Question for other Trooper owners...


New member
I'm trying to sort out an electrical gremlin and thought some of you may have had a similar situation and could provide some insight.

My Trooper is a 94 S; 216,000 miles; 6 mo old battery. Recently I started hearing a relay clicking. The blower motor soon stops blowing and the fuel, brake, battery, and cruise control lights come on. The amps drop from a normal 14 to 12, but never go below 11-12. I've ordered a couple of new relays (it seems that most of them in this vehicle are the same part number.)

The question is, am I correct in thinking that this is just a relay problem, or is the alternator getting ready to fail? I don't know how old the alternator is. I've owned the vehicle for about 5 years and I'm not sure when the previous owner replaced it.

I did have a spare relay in the underhood fuse box, but the same thing happened with this relay. I don't know if that relay was bad, as well. I was going to swap it with another relay, but the others seemed to be more critical.

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I don't think it's either. I've not done a lot of electrical trouble shooting on the 2nd gens but many folks over on the planet have. If the alt is going up you'll have fuel pump problems. They run the fuel pump relay off a separate wire from the alt as a fire safety feature. Have a wreck. Engine stops running so does alternator. Fuel pump stops and no fuel pumped to make a fire.
Put the question up there and I'm sure somebody has already been through it. Isuzu lumped some seemingly unrelated stuff together in circuits in the second gens. Sometimes you get flashing like that and It's a trans sensor or something. HUH? Isuzu switches the ground side of most stuff on their trucks so electrical gremlin chasing is a little different on those trucks. The folks on the Planet can help. Also Isuzu made some really good electrical trouble shooting manuals for their trucks. Find one if you can.


New member
Thanks. I have posted over there. Hopefully I'll get some direction. Where would I go about finding one of those manuals?


They show up from time to time on epay + in the clasifieds on the planet. WTB ad there might be a good idea. May be able to get a new one from Helm inc. No idea if they are still avail. Helm is spendy for any manual though.


New member
Im assuming you mean volts not amps. Low voltage in a fuel injected vehicle causes all sorts of odd issues. 11-12 volts running is not enough. Every piece of code in that computer is written to reference 13.4-14.7 volts as the running power source.

Take the alt off and get it tested.


The Credible Hulk
My alt went out on my 93 last year, but it was going bad for a year or two. No relay-clicking symptoms like you describe, other than the wipers and windows ran slow. But I didn't even notice that until the new one was in and everything ran faster.

That alt is not the easiest to get to, take off the front pass wheel and work from the side and below. But it is easier to do it on your terms than on the road when it goes out for good, like mine did in Moab. I had the pleasure of replacing mine in a motel parking lot.

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