tach issues.

[blown84]

so my 84 has a factory tach for its 6.9 (or at least the cluster ) but it doesnt work. if you hit the dash, it wiggles a little bit, then dies and goes back to zero. on FTE, i was pointed to a conductive glue on the back of it, that needed to be scraped off. SO, i took the cluster out, took the tach out of it, and there was no glue. so i cleaned up all the connections and the wirin harness and put it back together. same story. i HATE electrical issues and diagnosin them, and beins im kinda new to the world of diesel maintenance, i have no idea what im lookin for, or where its at to fix it. i got a cluster out of a gasser the other day to plug it in and see if it was an issue with the gauge, or somethin else, but havent had a chance to try it out yet. maybe yall have had this issue and/or can point me in the right direction. thanks.

P.S.- does anyone know where i can get some blue LED lights for the gauge cluster??

 

[rhkcommander]

I might have some blues ill check for ya

IIRC you can test the tach sensor with the engine running to see if it works by: getting a multimeter out and set it to AC and should see about 40 IIRC. But i might be wrong.

 

[Matrix37495]

I dont know about the tach, but as far as the lights...don't waste your money...

I was going to put some different color lights in until i saw the green glow is from white lights shining through a green plastic piece thats part of the cluster..... So unless you take it all apart and remove that, you would barely be able to see your gauges at night... :/

 

[blown84]

well, a green filter means it only lets blue and yellow light through (green), so if it should let the blue light though. however, i do plan on removin the filter anyways. i also plan on usin model paint to paint the gauges white with blue numbers and needles.

rhkcommander, if you have some, that would be VERY much appreciated as i have no idea where to find em.

where is the tach sensor on these trucks? beyond the gauge its self, i have no idea what im lookin for.

 

[93f250idi]

tach sensor is located by the oil fill neck. i think its a 1 inch nut with 2 wires coming out of it

 

[Knuckledragger]

Tach sensor is screwed into the top of the IP gear housing, behind the oil fill neck. 1 inch hex, two wires running back toward the alternator.

Don't bother trying the gasser tach, they apparently run on different signals and are not compatible with a diesel setup.

 

[blown84]

perplexed: no such connection on IP gear housin. the first time i started it up the tach jumped all the way to 4500 rpm and got stuck. took it apart, put it back to zero, and it would wiggle when you hit the dash. so its wired into SOMETHIN...

 

[SparkandFire]

That tach is a "magnetic reluctance type gauge" which means it has a stationary magnetic core with windings wound around it, and a rotor sandwiched between the two that drives the pointer.

Could be that when you whack the dash it's throwing the magnetic fields around like crazy inside the meter, causing it to go haywire and look like it's working.

If you don't have a sensor on the IP gear cover I am not sure there is any other way to get the signal to the factory tach?

 

[hesutton]

perplexed: no such connection on IP gear housin.

No sender, no functional tach. Is there a plug of some kind in the housing on the drivers side? There should be, otherwise oil would go everywhere when you run the engine.

Heath

 

[blown84]

so i have a tach, with no tach?

 

[blown84]

no holes, no plugs, no sensor...

 

[hesutton]

no holes, no plugs, no sensor...

When you said you had an '84 I was concerned. Tach were not a diesel option until '85 IIRC. You may have a cluster from a later year, or someone put a tach into your cluster? If the cluster is from a '85-'86 IDI, then all you need to do is get a IP gear cover that has a prevision for a tach sender and the sender itself. Swap them out and wire it up. (warning..... if you do this, DO NOT REMOVE, MOVE, OR EVEN LOOK AT THE IP GEAR FUNNY.... getting that gear out of time with the cam gear is a headache you don't want).

Here are some photos that may help to hook up a factory tach without the tach circut board on the instrument cluster:

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Heath

 

[blown84]

thanks a bunch heath. now that you point out that pic, i remember that the contacts on the male harness for the tach were not there. i thought they were for somethin else, but they are right where that pic says the contacts should be. the entire cluster is for a tach, but i guess the trucks not.

do i have to remove the IP to swap the housin out, or just un-bolt it?

 

[hesutton]

do i have to remove the IP to swap the housin out, or just un-bolt it?

You'll have to remove the IP. It may be possible to move the IP out of the gear and housing far enough to pull the housing off, but it will be a struggle and may cause you to move the IP gear out of time. I'd just pull the IP entirely, then swap the gear housing.

Heath

 

[blown84]

well, if that is the case, i think i will wait til i get a moose pump, so im not just repeatin processes...