tach dash unit fix?

[chris canary]

hello to everyone,
i have just finished most of my maintenance work on my recently bought rd28t without major problems, the only thing that won't work is the tachometer (sometimes it works, than it's jumping around or stays dead). i've narrowed it down to the actual tach mounted in the dash. altough i don't have an oscilloscope funktion on my multimeter i am pretty sure that the error is hidden there, because all the electrical connections are fine, all the ground connections are cleaned up, the resistance of the rpm sensor and the alt.voltage output before and after the ecu are as sugessted in the manual.
if anyone could give me a hint what to look for, or how to identify the error , once i've taken the tach out the dash unit i would really apreciate that.
saludos
chris

[mudnut]

Hello, and welcome to the forum.

What model is your Patrol?. If it is a GQ / Y60? If so it is easy to remove the tacho unit. Since you have said you have traced the problem back to the tacho gauge, can you swap it with another unit that you know works? That will confirm that it is a wiring loom or sender problem or not.

If you cant do that, remove the gauge and visually inspect the circuit board. Sometimes the soldering can be affected by vibration or corrosion.

[chris canary]

hi,
thanx for the answer!
it is an y 60 that i've got. already taken the gauge unit out, and will check the soldering ,since it's not that easy to get an affordable unit to swap around here,
greets
chris

[dom14]

hi,
thanx for the answer!
it is an y 60 that i've got. already taken the gauge unit out, and will check the soldering ,since it's not that easy to get an affordable unit to swap around here,
greets
chris

It's usually the corrosion or dust weakening the contacts. Give it a bit of a clean with a tooth brush and some carby cleaner spray, etc.
It's a pretty common problem with GQ dashboard gauge unit.

[chris canary]

well, i got the gauge disassambled to the smallest possible unit, cleaned with contact cleaner , put it back in and it worked fine for a couple of days, then it just started doing the funky chicken again. i guess i'll just change it to an aftermarket gauge that is able to read pulses.

[mudnut]

Since you have found it is the gauge, have a go at soldering all the joints you can get to. If you aren't confident, let someone else do it. The trick is to clamp a heat sink on the leg of the component, and be quick when applying the iron. A pair of small needle nose pliers with rubber bands to make them clamp the leg also does the job too.

[PeeBee]

well, i got the gauge disassambled to the smallest possible unit, cleaned with contact cleaner , put it back in and it worked fine for a couple of days, then it just started doing the funky chicken again. i guess i'll just change it to an aftermarket gauge that is able to read pulses.

I have just lived thru this same thing with my GQTD28 tacho going intermittently mental. I sent the vehicle to WA for the engine transplant and when the 'thing' left Melb, it was working. Anyway, it died over there and a second tacho was put in - this lasted 24hrs and it died. The diagnosed root cause was 'voltage spike'. Anyway, a third tacho was sourced and installed with some 'fancy wiring' and its supposedly running stable and OK. I am none the wiser, not at root cause and frustrated, plus a lot lighter in the pocket - hope you don't end down this track.

[dom14]

I have just lived thru this same thing with my GQTD28 tacho going intermittently mental. I sent the vehicle to WA for the engine transplant and when the 'thing' left Melb, it was working. Anyway, it died over there and a second tacho was put in - this lasted 24hrs and it died. The diagnosed root cause was 'voltage spike'. Anyway, a third tacho was sourced and installed with some 'fancy wiring' and its supposedly running stable and OK. I am none the wiser, not at root cause and frustrated, plus a lot lighter in the pocket - hope you don't end down this track.

Hi Phil,
Do you have more information on that "killer voltage spike", the origin of the spike, etc etc??!!
It would be great to know.
Cheers
Dom

[PeeBee]

Hi Phil,
Do you have more information on that "killer voltage spike", the origin of the spike, etc etc??!!
It would be great to know.
Cheers
Dom

Dom,
I spoke with Greg at Brunswick and he was at a loss as to whats causing it, needless to say they think they have 'gone around it', which is kind of a fix i guess. I will get full details of the magic box they installed as part of the fix and will follow up later with him. Vehicle has left Perth, is on train to Adelaide and due there on 20th - so getting closer!!!
Phil

[dom14]

Dom,
I spoke with Greg at Brunswick and he was at a loss as to whats causing it, needless to say they think they have 'gone around it', which is kind of a fix i guess. I will get full details of the magic box they installed as part of the fix and will follow up later with him. Vehicle has left Perth, is on train to Adelaide and due there on 20th - so getting closer!!!
Phil

Hey Phil,
If it happens again(which I seriously doubt), I would suspect some electrical short circuit somewhere in the wiring.
Some of those goblins are no easy to spot, but magically fixes itself when you replace the wiring, as is the case with my fuel pump
issues.
Cheers

P.S. Post some photos of the rig when you get it. :)

[PeeBee]

Hey Phil,
If it happens again(which I seriously doubt), I would suspect some electrical short circuit somewhere in the wiring.
Some of those goblins are no easy to spot, but magically fixes itself when you replace the wiring, as is the case with my fuel pump
issues.
Cheers

P.S. Post some photos of the rig when you get it. :)

Dom,
I will be interested to see if its just the tacho or a board as well that was replaced as I know BD had to buy a complete dash the first time. Vehicle is due into Adelaide tomorrow then road to home - maybe by mid next week.