Low Voltage and instrument lighting issues

[forest522]

Good day everyone.

Long time reader and admirer of this site. Thanks to the common issues discussed and resolved here I have had this m1009 on the road for over 8 years including a move from PNW to the SW towing belongings in an m116 trailer and more recently a trip to VA and back to ABQ. She has been on countless trips to the mountains.

Side note to a recent thread - weak power has always been an issue on long grades, an extensive fuel system inspection, clean up, spin on mod and replacing of fuel tank and sending unit have "helped" to resolve that issue. Still, I live at 5500 feet elevation and travel into and around the 7000s frequently.

I digress...to say the least, I love this thing and keeping her running well.

After the recent trip back east and back, I decided to go with a Vintage Air install. And, "since I was there" I did the spin on filter, replaced the fuel pump and inspected, cleaned and replaced/upgraded wiring in areas needed.

I also rebuilt the alternator using the thread directions on this site. A great thread by the way. Thank you.

After buttoning everything up and checking/rechecking my work over the past several weekends, I started her up. To my surprise after all that work, she started right up after just a few of the priming cycles lined out in the tech manual. Easiest I have ever done after filter replacements, etc.

Here begins the diagnosis of a new problem (yay).

Symptoms...low voltage indicated on the meter and as measured from the pos terminal in the rear of the alternator - 11.9 - 12.2 volts.

No dash lights on the left side (speedometer) and no ALT light when turning engine on.

Work done so far: Removed fuse block, engine side, cleaned off all connections. Fiddled with the connector on the rear of the instrument panel...no improvement. Checked all fuses. Removed, examined and replaced Alternator...looks like it should...

So my thoughts are this: Replace the printed circuit ($60 LMC), rebuild the alternator again.

Am I missing anything? Thank you for reading this long post!

 

[DeadParrot]

Electrical working, upgraded/replaced wiring, now electrical problems?

Double check all your upgrades. Might have missed a connection or knocked one loose you didn't intend on touching.

No alt light. Verify the bulb is good. Oddly, the stock alt needs the little bit of current through the bulb to 'prime/excite' the alternator. Bad bulb or missing connection = no alt output. One side of the bulb should have battery voltage(12v) with key on - engine not running(Alt light on). Once the engine starts, the alt starts making power and balances out the 12v battery voltage and the bulb goes dark.

 

[forest522]

Copy that, will re-check and keep posted. A few pics to add to the situation...anyone else?

 

[forest522]

Description of photos: I had some "00" gauge cable on bothe batteries/starter previously, all was brought back into the new set up. The primary difference is the relocation of the house battery to the rear of the vehicle. Tied it in using 4 gauge and a 200 amp soleniod activated system.

As far as any changes to the charging system there have been none. Cable from alternator to the stock "positive bar" was upgraded a few years ago to 4 gauge (in second photo).

I wonder if the old original printed circuit isn't getting power to the bulb? Good point DeadParrot, i will check into that as I have always been a bit concerned about the brittle nature of that original plastic. And...wasn't aware of the "exciting" power needed for the alternator.

Thank you for your reply, very much appreciated!!

Forest522

 

[forest522]

So, an update. I replaced the printed circuit. The other one appeared to be original so a good place to start. Still no Gen 1 or 2 light upon turning key to 'on' position or after starting up - which by the way, she does fire right up. Just no charging from the Alt.

I changed both bulbs and cleaned the connections on the bulb twist sockets.

Does the Voltage regulator relay have a part in this? (I believe that is what it is called - right next to the starter relay)

 

[forest522]

I meant to say, does the Gen 2 relay have anything to do with this?

 

[ralbelt]

Following, what is the part number for the printed circuit. LMC has a few listed not 100% sure on which one. Thank You

 

[forest522]

The part number from LMC truck is:

"38-8036 - models without gauges"

for the year range 81 - 87. A whopping $69.95...ouch

Regards, Mike

 

[cucvrus]

I have used these on several occasions. They are "Made in USA" that is directly west of China. Made in a small little fish town by skilled craftsmen. Good Luck. But the circuit board fits and works. Now if just someone would make a decent bezel/housing.

 

[DeadParrot]

Another contact problem can be between the little wires on the bulb base and the contacts in the twist connector. Sometimes the little wires like to move sideways enough to miss the contacts. And I think the wires on the newer bulbs may be just a little thinner then the 80's versions. If you have a 6v lantern battery and a couple small jumper wires you can test if the bulb/twist connector combo is good. When I was going through the cluster on my recently purchased FD owned M1008, I had to pull some out of my spare parts supply for my old 75 Chevy C10 to find enough working ones to fully populate the M1008 cluster.

 

[forest522]

Thanks everyone for the advice. Latest update***

As with all things electrical...clean and check all grounds. Looking through the tech manuals, wiring diagrams, asking for help, tracing wires over and over...all these things are good in any event. And, you get to know the vehicle so much better. I did check all the bulbs, cleaned them applied a little dielectric grease to the metal contacts, made sure they were in contact with the new printed circuit...checked all the related wires...grounds...replaced the Gen 2 relay (behind the instrument cluster)...and so on.

Like many things, it ended up being simple. Here is the story.

As discussed above - this vehicle has had the Roscommon 12 volt conversion done. I did this immediately after buying the vehicle due to the crazy work that the PO had done in the engine bay (I bought it with only one alternator and one weak battery). I followed the steps to the number and spent a lot of time labeling and cleaning wiring. During the process it was clear then that the alternator needed replacing - there was only one and it was worn out. I bought one from O'Reillys, easy to do - basic 100 amp, Ultima #01-0136.

So fast forward 8 years...the alternator I purchased then from O'Reillys has seen better days. Replacing it with another I had picked from a 1008 in a junkyard, I rebuilt that unit to the specs here on the forum. Rebuilt it to the specs for a stock, unmodified CUCV...if you see where I am going with this.

The rebuild was for a isolated ground unit rather than the "commercially available, non-isolated alternator" referenced in the Roscommon conversion manual. So, after completely forgetting the work I did 8 years ago...I tried to install the newly rebuilt, stock CUCV type alternator into a 12v converted system that wanted an isolated ground alternator. I checked with the parts store, they tracked my purchase and wow --- lifetime warranty, handed over the first one, and boom -- a new/rebuilt alternator in my hands! Installed it...Gen 2 light came on, volts up to 14.3 after the glow plugs did their thing.

So - two things my Steel Soldier friends...(1). retain the manuals/directions for work that you do (in this case...refer to the Roscommon manual when troubleshooting charging system after this conversion) and (2). Remember the work you have done...its always helpful to keep notes and label things as you go along.

In the end, the good news is this. I have 14.3 volts charging the two red tops, all the systems are working, the Vintage air works great - the heater is really good! And...my wife likes it!

Regards, Forest522

 

[n8roro]

Replacing the bulb sockets helped me. The old ones were giving me intermittent issues even after cleaning. Cleaning the alternator connector could help as well.