Dustyh

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

800summit

unscrew it from the back of the tach ,start the engine see if shaft spins, go from there

Dustyh

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

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

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

5_TON_TOMATOE

PowerstrokeNC

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?

__________________
M35A3
M923A1
Trolling GL for.....

AceHigh

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.

__________________
This space intentionally left blank.

AceHigh

Oh, forgot to add: I checked at our local Cat dealer and apparently it is not cat stuff. They pretty much laughed at me.

__________________
This space intentionally left blank.