M35A3 RPM Gauge Not Working?

[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?

 

[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.

 

[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.

 

[TP500]

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]

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

 

[Tap5430]

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]

with these part numbers one can find all the information wanted
Could look in the TM too

Tachometer (Electronic) For M35A3, 12448944 / EX2458

Tachometer with hour meter, 0-3000 RPM, electronic pulse input and STE/ICE-R output signal. Built in LED back light. Requires 24-28 volts DC operating voltage. Calibrated for use with the 134 tooth ring gear as used in the M35A3 truck (Cat 3116 engine). <br> P/N 12448944, alternate numbers...

www.eriksmilitarysurplus.com

https://www.parttarget.com/6680-01-415-4025_6680014154025_12448944.html/-9a362b83-daf7-4963-ac9e-799a0d5c93c9?searchtext=12448944&searchoption=sku&originalsearchtext=12448944

Tachometer question on my M35A3 ?

my tac just stopped working and not only I like all the gauges to work but the tac has the hour meter on it and I need that ....I have checked the wires at the alternator but they all look good ...so now im going to check the wires behind the tac ....but it would be nice to hear from y'all on...

www.steelsoldiers.com

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

 

[HDN]

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