Donald J . Sparks

did the same thing on my 84 the tach would go nuts or not work at all changed the filter and everything is fine . D . J . Sparks 02-01-08

jtg7582

[img]dsc00176[/img]

Papa835

Who carries the Tach Filter? Is it a GM part only??

Pop Evans

On my 90 that tach was reading about 4-5 grand at 60 mph. There is a resistor pac on the printed circuit board on the cluster that goes bad over time. If you can solder and have a digital meter it's a simple fix to add a resistor to the board to fix the problem. 99% of the time the filter will not help a high reading tach. I would be glad to provide more details if anybody want's to tackle it. The biggest PITA is getting the cluster out and in and out and in
Regards Pop

rodj

Year model helps when asking a question
Filter is discontinued from GM

http://www.rodneydickman.com/CorvetteTachFilter.html

ddahlgren

My 91 tach reads about 10% too high but is steady and the oil temperature gauge reads very low with a new sender and wires look just fine, all the other gauges work fine and assume they use the same ground in the cluster. At cruise around 70 I get 2400 rpm and idle reads around 870-900 WOT upshifts are at 5800-5900 which seem too high. I have checked the cruise rpm and with a scan tool the rpm reads 2000 and oiltemp reads around 200 degrees with a coolant temp of 190 which all makes sense to me. Also the intermittent and park on the wipers works about 50% of the time. Looking at the FSM the only common thing I can find is the connector on drivers side firewall behind the battery. The FSM says to check it for water before diagnosing a tach error problem. Has anyone ever found a problem with water getting into this connector?

scottvettec4

Would you be kind enough to send the information on repairing the resister. Thanks so much.

vetteoz

http://forums.corvetteforum.com/c4-g...ch-repair.html

corvetteronw

I have a spare tach filter that I bought from Vette2Vette. I never installed it though and planned to modify the board instead.
If someone wants it I will ship it for $20 total. 91 A4.