Tachometer Problem

[bwb3]

My '92 with 76K miles idles, accelerates and shifts normally. However, the tachometer now shows about 300 RPM idle, shifts with normal acceleration at 2,000 RPM, 3,000 RPM with brisk acceleration. Car cruises at 70 MPH at 1,500 RPM. It works smoothly so I don't think it is sticking, possibly just not getting or processing the electrical signal.

Is the problem pinpointed to the tachometer guage, and not a sending unit, if the engine is operating normally?

Can the tachometer be removed from the guage cluster and replaced (swapped with a used unit)?

I had similar problems with my Volvo tach but it affected the transmission shifting. My mechanic sent the tach off to be rebuilt. A place in VA, I believe.

Thanks for any insight.
Gene

[Hocrest]

Not sure what the problem would be??

I have a gauge cluster I can send you, the mileage is much higher than yours so you would probably want to try to swap the tach out rather than use the whole cluster.

[Trevor]

Originally Posted by bwb3

My '92 with 76K miles idles, accelerates and shifts normally. However, the tachometer now shows about 300 RPM idle, shifts with normal acceleration at 2,000 RPM, 3,000 RPM with brisk acceleration. Car cruises at 70 MPH at 1,500 RPM. It works smoothly so I don't think it is sticking, possibly just not getting or processing the electrical signal.

Is the problem pinpointed to the tachometer guage, and not a sending unit, if the engine is operating normally?

Can the tachometer be removed from the guage cluster and replaced (swapped with a used unit)?

I had similar problems with my Volvo tach but it affected the transmission shifting. My mechanic sent the tach off to be rebuilt. A place in VA, I
believe.

Thanks for any insight.
Gene

Although the sender unit transmits a digital signal it could be missing impulses even though this is unlikely. You must be sure of what is wrong before spending time and money.

Have the actual engine speed checked with and independent test instrument. Any good service set up should have one. You may even be able to find a friend who has one. I have one in my home set up.

A shop should also be able to test the sender unit with a scope, with little charge out time involved.

[bwb3]

Thanks for the offer Dave. Will do a little more sleuthing first per Trevor's recommendations. I say the car is running and shifting normally because the reving and idling sounds the same as when the tach was working normally. Come to think of it, it started acting up after the tranny rebuild (?).
Gene