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Discussion Starter · #1 ·
Had to replace my alternator because it went dead. I found some loose connections and replaced/repaired them along the fusible link area but even thought the alt is charging fine now, (actually 15v!) the fuel light, battery light, brake light and water separator light are all still glowing on the dash. What would cause all of these lights to go on simultaneously?
 

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I'd start by disconnecting the alternator and running the motor for seconds while observing the panel. On newer 1st gen troopers, there's a black/yellow wire associated with fuse 13 / 14 and the alternator which illuminates those lights. I'll see if my 86 manual shows anything additional or different from what I've written here. In the interim, I encourage you to open the pic links in the following link: viewtopic.php?f=1&t=56553
 

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Looking at the schematic, it shows the blk/yel wire originating @ fuse 15 and feeding the alternator / other components. Additionally, fuse 15 feeds fuse 12 which in turn powers those lamps with a single yellow wire.
 

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bellavesus said:
the alt is charging fine now, (actually 15v!)
I would be concerned with the 15v. In most, if not all 12v systems, that's an overcharge condition and can fry the alternator, damage / explode the battery, cause additional harm.
 

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Discussion Starter · #5 ·
Thanks for the help so far, Ive got 3 wires. One black w/yellow stripe, then a larger white wire in the middle, then a white w/green stripe. All of these have power coming from the alt when the engine is on. Is this normal? If i unplug the alternator, the lights on the dash stay on. The fuse 15 has continuity so its not a fuse issue I dont think. The alternator guy said he bench tested the alt and it worked fine for him. Jerry mentioned something about a relay internal to the alt that switches the warning light on if a certain current is not met. The alt has a new rectifier and voltage regulator, what else would need replacing?
 

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Those wires will be hot at the alternator when the engine is running. Fuse 12, which is fed by fuse 15, powers all the warning and indicator lights on your instrument panel. Those lamps are illuminated either by switches or predetermined changes in voltage. They all have on thing in common, a yellow wire originating from fuse 12. Fuse 12 is fed via a fat blk/yel jumper from fuse 15 which has connectivity to the alternator with a less than fat blk/yel wire. Looking at the schematic, the true warning lamps, not those like 4wd indicator which are driven by small switches, are also tied in to the "charge" indicator. The only reason I see for that is so when the vehicle is started and running, the charging voltage turns those lights off. They will come on when the voltage drops. Therefore, whatever the component is which has that responsibility inside the alternator is either defective or perhaps a bad circuit board behind the instrument panel. Am I right in assuming your 4wd indicator light is not stuck on as well as your low oil pressure light? I don't know if a bad or missing ground would cause this.
 

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WAG. Studying the schematic in more detail, the IG terminal on the ignition switch is fed by fuse 15 which also feeds fuse 12. The IG (ignition) terminal on the switch is basically the on position and/or accessories position. The R terminal is run which is not the same as on. When you start the vehicle, the key sequence goes from on (lights on) to start to run (lights off). Might be nothing more than a defective key switch.
 

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Discussion Starter · #8 ·
You are right, the oil pressure and 4wd lights are not on. From the 3 wires off the alt with the engine running I am getting 15.9v from the white green, .05 from the middle white, and a dropping voltage that does not stay constant on the black yellow.
 

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bellavesus said:
You are right, the oil pressure and 4wd lights are not on. From the 3 wires off the alt with the engine running I am getting 15.9v from the white green, .05 from the middle white, and a dropping voltage that does not stay constant on the black yellow.
I take it white/green is the charging wire to battery (B terminal at alternator)? That's way too high. Should be 14.2 - 14.5 or so at its peak. Do you have the basic lead acid battery? Are you testing the voltage across the battery terminals at 2,000 - 3,000 rpm? Do you have a load on the system? How long after startup did you perform the test?
 

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Discussion Starter · #10 ·
The previous voltage measurements were taken with the car running, but unplugged from the loom. I remeasured the voltage at the alternator with it running and connected and there is 15v+, 14v+, 15v+ across them. I have a standard autozone diesel battery that I put on a recharger before I reinstalled the rebuilt alternator. The RPM's are around 900 or so while I am testing, which is about a minute after starting. There are no accessories switched on or lights when I used the multimeter on the battery.
 

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Discussion Starter · #11 ·
I replaced the Relay, but the water separator and fuel and battery lights are still on-just dimmer.
 

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Discussion Starter · #12 ·
Heres a video of lights on the dash. They dim after the car is started, and if I flip the heater/vent switch over to "vent" they pretty much go off!

 

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Was it a new altenator or a reconditioned one?

Also have you measured the voltage accross the battery stopped, running, with various electrical items switched on, and again with stuff switched on and the revs raised to 2000 rpm. You should get a steady 14.4 volts. If the voltage drops with the revs or as things are switched on I would reckon you have a lazy altenator.
 

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Discussion Starter · #14 ·
I had the alternator worked on, its the original with new regulator and rectifier. Its putting out 15.8 volts, which is too much! I took it into the shop, and he showed me that it was charging fine with the sensor wire connected. I believe I have an issue on the sensing circuit.
 
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