Temp gauge explodes

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Txjeeper81
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Temp gauge explodes

Unread post by Txjeeper81 » June 26th, 2017, 7:51 am

Yes the title is correct. While running a m151a2 that I just recently got back on the road I noticed the volt gauge was past the red and when I mean past the red you could have added another color to the gauge. At first I figured this was a faulty gauge as the A2 had been sitting for many years and a few gauges no longer work. So I decided to turn off the battery kill switch that this A2 as installed when I did I noticed the engine picked up speed and when I turned the kill back on the engine idle slowed down. So I figured that the alternator was putting a load on the engine to charge the batteries. After turning off the the kill for a second time and not seeing any change in the gauges I turned the kill back on and about 10 sec later the water temp gauge literally exploded and the face of the gauge blew off smacking me in the wrist and then the internals of the gauge caught fire. The Gauge looked like a flash bulb going off right before the gauge caught fire and blew apart.

Now talking with some friends we figure that the Alternator went to ground and that's what shorted out the gauge. the next time work on this A2 I will pull the alternator off and take it to a shop to be tested. This was a first for me I have never have I seen a gauge explode let along get hit by the parts.

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Fil Bonica
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Re: Temp gauge explodes

Unread post by Fil Bonica » June 26th, 2017, 9:27 am

Sounds like kill switch does not shut everything n the battery circuit.
The alternator was running without a load and voltage rose and causing the damage.
Exactly where is the cutoff in the wiring?
Typically it should be on the groound sde of the battery.

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Re: Temp gauge explodes

Unread post by rickf » June 26th, 2017, 9:35 am

I can't tell you how many times I have said not to disconnect a battery while the vehicle is running, it will cause a spike in the voltage. This spike can be considerable, 75-100 volts. It will a lot of the time take out the voltage regulator at the same time. It sounds like the voltage regulator was already gone from the volt meter readings. If you had done this with the battery cut off before that is what may have done that.
1964 M151A1
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Txjeeper81
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Re: Temp gauge explodes

Unread post by Txjeeper81 » June 26th, 2017, 10:54 am

Rickf: I have never done this before with the engine running. I only did it when I saw the gauge was way past the red line on the gauge. I thought maybe there was something wrong with the new batteries that had been installed by the previous owner.

Fil: The kill is on the positive side has far as I can remember but will check on which side the previous owner installed it on. Every vehicle I have seen or had with a battery cut off installed was on the positive side of the system not the ground side.

from both of y'alls responses It sounds like the regulator had already gone out and when I screwed with the battery cut off I fried the gauge and god knows what else. This all happen in a matter of seconds I should have cut the engine off before messing with the electrical system but I did not. So I screwed up and will never do that again.
CSM In the Texas State Guard
National United States Armed Forces Museum
1943 MB W/Trailer "Puddle Jumper II"
1968 m274A5 "Little S.N.A.F.U"
1976 M151a2 "Kermit"

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rickf
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Re: Temp gauge explodes

Unread post by rickf » June 26th, 2017, 11:01 am

Live and learn. The coil is the most susceptible thin along with the electronic ignition and it sounds like both of them survived. Light bulbs would be next on the list so if you find that you have lights that don't work check the bulbs before anything else. It does not matter which side the cutoff is on as far as functionality, once the circuit is cut then the batteries are out of the loop and the electrical part of the truck is dead. The main reason for putting a cutout on the ground side is safety, there are usually a few more bare connections on the switch and any bare connection on a hot side is a short circuit danger. On the ground side it is nothing.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Temp gauge explodes

Unread post by 1943Willysgpw » June 26th, 2017, 11:06 am

Once the vehicle is started the Alternator is the source of electrical power. It uses the battery as a capacitor but the amperage still returns to the ground of the alternator. By disconnecting the positive with the kill switch, the circuit was incomplete and the voltage (pressure) pushing the amperage will spike and the amperage will flow where it finds a path. POW

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Re: Temp gauge explodes

Unread post by rickf » June 26th, 2017, 11:13 am

Good point, I was basically referencing which side for normal circumstances. Under normal circumstances the engine would not be running with the battery disconnected. That being said you can get away with doing that on old vehicle equipped with a DC generator but not with vehicles equipped with an alternator. Any more I just tell people it is bad practice altogether because voltmeters are so cheap nowadays there is no reason to check charging by pulling a cable. There are also very few vehicles out there with generators. the A1 had generator up til the last couple years when most went to the 60 amp alternator.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Horst
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Re: Temp gauge explodes

Unread post by Horst » June 26th, 2017, 11:55 am

a good kill switch has actually 6 poles and is on the positive side. One switch disconnects the battery, the second one grounds the now open plus wire via a resistor to ground (and saves the alternator doing that), the third disconnects the ignition to ensure that the engine is in fact turned off.

This is how kill switch should be installed on race cars, if not, they should not pass inspection. A little more work than just disconnecting the battery with a simple one. I have it on my 911...
Horst

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muttguru
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Re: Temp gauge explodes

Unread post by muttguru » June 26th, 2017, 6:07 pm

There's a very interesting writeup of problems that can arise when using kill-switches.
Have a look at:-

viewtopic.php?f=3&t=6169&p=50353&hilit=battery#p50353

Ken
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Always wanted - Details and pictures of M416 Trailer data plates & M151 data plates & body-tags for my research. Thanks!

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svramselaar
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Re: Temp gauge explodes

Unread post by svramselaar » June 27th, 2017, 5:23 am

hi

below the switch as horst say
http://www.racewareshop.com/contents/me ... 145205.jpg
if you use a little contact switch from it to switch the no 568 wire at a A2 you disconnect the alternator before the switch opens the battery connection

a alternator can get to 200 volts max without battery
a alternator gets his reference from the battery
the regulator works it lowers the voltage to the stator this will be less magnetic and the alternator voltage go down
the voltage difference between battery and alternator go down so also the load
the load tad you not used go not to ground
it is better to set the kill switch at the ground cable at the positive cable is also posseble

george

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Vzike
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Re: Temp gauge explodes

Unread post by Vzike » June 27th, 2017, 9:07 am

When I bought my Encore, it had a marine type kill switch mounted to the inside of the tool box. It killed the positive side of the battery. The bad news was it was mounted poorly, and shorted out the batteries when the vehicle was running. It took a while to find the problem. I fixed it by removing the switch completely.

Recently, both NEW Optima batteries in my Encore exploded. The cause was a faulty alternator. When I measured the output voltage, I got it varying at 28-30 VDC. I replaced it with another, and am now looking for a voltage regulator to repair the alternator I removed.

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Re: Temp gauge explodes

Unread post by rickf » June 27th, 2017, 8:26 pm

Vin, 30 volts is not that far out of range, did you try adjusting the regulator? There is a company down there in the south that has all the parts for those alternators, They manufacture them but I keep forgetting the name of the place. Get hold of Fil, I think he has dealt with them.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Temp gauge explodes

Unread post by svramselaar » June 28th, 2017, 3:19 am

hi

the factory below reed the text for the right type
http://www.southernautomotive.com/catal ... cts_id/101

george

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Re: Temp gauge explodes

Unread post by Flyingvan911 » June 28th, 2017, 3:10 pm

I didn't figure the gauges could explode like that. I'm glad you weren't hurt. They must have subcontracted their work to Takata.

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Re: Temp gauge explodes

Unread post by Vzike » June 28th, 2017, 6:25 pm

rickf wrote:Vin, 30 volts is not that far out of range, did you try adjusting the regulator? There is a company down there in the south that has all the parts for those alternators, They manufacture them but I keep forgetting the name of the place. Get hold of Fil, I think he has dealt with them.

Rick, After removing the back (voltage regulator), I found evidence of a failed components. The whole inside, including the back of the windings and the brushes were heavily covered with black char..... I think the regulator failed. Also, the three belts were burned half way through (but only in one place on each belt), as though the alternator locked up and the belts stopped, but the engine kept turning.

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