HELP! No heat!!

[TrooperDouper]

I would like to run a problem by you to see if anybody has any insight. I have a 1996 Trooper. All of a sudden I have the following problems:

1. Alternator went bad. No output. Replaced. Works. Puts out 14.4V.
2. Heater fan does not come on. No voltage at the fuse. Fan is good.
3. 4WD light indicator on, even when off. 4WD seems to work normally
4. Battery indicator lit on dash, battery checks out good and system charging normally.
5. Brake indicator lit on dash, brakes work fine.

I am an electronic tech by trade and normally would troubleshoot this problem, but the dealer wont let me access their schematics and I know of no other source of that information.
My Chiltons manual shows an abreviated circuit diagram that made it look like something in the alternator could cause the heater problem, but I thought I ruled that out.
Anyway, if you have any insight it would be greatly appreciated because it's cold here and I need to get the heater running.

Thanks in advance,
Matt

[rodeo02]

Those dash lights on simultaneously usually indicates your charging system is not putting out 14v with the truck running (14v is what you need). Aftermarket or rebuilt alternators are almost always no good for these trucks.
G/luck
Joel

[TrooperDouper]

Originally Posted by rodeo02

Those dash lights on simultaneously usually indicates your charging system is not putting out 14v with the truck running (14v is what you need). Aftermarket or rebuilt alternators are almost always no good for these trucks.
G/luck
Joel

Joel,
Actually, I had it rebuilt by an independent shop. After replacing the belts and installing the rebuilt alt., I had the charging system checked at Autozone. It was putting out 14.4V average and battery and alternator tested good.

Thanks,
Matt

[2eyefishclaw]

DO NOT TRUST AUTOZONE FOR ANYTHING.
Take it to someone who is qualified to test it and with proper equipment oh and never trust autozone
the only good thing they sell is handcleaner and that is questionable. its putting out 14.4v what about under a load how many amps is it outting out thats the question?

[TrooperDouper]

Originally Posted by 2eyefishclaw

DO NOT TRUST AUTOZONE FOR ANYTHING.
Take it to someone who is qualified to test it and with proper equipment oh and never trust autozone
the only good thing they sell is handcleaner and that is questionable. its putting out 14.4v what about under a load how many amps is it outting out thats the question?

2eye, I gather that you don't think much of autozone lol. They put a tester on it that does a load test and I saw it putting anywhere from 20-60 amps throughout the test. Is this not a valid test?

[keithramsay]

Electricity is pretty much magic to me, but I'd be looking for something like a bad ground wire for those lights that stay on. About the heater fan: I had a similar problem with my 88 Trooper. Fan wouldn't come on upon starting the car. Then as I'm driving down the road freezing my butt off it would come on. I finally disconnected the wire from the fan to the switches and replaced it by tapping into a hot wire and running it to a rocker switch that I can reach under the dash. Now it is either all the way on or all the way off, but at least it works when I want it to.

[TrooperDouper]

It looks like Rodeo was correct. After extensive troubleshooting I found that the alternator is not lifting a ground path when charging properly. Most likely the rebuild wasn't done exactly correctly. I cut the while/green striped wire coming directly off the alternator and my indicator lights went out and the A/C switch and fan switch also started working. The alt/reg is still charging at 14V. I'm happy again!
Special thanks to 2eyefishclaw who was able to supply me with schematics that helped me understand Isuzu's odd wiring scheme. Thanks to everybody else who chimed in with ideas.

[jb4x4trooper]

if you have the jap. alt. ck and make sure both alt. wires are pluged up. I had the same trouble w/my 87. all my dash lights on but everything ck out. it should be the round plug. it goes to all the acc.s. the square plug goes to the batt. only. hope thats it!