Gen2 light and back battery charging

[SGT Estum]

Hi. I'm the proud owner of a new [to me] M1009. I picked it up for a good price from a private party because he was pulling his hair out trying to troubleshoot an electrical issue. Well, when I went to check it out the GEN2 light didn't illuminate when first turning the key on. I thought the issue could be simply solved by replacing a burnt out bulb in the GEN2 light socket. Well, I was wrong on that one.

I've been reading up on old posts regarding the M1009 charging system and I feel like I'm learning a lot, but I just can't quite pull it all together enough to make a diagnosis. Any help or suggestions would be greatly appreciated!! Here's my situation and the diagnostics I've done so far:

• The GEN2 light will not come on when the key is first turned to the RUN position (all the other lights do come on, though)
• I believe the back battery is not getting charged.
  • I checked voltage of both front and back batteries when the vehicle was off and both had about 12.78V. After driving around a bit, I shut her down and rechecked the voltage. Front had 13.20V and back had about the same.
• The 24V fuse in the bottom of the fuse block is good. I put in a new #10 fuse just to be safe.
• I checked the voltage at the 24V fuse (bottom left of the block) with the bulb in the GEN2 socket and the key in the RUN position (but engine off). It was 11.88V.
• I checked the voltage at the GEN2 light socket by probing either side of the bulb. It was 11.92V (so about the same as at the fuse) but the light is not lighting up. I then checked the amps at the GEN2 light socket and it was .359milliamps.

So I'm thinking the bulb isn't lighting up because the amps to it are too low. Also, shouldn't there be more like 24V to this socket than 12V? I'm thinking that it's about 12V because there's some line static or something energizing the circuit?

Would all this data suggest that it's the GEN2 relay or the diode that's gone bad?

Again, any thoughts or suggestions are much appreciated!!!

 

[NDT]

Is it possible the alternator itself is defective?

 

[ida34]

The bulb is 12 volt. No problem there. IIRC is the alternator is defective (regulator in the alternator) the idiot light will not come on. I am pretty sure you can check the wiring for the bulb by grounding the number 1 terminal on the harness to the alternator while it is disconnected. They key must also be on.

 

[DerangedMadman]

I just went through the same problem.

http://www.steelsoldiers.com/cucv/52396-gen-2-problems.html

This is the thread where I recieved lots of help. It has great information as well as the circuit diagrams.

Even though the bulb itself is 12V you should have 24V going to the socket.

Good luck.

 

[Warthog]

Sounds like someone (previous owner???) has been modifiying the electrical system

The 24v fuse AND the bulb should have 24v at all times because, in a stock system, it is being fed 24v from the 24v Positive Terminal Board.

First question. Do you want a stock system of a modified hack job?

Down load the Technical Manuals and print out each page of the Appendix for each of the electrical systems. (Appendix F in the -20 manual and Appendix E in the -34 manual)

Start with E-1 and check the battery wiring and go from there.

This may be a drawn out diagnosis..

Oh, by the way....Welcome to SteelSoldiers and.............

 

[burbn10]

Check the obvious stuff first. Make sure your batteries are wired in series and not in parallel, check the connectors on the alternators. Verify the isolated ground wires are properly attached. It's still weird that the Gen 2 light won't come on with low voltage, because that is what it's supposed to indicate... When I got my M1008, I had a bad rectifier bridge in Gen 2 and my light would only come on when I turned off the ignition....

 

[SGT Estum]

Sounds like someone (previous owner???) has been modifiying the electrical system

The 24v fuse AND the bulb should have 24v at all times because, in a stock system, it is being fed 24v from the 24v Positive Terminal Board.

First question. Do you want a stock system of a modified hack job?

Down load the Technical Manuals and print out each page of the Appendix for each of the electrical systems. (Appendix F in the -20 manual and Appendix E in the -34 manual)

Start with E-1 and check the battery wiring and go from there.

This may be a drawn out diagnosis..

Oh, by the way....Welcome to SteelSoldiers and.............

Thanks for the advice. I do not want a modified hack job, that's for sure! I don't think they've done much (if any) modification, thankfully.

I'm currently in the process of tracing the connections to make sure things are wired correctly according to the F-9 diagram in the -20 TM. I've started from the batteries and worked backwards, so far everything is connected correctly. I plan on tracing more this weekend, so I'll see what I can come up with and report back.

Also, as I'm highlighting the lines on the diagram as I trace through them. I'll post a scanned copy after I exhaust that diagram.

Do you think taking off the passenger side alternator and bench testing it at NAPA would help out or would it make more sense to trace circuits first?

THANKS!!

 

[SGT Estum]

I had some time to do a little more investigating and picture taking. I'm a little embarrassed to have not realized this sooner, but the "starter switch" on this vehicle appears to be installed to bypass the key ignition. It is wired up as such:

(black wire from near lower left fuse)----(starter switch)----(wire directly to starter)

I checked the voltages along this circuit and they are all 12V, which seems wrong since I believe the lower left fuse is supposed to be 24V. Furthermore, I checked the GEN2 relay and GEN2 diode, both appear to only ever have 12V (never 24 as I understand they are supposed to).

At this point I'm pretty confused.

 

[Crash_AF]

Question, how are your batteries hooked up? Are they hooked up:
Front Neg bolted to rad support
Front Pos to Rear Neg
Rear Pos to firewall junction block

Or are they hooked up Pos to Pos, Neg to Neg? It sound to me like your truck has been converted to 12V.

Once we know what mods have been done, we can help you straighten them out to stock or at least figure out what's been done so you can work from there.

In pic 4, you show two black relays. Is the silver starter relay in that same area? It sounds like someone bypassed it for that starter switch.

Later,
Joe

 

[Warthog]

As I guessed, the previous owner did a hack job on the wiring. He couldn'tfigure out the 24v and started modifiying. Anytime to see a bunch of yellow butt connectors and mysterious wires..................

Post some pics of the battery hookup, and any other "modified" wiring.

Like I said before this may be a drawn out diagnoses.

 

[SGT Estum]

The batteries are wired together in serial, and I do get 24V at some points in the electrical system that I've checked (e.g., the voltmeter in the dash).

I've got a few personal issues to tend to in the immediate future, so I won't have time to work on it until maybe next week. I'll trace some more runs and post more pictures then.

 

[SGT Estum]

Well, it's been a while but I wanted to update the thread. I did some tracing and determined that the previous owner had pulled the steering wheel at one point -- presumably to replace the blinker lever stuff -- and didn't get it back together correctly or botched the wiring somehow. Instead of doing it right, they just rigged up a starter button for the starter instead of rolling the key forward into the 'start' position.

Since this one was obviously modified (the starter button plus other stuff), I really got the itch to pick up another M1009 from GL. I'm now awaiting my EUC approval... exciting stuff!

Thanks to all for your suggestions/ideas. I *love* this site. I'm sure I'll be back with more questions on the next M1009.