HMMWV Tachometer Installation

[Haasino]

Does anyone have, or could they point me in the direction to find, the diagrams for hooking up the newer-model tachometer in a Humvee? I'm referring to the model that mounts up next to the wiper motor, not on the doghouse... it's already been installed... but was apparently never hooked up.

Thanks!

 

[BLK HMMWV]

I just hooked mine up a few weeks ago let me see if I still have the install sheet laying around. There are a total of 5 wires coming off of the wiring loom from the tach (3) drop off behind the dash and hook up to the fuel gauge wiring (they may or may not be hooked up already) and the other (2) enter into the engine compartment from a hole that needs to be drilled behind the dash. They hook up to a terminal under the small metal cover on the top of the alternator. You will need to acquire a gromett and a weatherproof connector (male end if I remember correctly)
I'll hunt around today and see if I can find it.
If the only two that are not hooked up are the two in your picture then I can tell you were those go already.
What size alternator do you have ? 60 Amp?
if so you will see a small metal cover on the top of the alternator with some wiring coming out from it (1) large wire and (1) small wire about the size of the ones in your picture. Basically the existing small wire with a ring terminal gets removed from the alternator and is replaced with the new wire with the ring teminal, the remaining new wire should have a female weather proof connector end on it. The old wire that you removed from the original needs to have the ring terminal cut off and a male end installed . it will then plug into the new female connector.

Confused I would be.
It's pretty straight forward but It would be better if I gave you all the wiring #'s . And I need to find the paperwork for that or pull the HMMWV out and lift the hood
BH

 

[Haasino]

I just hooked mine up a few weeks ago let me see if I still have the install sheet laying around. There are a total of 5 wires coming off of the wiring loom from the tach (3) drop off behind the dash and hook up to the fuel gauge wiring (they may or may not be hooked up already) and the other (2) enter into the engine compartment from a hole that needs to be drilled behind the dash. They hook up to a terminal under the small metal cover on the top of the alternator. You will need to acquire a gromett and a weatherproof connector (male end if I remember correctly)
I'll hunt around today and see if I can find it.
If the only two that are not hooked up are the two in your picture then I can tell you were those go already.
What size alternator do you have ? 60 Amp?
if so you will see a small metal cover on the top of the alternator with some wiring coming out from it (1) large wire and (1) small wire about the size of the ones in your picture. Basically the existing small wire with a ring terminal gets removed from the alternator and is replaced with the new wire with the ring teminal, the remaining new wire should have a female weather proof connector end on it. The old wire that you removed from the original needs to have the ring terminal cut off and a male end installed . it will then plug into the new female connector.

Confused I would be.
It's pretty straight forward but It would be better if I gave you all the wiring #'s . And I need to find the paperwork for that or pull the HMMWV out and lift the hood
BH

Yeah, a little confused, heh... either the paperwork or photos of the 5 wires installed should be all I need. I'm not sure if the other (3) wires are hooked up to the fuel gauge wiring, but I'm hoping they are... the original alternator that was installed in this Humvee was complete garbage, so I'm guessing that's why the guy strung the (2) wires up to the alternator, but didn't actually connect them.

Right now, it has a new 60amp alternator installed... I've attached 2 photos of it below. I assume the metal cover you're talking about is the one with the yellow warning label on it?

Thanks for the help!

 

[BLK HMMWV]

Yes your correct the wire is under the cover with the yellow label.
I looked for the install papers but I must have chucked them.

Basically the small wire under the yellow cover is removed and the new wire with the ring terminal is installed in it's place. Then the ring terminal is removed from the old wire and a male weather proof connector is installed on the end of the wire. It then plugs into the female weather proof cover that is part of the new tach wiring.

Thats it. As long as the other wires are hooked up behind your instrument panel.

BH

 

[Augi]

Did you ever get the tach working? I just installed one in my humvee but the tach does not register. I am getting +24V at the tach connector on the appropriate pin and ground on the appropriate pin. I don't know what the signal is supposed to look like though.

Also, where does the wire lead to that you cut the ring terminal off of and crimp the new connector to?

Thanks,
Augi

 

[BLK HMMWV]

Hi Augi
See the post right before yours.
It attaches under to a screw on top of your Alternator . The one with the Yellow Label on it.
Were in So-Cal are you?

BH

 

[Augi]

Yes I read that post. I also have the directions from the kit, but they assume you have a dual voltage alternator with a voltage regulator. Do you know what the signal is supposed to look like coming off the alternator? I could look at it with a scope.

Under the cover there are six wires. Three come from the alternator phases and are soldered to posts. The fourth is soldered to a fourth post and is terminated with a male connector identical to the one that I crimped on to the signal wire (the wire this connects to runs into the vehicle harness as part of the same bundle as the +24v wire and the signal wire). The fifth wire is the signal wire with the small yellow ring terminal and the sixth wire is the large black ring terminal which I presume is the +24DC output. There is also a ground strap that connects to the frame outside of the little cover.

I replaced the fifth wire with the wire from the tach harness, crimped the new end to the fifth wire and hooked it into the tach harness. It was held onto a stud with a nylock nut.

But the tach needle still does not move.

I am in San Luis Obispo.

 

[Augi]

So I figured out the problem: My gauge is DOA.

I took a look at the AC signal coming off of the alternator with a scope and it looks fine, both at the stud on the alternator and at the cannon plug on the windshield.

I had one of the electrical engineers at work hook the gauge up to a signal generator and it would not respond to any of a variety of AC signal frequencies @ 15V (which is what the alternator is outputting from a single phase).

SOOOOOO I found the number for the gauge manufacturer and I'll see if they will give me an RMA for it tomorrow

Augi

 

[jwaller]

they are on ebay all the time. they are usually listed for the M35a3. same gauge.

 

[BLK HMMWV]

ooops

 

[Retiredwarhorses]

The truck in this thread is one of the trucks I installed a Tach in with a 60amp gen....

 

[Jaaudio]

Good afternoon, all. Will someone point me in the direction of the mounting bracket shown in this thread? I'd like to mount my tach to the a-pillar, too. Muchas gracias...

 

[Jaaudio]

Does anyone have, or could they point me in the direction to find, the diagrams for hooking up the newer-model tachometer in a Humvee? I'm referring to the model that mounts up next to the wiper motor, not on the doghouse... it's already been installed... but was apparently never hooked up.

Thanks!

Will you tell me where you got the mounting bracket? Also, will you tell me which sun visors you have?

Blessings,
Jonathan D. Pollard