Strange problem with tach
 

Having a weird problem in my 6-speed swapped SVX. The tachometer reads low, sometimes around 2/3rds where it should be and more recently usually about half. (But it still seems to vary, even in the same driving session). Anyone ever experienced something similar?

I'm wondering if there could be a poor connection between the ECU and tachometer that's causing some of the pulses to be dropped? Either that or a problem in the circuitry of either the ECU or the tach causing some of the pulses to either not be sent, or not be received? Or maybe low voltage to some part of the tach causing the response to the pulses not to be as strong as it should?

I don't currently have a spare tach to swap in, so any ideas for how it might be fixed or what to look at would be very much appreciated. I have multimeter/soldering iron/etc, and a non-working tach in a spare gauge cluster that might be usable as parts.

Or, if anyone has a working one for cheap, that would be great, although it probably wouldn't ship very easily if removed from the gauge cluster, though I suppose I could send the rest of the gauge cluster back.

Thanks

Re: Strange problem with tach
 

You have the ECU tuner or similar software don't you? Check the tach on there to see the signal it's getting.

Re: Strange problem with tach
 

A couple of years ago, my speedometer failed. Soon after, the tach would struggle to go above 1500 RMP. Not being electronics literate, I replaced the gauge cluster with one with many less miles. All has been well since. I examined the printed circuit board but, could not detect any problems, except, the circuit board was warped. I recorded the difference in mileage and will always disclose the difference if the car is ever sold.
You are far better than me at this but, I took the old gauge cluster apart and could not see any easy way to replace the speedometer or tach.

Gene

Re: Strange problem with tach
 

What is it with these cars clusters and cold weather? Replaced my speedo over a year ago when it started reading off especially in the cold. With these recent cold snaps we've had, now the tach reads nothing to very little during driving. Is it the capacitors or resistors that don't like the cold or what? Lucky I still have the spare tach to replace the current one, but sucks that I have to pull it out again.

Re: Strange problem with tach
 

What did you do with the yellow (?) cable which gives the erev signal to the TCU? The tach get its signal from the same source. Maybe there's something there.....

You can check the signal with a normal scope - I did, for a different reason, though :eek:.

/T

Re: Strange problem with tach
 

Hooked up every thing the way it was as I pulled it out. It has something to do with outside temperature, when it's cold it reads low when it's above 60, it seems to read normal.

Re: Strange problem with tach
 

You may want to check the lubricating grease on the speed sensor itself. It tends to get thick with age and cold weather makes it worse.

Re: Strange problem with tach
 

Wouldn't that effect the speedo only? That part of the cluster is fine.

Re: Strange problem with tach
 

You're totally correct. My mistake