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Old 04-08-19, 01:03
Wayne Hingley's Avatar
Wayne Hingley Wayne Hingley is offline
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Default Dead Batteries

Due to a slow drain-down my M38A1 CDN2 batteries, Iíve become used to disconnecting the batteries if Iím not going to use it for a week or more. Iíve been using the Jeep a fair amount this year, and Iíve noticed the time to completely drain the batteries dead had decreased to 1-2 days. Now the batteries arenít just low, but completely dead.

Chris V. had mentioned that he found a couple of different shorts in his wiring system that took a while to diagnose, but once repaired all was OK. So last night I got the multimeter hooked up and started disconnecting and reconnecting circuits and watching for continuity variations. I also visually inspected the entire wiring harnesses as much as possible. I even pulled the ignition switch to see if it was failing. No luck finding anything.

Today I explained the situation to Rob L. and asked for his thoughts. Rob recommended pulling the starter out and checking the switch for fine dust and copper particles that can cause a drain even while not in use.

So I pulled the starter and found a fair amount of dust inside the switch. I cleaned and polished up all contact surfaces and reinstalled. See photo of what it looked like when I opened it up. There was also some very light smoke stains from arcing visible, so I think this may have been my problem. With the extra use I have been giving the Jeep this year, I think the copper & dust finally got to a threshold in the switch that was killing my batteries.

Iím monitoring the batteries now to see if there is any drain... hopefully that was the issue (fingers crossed).

Thanks for the help Rob & Chris.
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Last edited by Wayne Hingley; 04-08-19 at 01:06. Reason: Add photo
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  #2  
Old 04-08-19, 01:52
rob love rob love is online now
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As I mentioned Wayne, this is a common problem on the M38A1s, and would imagine could be an issue on the M37 Dodge as well since it is a similar switch.



You may notice a small spark still when you hoook up the final battery terminal. That is a slight draw from the alternator, and is measured in milliamps, so not a real concern.
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Old 04-08-19, 02:24
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Lynn Eades Lynn Eades is offline
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Unless you have a crook diode in the alternator?
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Old 04-08-19, 13:58
David Dunlop David Dunlop is offline
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Wayne. I had the same problem with my M38CDN.

Prior to cleaning the starter switch, I had removed a battery lead from the cowl battery after checking all electricals were in off mode. When I jumpered a spare tail light bulb between the cable and battery post, the lamp lit,

Once the starter switch was cleaned up, and on mine I had to replace the two inner side insulator plates as they were charred so badly, I jumpered the bulb back in to check for leaks and the bulb did not light up. The electrical leak never returned.

David
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Old 09-08-19, 04:02
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Wayne Hingley Wayne Hingley is offline
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Quote:
Originally Posted by David Dunlop View Post
…I had to replace the two inner side insulator plates as they were charred so badly...
David; do you remember where you got the replacement insulator plates, or what that material is called? One of mine had deteriorated on one end. I did a temporary repair to it, but would like to replace them with new ones.

So far no problems with battery drain... Rob nailed it!
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Old 09-08-19, 05:06
David Dunlop David Dunlop is offline
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Hi Wayne.

When I cleaned the originals to see what they were, they were basically brown, phenolic circuit board material. I went to the local Radio Shack store at the time and bought a solid, copper plated circuit board kit that included a pen and a bottle of etching solution. I tossed the pen and applied the solution to the entire board (it was only 6 inches square) to strip all the copper off.

I then traced the pattern for the two plates onto the board and cut them out with a hack saw as I recall.

The copper etching solutions are readily available on the web, but I am not sure who in Canada still sells the solid, copper plated PCBís.

Hope this helps, Wayne.

David
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Old 09-08-19, 06:01
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Wayne Hingley Wayne Hingley is offline
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Hi David. Yes that helps. Circuit board is also what I thought of, but wasnít sure if/where it could be purchased.

I opened up a spare starter tonight, and the insulators in the second one are a slightly different material. These ones are shaped to wrap around behind the contacts. Seems like a better design. This spare starter was rebuilt at workshop 202 in 1979.
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Old 09-08-19, 06:18
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Wayne, how thick is the material? I have a source for excellent insulation material...
We often use G10 to replace old phenolic board and the like.
also probably have some micarta and other fibre based insulation kicking about.
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  #9  
Old 09-08-19, 06:46
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Wayne Hingley Wayne Hingley is offline
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Hi Chris. The circuit board style pieces were about 1/16" thick, but the style shown in post #7 is close to 1/8" thick. Maybe in metric dimension it would be considered 1mm.
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Last edited by Wayne Hingley; 09-08-19 at 06:51. Reason: units
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  #10  
Old 09-08-19, 16:13
Chris Suslowicz Chris Suslowicz is offline
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Quote:
Originally Posted by Wayne Hingley View Post
David; do you remember where you got the replacement insulator plates, or what that material is called? One of mine had deteriorated on one end. I did a temporary repair to it, but would like to replace them with new ones.

So far no problems with battery drain... Rob nailed it!
The insulating material looks like Tufnol (synthetic resin bonded fabric).

(The old "circuit board" is similar but uses paper instead of cloth as the matrix, but it's the same "Phenolic Resin" binder for the brown variety.)

http://ahistoryoftufnol.org/whatistufnol/

Birmingham: city of a thousand trades - some of which are still operating.

Chris.
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  #11  
Old 09-08-19, 19:21
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Wayne Hingley Wayne Hingley is offline
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Default Tufnol

Interesting. Thanks Chris. It seems there are several types of products out there that will perform the role needed. Hopefully one of these options will be available in small quantity, as I only need a few square inches, plus a spare bit for future use. Iíll do a bit of research on availability of these products to see what is available. Of course Chris V may come up with something as used in their industrial applications. Thanks to all for the input of information.
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