Electrical System Problems

People all over the place have been stunned by this one...let's see if I can find it here!

When I turn on my headlights, my radio goes off then comes back on. Both turn signal indicator arrows light up, and the rear defrost button lights up dimly. If I turn on my brights the radio goes off and stays off, and those other lights come up brighter.

I took out the radio, and now, when I turn the lights on, they don't come on, but the relay goes nuts, all those other indicator lights come on full, there is a strange hum from the fuse box in the car. If I pull the 15a Tail/Illumi fuse, the hum goes away. If I plug the radio back in, the hum goes away, but nothing else changes. If I turn the key to the "ON" position, the hum goes away, but nothing else changes.

Anyone? I've got nothing else on this one!

I have a 1998 Rodeo LS 4x4 V6.

Sounds like the battery is dead or dieing and the Alt is dead or dieing too (it is overcharging or under charging).

Isuzu's do strange things when the electrical system is weak.

Also if you have an trailer harness unplug it.

What is the history on the alt? How many miles?

Well, that's the thing.

The batt is brand new, and the alt is brand new. Truck has 100k, batt/alt have less than 500. This happens with the car running or sitting still.

I believe it is a short somewhere...but I just can't seem to find where.

What brand alt? How much did it cost?

If you search this forum a little bit you will see that Isuzus don't like cheap after market alts.

how about the trailer harness? do you have one plugged in?

http://www.automotiveforums.com/vbulletin/showthread.php?t=606463

http://isuzufaq.ibctech.ca/electrical.pdf

DOH! I forgot to ask about the trailer wiring harness in the post on the planet.

I doubt its the alt since it happens even with the truck not running.

I'm sticking with my earlier suggestion of shorted or burnt wiring in the headlight ciruit (providing that it doesnt have trailer wiring thats gone bad that is). But also adding possibly a bad combination switch.

Nope, no trailer harness! I'm looking into a short...I'm almost positive that's what I have here. It has to be a ground short....

sounds like possibly poor contact in a relay maybe some corrosion or rust
maybe even just worn find the one that is buzzing and try swapping it out with another one like it

I have identical problem with my 1998 Isuzu Rodeo. Were you able to find a solution?

It ended up being a bad ground on the blower fan. The ground is located behind the glove compartment. Take the door off, and you will see the blower. Off the left side, is a wire that comes off, and connects to a metal cross piece that runs behind the dash. Mine was broken, and very loose.

I was planning on checking all grounding points next...this helps, at least feels like I'm on the right track. Thanks!

It ended up being a bad ground on the blower fan. The ground is located behind the glove compartment. Take the door off, and you will see the blower. Off the left side, is a wire that comes off, and connects to a metal cross piece that runs behind the dash. Mine was broken, and very loose.

I found the blower, but there is not wire on the left. The only wire I could see that is connected to the blower is the one on the bottom of the blower to the right, two wires to be exact, one is blue, the other one is blue/black. I can read 12V across the two wires, but the blue/black wire does not share a ground with the rest of the vehicle, something like 300ohms. Where does the blue/black wire from the blower go, any ideas?