hmmwv tachometer installation

hmmwv1 · Apr 28, 2016

since i searched the internet for almost 4 hours and could not find complete instructions on installing this tachometer i thought i would post my install
the tach is a military issue tach made by dixson for the hmmwv.it is a 3500 rpm with an hour meter and light and does not have a pre wired plug(i bought it off the internet) made my own mount too
part number is 6680-01-474-0384
there are 5 wires to hook up
first is key on power- spliced off the power feed on fuel gauge
second is ground- connected to back of instrument gauges gound
third is light-spliced off of instrument gauge light feed
the next 2 wires are signal feed wires for the pulses,the tach drive in the rear of motor is where they hook too,it does not matter which goes where,they are just pulses and work the same if reversed
hour meter count engine running time
it would not work hooked up to the alternator a/c output,read 2900rpm at idle

hope this helps someone
.

hummer4x4guy · Apr 28, 2016

Thanks for the post hmmwv1

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Retiredwarhorses · Apr 28, 2016

Good work....where is the 2nd red wire going? I see the 24v feed to the gauge, the ground to a gauge....is that the one that goes to the inst gauge lamp power?

Recovry4x4 · Apr 28, 2016

Outstanding. Going to try this type of install on a CUCV.

rookie · Apr 28, 2016

Where does the hour meter Hook up to

TNriverjet · Apr 28, 2016

Very nice work hmmwv1! I have been wondering how these hook up. Great work on the mount too.

FYI I'm picking up an auction lot of GL parts soon that contains a bunch of these tachs. I'll have them listed in the parts FS forum next week. Anyone needing one can PM me.

hmmwv1 · Apr 29, 2016

Retiredwarhorses said:
Good work....where is the 2nd red wire going? I see the 24v feed to the gauge, the ground to a gauge....is that the one that goes to the inst gauge lamp power?

yes the 2nd red wire is for lights,i connected a brown to it and went to gauge cluster

hmmwv1 · Apr 29, 2016

TNriverjet said:
Very nice work hmmwv1! I have been wondering how these hook up. Great work on the mount too.

FYI I'm picking up an auction lot of GL parts soon that contains a bunch of these tachs. I'll have them listed in the parts FS forum next week. Anyone needing one can PM me.

did you buy the ones that was on gl about 2 weeks ago?

hmmwv1 · Apr 29, 2016

rookie said:
Where does the hour meter Hook up to

hour meter starts working when it gets a tach pulse,only runs when engine is running

Retiredwarhorses · Apr 29, 2016

I put the same in the m1097 today...took about 2hrs but worked like a charm...thanks brother.
just so happens I have had one of those tach's for years and found it looking for something else...I had the A-pillar bracket in another box. This tach was part of the complete kit for an ambulance on the dog house with the Ste/ice harness as well...

darr3239 · Apr 29, 2016

Why did they put these on certain models and not on all?

Retiredwarhorses · Apr 29, 2016

darr3239 said:
Why did they put these on certain models and not on all?

i don't think I ever saw a tach in a HMMWV.....not even today, and I get more then my fair share going through my section at the base....like every month. I believe they were for the ambulance.
of a truck had a tach, you would see the tell tail sign of where it was mounted...A-pillar rivnuts to the left of the wiper motor, and holes all over the left side of the engine cover...but you don't see it, not even on the Gp trucks.

rookie · Apr 29, 2016

Ok thanks on the hour meter. Good write up

DainGerous · Apr 29, 2016

Found a schematic AM General tach setup if anyone wanted.
http://www.galuba.org/hummer/Tachometer-A2.pdf

darr3239 · Apr 29, 2016

I guess I don't understand why they would need one in an ambulance as opposed to the other versions.

Recovry4x4 · Apr 29, 2016

darr3239 said:
I guess I don't understand why they would need one in an ambulance as opposed to the other versions.

Probably more about the hour meter since idling is likely.

TNriverjet · Apr 30, 2016

Recovry4x4 said:
Probably more about the hour meter since idling is likely.

Was there a need to idle the engine up while parked to provide adequate power for certain accessories associated with the ambulance? I could see a tach and a throttle lock being used for that purpose.

darr3239 · Apr 30, 2016

That makes sense.

Recovry4x4 · Apr 30, 2016

I'm not familiar with.the HMMWV or its ambulance variant. My CUCV ambulance has patient compartment heat and A/C and NBC equipment as well. Assuming the HMMWV has the same equipment, an hour meter would be very beneficial for determining service intervals and the tach for determining off idle RPM for running the equipment in the PT compartment.

hummer4x4guy · Apr 30, 2016

Tach also good when operating a winch.

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hmmwv tachometer installation

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