Electrical Gremlins

[Roadrunner 161]

1986 M1009. Freshly rebuilt 6.2 and TH400. After driving for a day the GEN 1 light did not come on and volt meter stopped working. I have charged batteries, had GEN 1 rebuilt and reinstalled, checked all fuses, did Doghead relay conversion, changed all bulbs in dash, tested all circuits for continuity, checked/tightened all electrical connections under the hood and kicked the left front tire.

GEN 1 light still won't come on (tested back of alternator with screwdriver and it is not charging). Voltage check shows 14.6 V on rear battery and 11.6 V on front battery. Volt meter still won't come on. Vehicle starts fine with charged battery. The man that rebuilt GEN 1 has been rebuilding alternators/starters since 1990 and said it was good to go. What am I missing?

 

[Roadrunner 161]

Took apart a bunch of connections and cleaned with CRC. GEN 1 light still is not on and volt meter still does not come on. What is the logical relationship point to check between GEN 1 and volt meter?

 

[DonK]

"Download the TM's. Read and Understand them." Quote from BTDT...

 

[mistaken1]

What about the big ground from gen 1 to the engine?

 

[BIG_RED]

Check the bulb. If the bulb is burnt out(or contacts are dirty, etc), the alt won't start working. Usually alts need juice from the batt to "excite"(start) the electric magnet rotor that makes juice. Sometimes, at higher rpms there is enough "remaining magnetism" in the coils to make a voltage and start the alt up when you get it spinning at high enough RPMs (called Self Excitation", does not always happen, can depend on how long it's been since the alt was last used). There are 2 little wires in one plug connecting to the back of the alt. Remove that plug from the back of the alt and get your multimeter. One should be hot (+12) all the time, one should be hot through the dash light only when the key is turned to "run" (I don't remember which one is which, but it's easy to figure out). Once you figure out which one is always hot, leave it alone. Grab the other one. It connects to +12 through the dash light when the key is set to "run". It supplies power to excite the alt. The power passes through the lightbulb to get to the alt, so the light glows when the alt is being "excited". Once the alt is up and running, it generates it's own power, so there's no need for it to suck power through the lightbulb (so the light goes out). Try putting the key in the ignition, switching it to on and having someone sit in the drivers seat while you ground that wire for a second (touch it to something metal, use a short wire if you need to). If your truck's wiring is good (and the rebuilt alt is the issue) the alt1 light will come on. If not - Take that alt back. Here's a simplified diagram for you, incase you wanted one: http://www.expeditionlandrover.info/LR.images/DelcoWiring.jpg Good Luck!

 

[Warthog]

Check the very top fuse for the heater motor. The Gen1 and heater share that fuse.

 

[mistaken1]

GEN 1 light still won't come on (tested back of alternator with screwdriver and it is not charging).

By the way, how do you measure voltage with a screwdriver?

 

[cpf240]

By the way, how do you measure voltage with a screwdriver?

Got sparks? Then you've got voltage...

 

[Roadrunner 161]

I was checking to see if my alternator was "excited". It wasn't.

I will try these suggestions tomorrow. Thanks Gentlemen.

 

[wallew]

do the fuel gauge and the voltmeter work at all?

If not, check up under the dash on the drivers sidewall. There is a ground that can be bad - broken - etc and it MAY (probably not) be the issue -

ain't electrical issues fun??

 

[mistaken1]

Got sparks? Then you've got voltage...

Ahh so the point is to create a deliberate short circuit and then look for the arcs created when trying to break large current flows?

In my world short circuits are a bad thing, they cause short circuit current that damages things (in this case fuses, fuse links, wires, alternators not to mention screwdrivers).

Wouldn't it be easier (and less destructive) to use a voltage meter to check for voltage?

 

[cpf240]

Ahh so the point is to create a deliberate short circuit and then look for the arcs created when trying to break large current flows?

In my world short circuits are a bad thing, they cause short circuit current that damages things (in this case fuses, fuse links, wires, alternators not to mention screwdrivers).

Wouldn't it be easier (and less destructive) to use a voltage meter to check for voltage?

Didn't say I thought it was a good idea...

 

[mistaken1]

Didn't say I thought it was a good idea...

LOL That's true.

 

[1stSarge]

But it is kinda fun…

 

[Roadrunner 161]

All bulbs are working except GEN 1 and volt gauge light. Volt gauge also does not work. I haven't been able to check suggestions yet due to work schedule.

By the by, I was able to rebuild the motor using all new pistons, rings, cam, bearings, gaskets and having heads and block tested and crank turned for $685. Thanks to being able to buy parts from Steel Soldier members.