Can I use a regular 12V dwell meter on the M38A1 24V

DaveM38A1 · Post by **DaveM38A1** » Fri Dec 29, 2023 4:59 pm

If I just connect to the battery that goes to ground, can I use a 12V dwell meter on my 24V M38A1. Wanted to give it a really good tune up with the dwell meter and the vacuum gauge. Will it work, or will the ignition burn it up?

Thanks,

Dave

Post by **wesk** » Fri Dec 29, 2023 10:06 pm

Are you aware the dwell meter is designed to be used for setting points on a distributor that has an external adjustment capability. A correctly gapped contact set that has been carefully inspected for general condition and wear has no need for dwell testing on an engine with a non-external adjustment capability.

As for damaging your dwell meter with a 24V system it depends on what dwell meter you have and how it is powered and connected to the subject vehicle.

DaveM38A1 · Post by **DaveM38A1** » Sat Dec 30, 2023 8:22 am

So, if I have adjusted the points gap correctly, I don't need to check the dwell. I was going to use the dwell/tachometer to set the idle speed and the vacuum gauge to set the idle speed and adjust the carburetor. Right now, I have to give the Jeep gas slowly, or it will bog down. I may need to rebuild the carb, or it may just need adjusting.

Thanks,

Dave

Post by **wesk** » Sat Dec 30, 2023 12:52 pm

So, if I have adjusted the points gap correctly, I don't need to check the dwell.

And

carefully inspected for general condition and wear

Dwell and tach readings can be helpful when modifying your tune-up specs to accomadate changes to components and other changes like increasing compressions or fuel octane. But you must be sure of the specific tach/dwell meter connection restrictions for the meter you are using. IE input voltage restrictions or high tension voltage restrictions peculiar to your test set. Some meters have internal batteries and others use the host vehicle's battery.

The Army issued a line of high quality meters under FSN 4910-788-8549. These were commonly made by Simpson, or AUL along with several other manufacturers but each had it's own user manuals and there were significant differences between them.

Also if you still have all original harnesses and leads then the Army harness adapter kit is needed for use with test meters.

DaveM38A1 · Post by **DaveM38A1** » Sat Dec 30, 2023 3:10 pm

I have the test leads set. We used tat set to troubleshoot the ignition system. I would love to have a military meter if I could a working one at a decent price.

Dave

Post by **wesk** » Sat Dec 30, 2023 4:32 pm

There are 4 currently on Ebay: https://www.ebay.com/sch/i.html?_from=R ... r&_sacat=0

DaveM38A1 · Post by **DaveM38A1** » Sat Dec 30, 2023 4:53 pm

Thanks,
I'll get one.

Thanks,

Dave

Post by **wesk** » Sat Dec 30, 2023 5:01 pm

I would try to at least contact the seller before sale and ask if he has used the tester successfully. Note that a couple of the Ads show the term "Untested".

Post by **wesk** » Sat Dec 30, 2023 10:36 pm

On another Dwell/TACH note I have had a Sears Diagnostic Analyzer for over 20 years that I have found very helpful and surprisingly versatile. It handles much more than just Dwell/Tach.

DaveM38A1 · Post by **DaveM38A1** » Sun Dec 31, 2023 6:58 am

That does look handy,

Dave