Setting up a Military Dwell meter?

ih8pepl · Post by **ih8pepl** » Sun May 08, 2022 2:09 pm

I recently purchased a military Dwell meter and its a bit different than my good old Craftsman meter. My M38 is in perfect running order but I wanted to get familiar with the meter for future use.

I was following the DA 750-22 Pamphlet for set up, but it still leaves me with some questions. Connected using the Military Adapter set.

Meter, not connected, but how it should be set up for use when connected? sorry about the glare:

Meter not connected:

Meter Connected, needle adjusted to "Set Line" with dwell adjustment knob: Correct Set up? Seemed like I got a good dwell reading if it is correct.

This is my biggest question: Connected - engine running at idle. Um, that tach reading cant be right... Am I missing something? Lead from meter is attached to #1 spark plug adapter with the split sleeve clamp. Triple checked all connections/wire ~ maybe the meter is bad? Last documented use was 1970.

Post by **wesk** » Sun May 08, 2022 7:28 pm

Is it a Simpson unit?

ih8pepl · Post by **ih8pepl** » Sun May 08, 2022 8:06 pm

wesk wrote:Is it a Simpson unit?

Im assuming so, but any Simpson unit ive seen has round knobs. I cant find any markings on the unit aside from a postal stamp sized Army Calibration Tag that has "Type - Model 99664/CDTS" on the outside case.

Post by **wesk** » Sun May 08, 2022 10:23 pm

Take a look at the two Tach/Dwell Meter test set manuals I have loaded on our Downloads Page:

http://www.willysmjeeps.com/v2/modules. ... oad&cid=71

ih8pepl · Post by **ih8pepl** » Mon May 09, 2022 9:52 am

wesk wrote:Take a look at the two Tach/Dwell Meter test set manuals I have loaded on our Downloads Page:

http://www.willysmjeeps.com/v2/modules. ... oad&cid=71

I dont know how I missed that since I was printing up several manuals this weekend, but I did... Thanks Wesk!

ih8pepl · Post by **ih8pepl** » Mon May 09, 2022 4:45 pm

Followed the TM and still have that goofy RPM reading... Must be the unit.

Post by **wesk** » Mon May 09, 2022 5:06 pm

What exactly is the goofy RPM reeding?

Are you testing a stock 24V coil with stock contact points?

ih8pepl · Post by **ih8pepl** » Tue May 10, 2022 5:30 pm

wesk wrote:What exactly is the goofy RPM reeding?

Are you testing a stock 24V coil with stock contact points?

Yep, 24 Volt system and this is the idle RPM im getting from the meter. Even after rechecking all connections per the TM ~ I still get the same reading. No change on the dial if I switch from high/low setting.

Post by **wesk** » Tue May 10, 2022 8:16 pm

And you know that RPM reading is incorrect how?

And the rest of my 24V question? Stock distributor with contact points or a Pertronics type system.

ih8pepl · Post by **ih8pepl** » Wed May 11, 2022 10:18 pm

wesk wrote:And you know that RPM reading is incorrect how?

And the rest of my 24V question? Stock distributor with contact points or a Pertronics type system.

Going by ear ~ and I know my Jeep doesn't idle at 210 RPM. And switching to high sensitivity setting has no effect on the RPM reading. Needle just sits in the same spot. The TM doesn't mention troubleshooting incorrect readings aside from just rechecking connections.

And yes, its the stock distributor with points.

mdainsd · Post by **mdainsd** » Thu May 12, 2022 8:18 am

But the photo of the switch shows it on the 0-6000 position. so its idling fast at just over 1000rpm. hi - lo sensitivity doesnt change the meter range.

Post by **wesk** » Thu May 12, 2022 10:12 am

That's the problem with gauge photos that do not include the knobs. We have no way of knowing where the knob was when the picture of the 210 was posted. If it was really on the 0-6000 mark then his RPM is 1200 and not 210.

ih8pepl · Post by **ih8pepl** » Thu May 12, 2022 10:18 pm

Sorry for the bad lighting in the pic, the shadow is deceiving. The knob is on the 0-1200 range and showing 210 RPM.

Post by **wesk** » Fri May 13, 2022 7:40 am

My point was it is better to illustrate a meter reading while it is actually being taken with the meter switches in view. Your illustration shows the selector knob halfway between the 4Cyc. 1200 and 6000 ranges and the needle is on zero.

At any rate insure the ground connection you are using is the engine itself.

Have you removed the case and checked for the meter wiring diagram usually found inside? That diagram will tell you the make of the unit.

ih8pepl · Post by **ih8pepl** » Fri May 13, 2022 1:01 pm

The poor lighting and shadows from playing in the garage at 2am make the knobs look like they are out of position. But I followed the manuals set up instructions.

The dwell meter works 100% and matches my previous multimeter reading. Its just the tach side of the unit is being fussy for some reason.

I will take your advice and open the case on the meter - see if there is any corrosion or loose connections and give it another go.