M35A3 RPM Gauge Not Working?

Dustyh

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I have a M35A3 that the RPM gauge is not working on, any suggestions on were to start to try and find the problem. Thanks
 

Dustyh

New member
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Location
McAdoo, TX
I did not unsrew it yet but not sure that it has a shaft running to it like the speed odometer. It has a buddle of about 6 wires that screw into the back of it. It will jump when you trun the master switch on but will not work with increase in rpms. I will unsrew it next chance I get and see. Also the low air light and alarm does not work, any suggestions there. Cant find any loose wires behind dash.
 

armytruck63

Active member
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Redlands, CA
Check the "spider", the common ground point for all of the gages. If it is loose or has a dirty contact screw, all of the gages will be intermittent or not working at all.

You "should" have a mechanical tachometer with a drive cable. The only electrical part is the instrument light bulb that lights it up when the dase lights are turned on.

Maybe there is an electronic tach that I am not aware of.

Good luck.
 

Wolf.Dose

Active member
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Location
Boehl-Iggelheim, Germany
Electric tachs are only in the A3 versions in Europe. However, they are povered by the standard mechanical cable. To my experience most the times the mech cabel is overbend somewere and the protective rubber hose is craced due to age. It is difficult to see, however, below it, the cable is rusted to the housing. So check the turning of the tach cabel on the tach side with the engine cranking. If the joint does not move, replace the cable. That the drive fails is almost unknown.
Wolf
 

PowerstrokeNC

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Location
Greensboro, NC
I have exactly the same problem on my A3, there is definitely no drive cable on mine just a pin plug. I bought a brand new gauge and plugged it in and nothing so I don't think it is the gauge, it must be the sender on the engine, anybody know anything about this?
 

AceHigh

Well-known member
2,175
27
48
Location
Princeton WV Lake City FL
Welcome to the no-tach club. I have a new one on my desk that was advertised as a A3 tach but it is not. It eaither pegs the needle or won't move. I have researched it and it seems to be a HUMMWV tach. Still looking for an A3 tach.

The sender is a magnetic pickup on the transmission bell housing. It is easiest reached by removing the metal panels in the cab and reaching thru. You loosen the lock nut and tighten till it bottoms out, back it off 1/4 turn.

If you find the tach let me know! BTW there are just two wires from the sender to the tach.
 

TP500

New member
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Location
Salt Lake City, Utah
Am new to the M35A3 club, My Tach does not work except if I rev the engine or hit about 45mph it will move a little, Tried another tach the same thing they are not cable driven. My fuel gauge jumps around and my oil pressure gauge pegs the needle (a wire grounded I am pretty sure) I am going to try looking at the grounds and look at the tach sensor. Has anyone figured anything out on this ? maybe save me some time. If I find anything I will post it.
 

TP500

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Location
Salt Lake City, Utah
Okay, I did try adjusting the tachometer pickup or sensor it then tried to work but not until 1300 or so RPM's, So with some of the info here on Steel Soldiers I came up with a part number that worked Cat# 318-1181 It is a little longer and has a different plug. I spliced in the old plug installed it, Now my tachometer works great, It is not a cheap part $120.00....But I now have a reliable Tachometer
 
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Tap5430

New member
Welcome to the no-tach club. I have a new one on my desk that was advertised as a A3 tach but it is not. It eaither pegs the needle or won't move. I have researched it and it seems to be a HUMMWV tach. Still looking for an A3 tach.

The sender is a magnetic pickup on the transmission bell housing. It is easiest reached by removing the metal panels in the cab and reaching thru. You loosen the lock nut and tighten till it bottoms out, back it off 1/4 turn.

If you find the tach let me know! BTW there are just two wires from the sender to the tach.
Thanks for information, been hunting this thread for days. New members take note the details in A2 A3 designation!
 

frank8003

Well-known member
Steel Soldiers Supporter
In Memorial
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with these part numbers one can find all the information wanted
Could look in the TM too




One could go look at TM 9-2320-386-24P work packages 0057 00 and 0066 00 and 0071 00
 

HDN

Well-known member
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Location
Finger Lakes Region, NY
The tach on my truck has been mostly non-functional this year after having worked all last year. I might pull the doghouse and adjust the tach sensor before running the troubleshooting procedure to see if that fixes the issue. I haven't been under the doghouse yet anyway.

It's a good thing I've run the truck enough now to know what the motor sounds like at what speed :)
 
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