NB SE Tacho and Odo stopped working

[KevGoat]

Car is a 2004 NB8C SE. My Tacho and Odo suddenly stopped working today. The Tacho flicked very quickly down to zero and back to correct revs a few times, then it went off completely. At the same time, my odo went blank.

Pulled the instrument panel out and can't see anything on the circuit (looked with a magnifying glass).

Plugged it back in and all worked again, but then about a minute later the tacho & odo go off - tacho doing it's same flicker dance to zero.

If I just switch the ignition off & then start again, they are still not working. But if I unplug the instruments, plug them back in and start the car, the instruments go through the same routine - for about a minute all fine, then tacho needle flickering a few times quickly down to zero and back to revs then both the tacho & odo go off.

Tried searching the US threads and here, but couldn't find much.

It got too dark to carry on, so I bought the panel inside and spent ages checking all the tracks etc to see if any breaks or anything that look wrong, but found nothing.

Now, the only thing I did notice the last couple of times I tried it, was a clicking noise in the engine bay at the same time as the tacho & odo go off, as if a solenoid had switched.

Thought before I get back to it tomorrow, I'd see if anyone has any ideas? ...

[JBT]

the last couple of times I tried it, was a clicking noise in the engine bay at the same time as the tacho & odo go off, as if a solenoid had switched.

A relay failing or bad connection at a relay? Is here a relay that has an instrument connection/function?

[KevGoat]

That's what I'm wondering.

One thing I did find with searching was to check all the earth contacts, so I'll be trying to find as many of those tomorrow.

The way it happens is almost as if something is failing as it warms up and expands.

The clicking sound may or may not have any bearing, but it happened a couple of times exactly as something made a sound under the bonnet. Unfortunately I ran out of daylight.

[Rolley]

Out of curiosity what is your alternator output?
A dying Alt can show up first with the tach dropping to zero.

[KevGoat]

When I start the car the volt gauge is showing around 15v.

I had the instrument panel inside last night and went over it carefully, can't see any problems.

Plugged it back in this morning and now the tacho & odo don't start working at all.

Plugged in my OBD reader and checked for any error codes and none.

Engine starts, idles and revs fine.

Disconnected the battery for a little while and didn't make any difference.

Checked the fuse box and all fuses are ok. There's a fuse box under the bonnet, but not sure how to check those, but they look ok.

Tried every plug I could find under the dash and under the bonnet to see if anything loose and all seems secure, no frayed or loose wires.

Just about to go back out and check as many earths as I can find, but I would have thought there'd be other issues than this.

It's probably going to be something real simple, but starting to run out of ideas ...

[KevGoat]

Am going to get things back together enough to go for a drive - want to check if I have any speedo! Just had a thought that this may be something to do with the speedo sensor issue???

"I'll be back ..."

[KevGoat]

OK ...

Moved it on the drive and no speedo either! Need to check the sensor on the gearbox.

IIRC someone on here did a good fix by taking the sensor apart and re-soldering.

Time to Google .... I don't even know where it is! ... bet I have to take half the underside apart ...

Hopefully back later with some good news ...

[Nevyn72]

That was Roadrunner, see this post.....

viewtopic.php?p=786092#p786092

It doesn't seem to match your situation exactly but worth checking out.

[KevGoat]

Thanks Nevyn ... I knew there was one somewhere. I found a good write up on RevLimiter.Net as well.

Not sure that this sensor wouldn't just take out the speedo though, not the tacho & odo. Still seems more cluster related to me, but I'll jack the car up & take a look anyway.

[93_Clubman]

Tacho gets its signal from the ECU on the NB, so might be worth checking the ECU: viewtopic.php?f=81&t=52554&p=662156&hilit=tacho#p662156

tachometer drops to zero immediately even while the engine is still turning.

The American's problem seemed to be a polyfuse in the Haltech ECU, although another issue raised its head later:
viewtopic.php?f=29&t=67030&p=832614&hilit=tach%2A#p832614

[KevGoat]

So I'm now finding if I unplug the left plug from the rear of the instrument panel - looking at it in dash - and then plug that back in, it temporarily resets every thing. Turn ignition on and leave it on for a couple of minutes and the odo goes off (obviously no tacho as engine off). So this is happening even with the engine off and everything sitting still. Have also noticed the seat belt warning buzzer doesn't work when the instruments have switched themselves off.

93_clubman - thanks. Might leave that to the experts though. Not sure what I'd be looking at and don't want to make things worse.

I'm thinking maybe I should source another instrument panel to plug in and try.

Otherwise ... auto electricion

[KevGoat]

I've just noticed that when leaving the ignition on, after about 15 seconds the CEL flashes 7 times then goes back to solid. Never noticed this before. Plugged in my OBDLink but no errors showing.

[Tony]

I vaguely recall reading something about CEL flashing codes on the Mazda-speed.com forum.

It may be worth having a search over there.

[KevGoat]

Thanks Tony. I had quickly been trying to find something about flashing codes, but only came up with the OBD type codes. Will try later on. Time to get some other stuff done

[Tony]

Not sure if this will help, but may be a starting point...

http://www.mazda-speed.com/forum2/index.php/topic,13896.0.html