Instrument cluster tach accuracy

[NPGuy]

I have a 1991 and am wondering if anyone has had any issues with their tach reading high? I don't have an external tach yet to compare it to but am thinking it is reading high.
I followed the procedure for resetting my idle after doing a bunch of work to the car and it still shows on the dash that it is idling just over 1,000 Rpms. It is nice and smooth and steady. I am planning on buying a photo tach to measure it with.

I had the dash apart to replace all the lamps and looked at the tach at that point. And cleaned up the connections and sprayed the needle shaft with some electronics cleaner lube.
Has anyone ever had to replace any of the components on the little PCB? I did find some videos on re soldering some of the components on the board for newer instrument clusters that had cold solder joints.
Any one?

 

[2stroke]

I haven't, but as a general rule, you can't trust a stock gauge. Usually the speedometer is close for safety reasons, but the oil, temp, tach etc. are not always accurate.

 

[NPGuy]

Seemed pretty tight when I took it apart and it just seems like it is idling way lower than 1,000 right now. The one post I read was fixing tacos that jump around by re wetting all the solder joints on the little board on the tach. Wonder if it would be worth taking it back out to check those and to measure all the resistors and caps just to be sure? I could not get the whole dash assembly out so I just pulled the front off and changed the bulbs that way.

 

[2stroke]

You couldn't pull the cluster out enough? That speedometer cable is a pain. Just pull harder, the cable will move.

 

[FR-425]

squeeze the clip and it will "slide" out. ...

 

[2stroke]

If you have giant meat paws like myself, the cluster has to come out a long ways to reach the speedometer cable.

 

[Maniak]

A trick to make it easier to get back there...

Gently pull the gauges out of the cluster while the cluster is still in there.. Now you can push the tabs in so you can push the wire harnesses backwards/out.. Once the wire harnesses are off the cluster it is easier to move around so you can squeeze/pull the speedo cable out.

For a cheap tach, I found a dwell meter at a yard sale (or swap meet).. I use that for checking low rpm speeds...

~Mark

 

[Jason94sport]

If it's running fine I wouldn't mess with it. It's a 91 why you need the Tach to be that accurate...

 

[mr cribb]

I haven't, but as a general rule, you can't trust a stock gauge. Usually the speedometer is close for safety reasons, but the oil, temp, tach etc. are not always accurate.

I couldn't agree more with this statement, this is precisely why I have aftermarket oil and water gauges.

The speedometer in my Semi and my 94 silverado are 3 mph off by GPS measurement.

The only tach issue I have seen on these rigs is the hanging 3k rpm issue which is solved by soldering the contact points again.

 

[NPGuy]

I just have a thing for liking things to work but I might just leave it be while I am ahead at this time. Got all the dash bulbs changed and dash already reassembled so time to quit.
Think I will just get a photo tach to compare it against. But I am still thinking it is reading high.
I use to own a dwell meter but have not seen one in 20 years, have not even seen a used one for sale in a long time. Guessing people don't know what they are even for anymore since all the new electronic systems have been out for so long now!
Thanks for the comments! Will update when I get a tach to compare it against.