good contact to the blades. If all these contact areas are performing as originally intended the fuses and the brass posts should not get hot. If they do there is also a fire danger!

[JP700]

Yup - a little sanding to the copper where the fuses make contact, and the fuses themselves, as well as tightening up the screws that hold the wires into the bus, resulted in no heating of the fuses or busses. THANKS. Headlight swtich still gets really hot though. Thinking I should replace it...

[david482]

A good fix for the hot headlight switch is to add the relay kit.

[T77911S]

all good advise.

resistance causes heat, along with current, but that has not changed from what was designed. this is what causes fires. wires get hot, insulation melts then the wires short.
where it is getting hot is where the resistance is hi.

cleaning the fuse block is a good start.
also remove the screws and clean the ends of the screws. clean the fuse ends and the clips.

if the head light switch is still getting hot, replace it.
make sure the wire terminals to the switch are clean.

i would also go through the wiring and clean the grounds and contacts for the lights.
old bulbs can also have corrosion and cause resistance.

even though i would say the alt has nothing to do with this, anything is possible. just put a meter on the battery while the engine is running and the lights on.

[porwolf]

Originally Posted by JP700

Yup - a little sanding to the copper where the fuses make contact, and the fuses themselves, as well as tightening up the screws that hold the wires into the bus, resulted in no heating of the fuses or busses. THANKS. Headlight swtich still gets really hot though. Thinking I should replace it...

Relay kit is imperative and not expensive. Otherwise you run all that headlight current through the light switch and the turn signal switch. With the relays all the current bypasses the switches and goes diectly from the battery to the headlights. Only the small relay coil current has to go through the switches.

[JP700]

I ordered the relay kit and if the switch doesn't cool down using that, I'll order a switch too. Thanks to all for your input.

[T77911S]

i would order the switch first. if it is bad, it is bad and needs to be replaced.

[Bill Jennings]

I would order both switch and relay kit and replace together, why put all that load through the new switch and clean up and check all of the lighting contacts as recommended above, while you are in there check the rest of the wiring while you are at it.

I'd also have a fire extinguisher handy at all times as I would rate the fire risk higher on your car than most.

Cheers
Bill

[porwolf]

Originally Posted by porwolf

Relay kit is imperative and not expensive. Otherwise you run all that headlight current through the light switch and the turn signal switch. With the relays all the current bypasses the switches and goes directly from the battery to the headlights. Only the small relay coil current has to go through the switches.

Just to clarify here. For myself I built my own relay kit and wired it such that the light current goes only from the battery through the relays to the high and low beam lights. So in my case the light current does not even go through the light switch, so the switch cannot get hot. I wanted the main light current to go through as few contact areas as possible. I also used four relays, on each for the two high beams and the two low beams. I just wanted to as little current as possible going through the relay contacts. Relays are cheap, why not. Of course, I have all four light wires from the battery fused individually close to the battery.

[T77911S]

thats fine. the wires need to be fused before the relays. closer to the battery the better.

i am not a fan of modifying the original wiring unless it is a major problem with the design. like on the 930's. 2 fuel pumps thru one fuse. even new, the fuse gets very hot from too much CURRENT. if you put in a new light switch and it gets hot from hi current, that is one thing, but to put in relays just because the light switch is bad, that is another. just me personal opion.

i will tell you this. i just bought an 86 930. the original wiring is unmolested as far as i know except that a switch was spliced into the wirper wiring i guess to fix something.
it really makes the car when you can open the hood and there is not a lot of hacked in "mods" to the wiring.

[porwolf]

Originally Posted by T77911S

thats fine. the wires need to be fused before the relays. closer to the battery the better.

i am not a fan of modifying the original wiringg unless it is a major problem with the design. like on the 930's. 2 fuel pumps thru one fuse. even new, the fuse gets very hot from too much CURRENT. if you put in a new light switch and it gets hot from hi current, that is one thing, but to put in relays just because the light switch is bad, that is another. just me personal opion.

i will tell you this. i just bought an 86 930. the original wiringg is unmolested as far as i know except that a switch was spliced into the wirper wiringg i guess to fix something.
it really makes the car when you can open the hood and there is not a lot of hacked in "mods" to the wiringg.

The only changes to the original headlight wiring I did was to disconnect them from the fuse bank and connected them to my new relay outputs. The relay inputs came directly from the battery, fused of course. The relay coils were then fed by the fuse bank where the headlight wires were connected originally. I even left the old fuses there. Therefore no high currents run through the headlight switch or the directional light switch at the steering column.

[JP700]

Thanks for everyone's input - you all make good points. Will replace the switch as well - no sense in increasing fire risk...