Mouse2k4

The other day my tachometer failed and it was crazy cold out... about 9 minutes down the road, it came back on...

Another day my tachometer worked right off the bat and it was warm outside. Stayed on all day.

Another day my tach work when it was warm out and I parked it while I was at work and after the sun went down and it got cold it wouldnt work at start up until about 9 minutes down to road again...


So I was assuming it wasnt working because it was so damn cold outside so I went and grabbed another to see if maybe it got weak and just stopped working or something and swapped the new one in and it doesnt work at all now...

Cleared off the ground points on the shock tower but still didnt work. When it had no ground at all it nudged the needle about a millimeter but thats all I could get from it....

Any ideas?



Also note that it runs either way but slightly better when I have tach.

Mouse2k4

Just ran a jumper wire from the leading coil to the single open connector that doesnt connect to anything and the tach was bouncing. the integrity of the wire looks fine.... Will have to pull it out and maybe clean off the connector but I dont believe it would be causing this.

AGreen

iTrader: (11)

Try swapping the trailing coil. That's where the tach gets its signal.

Mouse2k4

Already did. Didn't make a difference which I used.

Mouse2k4

Also more notes: I recently upgraded to an S5 alternator. (The cars an S4) and I put an optima yellow top in it.

jlee916

i'm gonna have to try swapping the trailing coil myself tomorrow. my tach is also messed up very similar to yours, but i have an s5.

Mouse2k4

Let me know how that works out for you. I gotta find out if the tach I have and the used tach I bought are both defective or if its a ground issue or something.

satch

iTrader: (1)

Did you turn the key to start to see if the needle jumped and that's all or did you actually start the car up and while running the tach needle just bounced?

Mouse2k4

When I started it the tach needle just bounced real roughly between 1k and 2k

jlee916

lol **** you're talking about tach and i confused myself with speedometer. yeah my problem is the speedometer not working well. will changing the coil help my issues?

satch

iTrader: (1)

No it will not as it is unrelated to your issue.

Mouse2k4

Not if you have an s4 or an s5 its a cable that runs directly to the trans that has a pin in it that spins it

Mouse2k4

Drove the car about 10 minutes today and still nothing from the needle... was thinking about taking a jumper wire and running it straight from the yellow/blue wire to the pin on the back of the cluster.

Mouse2k4

Im pretty sure the right side is the true ground but they both seem like they would be grounds? Didnt have sand paper or a wire brush but I took a flat head and scraped as much corrosion and paint off of the contact areas as I could and idk I get more reaction without it grounded. Fully mounted the needle doesnt move at all and when I unmount it from the grounds I get a little nudge from the needle.

Mouse2k4

Problem Solved?????
Drove the car with the 'newer' coil in it and still had no tachometer. decided to clean up all the grounds of the 'old' coil with a drill and a wire brush attachment. anywhere that looked like it might have something to do with the grounding operation(even inside under the back lid and underneath where the other support is screwed into the bottom of the coils. I also took the wire brush to the threads and washers of all the screws because every little bit helps and really just went HAM at wirebrushing under all the ground points involved and it appears to have fixed the problem.

Will update again in a week to see if any problems occur.

rxmiles

iTrader: (11)

Please, do update. I am having the exact same issue again. It appears that most of the time, when cold the tach won't work. After driving for some time it will kick in. I had this issue when I bought the car. I tried almost everything, from swapping coils to cleaning major grounds. I finally just replaced the tach itself in the original gauge cluster, and it worked great for a while until the problem began once again. I will be trying to disassemble the coils like you dis to clean the wiring, but won't sand down the paint. I will try to make better grounds by wiring instead.

Mouse2k4

Okay so little update.... The Tach worked fine today until the sun went down and it got cold out. I got in the car and had 0 tach so started driving and as soon as I pulled out of the lot it came on... ***** bothering me.

sc0rp7

iTrader: (3)

I have a s5 with the exact same problem... I was gonna try my ground block on the rear of the shock tower. But now I wonder if that will have any effect... Good luck and I will update my situation as well.

rxmiles

iTrader: (11)

There has to be something.... This is seems to be a problem the S5's have but yet no concrete solution.

Mouse2k4

Lol mines an s4 so I guess its all FCS lol

AGreen

iTrader: (11)

Try hooking up an aftermarket tach to where the stock one gets its signal. If the aftermarket one works and the dash tach does not, you have solved it. I am having a similar issue with my truck. Sometimes the speedometer works, other times I get tickets. I have verified it's a cluster issue.

Mouse2k4

Well I would believe its the cluster itself because the car tends to run roughly while I have this problem.

RotaryEvolution

iTrader: (30)

fouled trailing spark plugs will also exhibit the same symptoms of a failing trailing coil.

Mouse2k4

Okay so what you're telling me is if I have bad spark plugs I could lose tachometer?... if this is the case it really makes sense why the cold affects it so much and why it would require warming up to come back online

Mouse2k4

Was warm out today and the cars tach worked fine all day.