2002 Tach not working properly

[sstocker31]

New to me van....very low milage 101,000 KM. The tach is the only thing on it that doesn't work properly. At idle the tach doesn't move at all, but if you rev the engine up to a steady higher RPM it will move the needle, although it's not registering the correct Rpm.
I saw the posts on the solder joints at the back of the instrument cluster, but since everything else works in the instrument cluster I'm not sure that would be the cause.

Any ideas where to start looking?

[RIP]

The cluster solder joint issue applies to 3rd generation 1996-2000 vans.

Try a cluster calibration. Hold the trip reset knob in then turn the key to on/run. Within a few seconds the gauges/lights should start cycling. When the odometer says SOF release the knob.

[sstocker31]

Originally Posted by RIP

The cluster solder joint issue applies to 3rd generation 1996-2000 vans.

Try a cluster calibration. Hold the trip reset knob in then turn the key to on/run. Within a few seconds the gauges/lights should start cycling. When the odometer says SOF release the knob.

OK....I didn't know that the solder joint thing didn't apply to my year van...thanks for that. I did do the cluster calibration before I posted this thread, and the tach did a bunch of movements. I'm not sure what it's supposed to do, but it looked like it knew what it was doing....at the end I think it said it was done. No changes though, tach still isn't working properly.

How can I check the connections starting at the engine. Im not sure where to start checking. I also have an aftermarket tach I can use as a testing tool.

thanks for any advise....,

[sstocker31]

OK just to keep you posted on progress, I pulled both battery terminals and cleaned them throughly, then tested it to see if that worked....it didn't. Next I removed the connector to the coil looking for corrosion, there wasn't any, so I reassembled it and tested, with no postive results. Next I removed the instrument cluster looking for poor connections, I found a little corrosion on one pin, cleaned that up, tested it, and no dice...still not working. Next I took the instrument cluster completely apart, and looked for poor connections or some electrical component that is in obvious distress....didn't really find anything, so I assembled it back together, tested it, still no progress.

I'm going to go get a spare coil pack at the junkyard and try that....I'll keep you posted

[RIP]

Wiring diagram shows no direct tach input to the cluster so I would have to assume it comes in over the PCI data bus wire at pin #9 on the cluster. Pretty sure bet if there was a problem there you see much more than an erratic tach. From that point it's a guessing game as to the actual source except for a thread I read long ago that the tach signal source is the crankshaft sensor. Trouble is that's the one and only time I read it. Diagrams don't show it or any other source.

[sstocker31]

Been awhile since I've been able to get at this. I went to the junkyard and picked up a new cluster and a coil pack to try out. Installed the cluster first and the tach came to life.... One problem though, the brake and antiskid lights came on, so I took the cluster back out and compared part numbers....the old one is a 749AI and the new one is a 749AE.
I guess I'll have to go get an exchange.... and I have a spare coil pack too. Good thing JY parts are cheap

OH and RIP thanks for sticking with me on this one....I suck at electrical troubleshooting.

[sstocker31]

OK got the exchange part.....they didn't have the 749AI, so I thought I'd try a 749AB. Installed it and everything works fine now. Nice cheap fix....$25