Tach reading high
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Instructor
Joined: Jan 2000
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From: Fullerton CA
Tach reading high
Noticed that the tach in my '80 was reading about 500 RPM higher than normal while cruising down the highway tonight. Wasn't sure if the tach was high; the speedometer was low; or what. After exciting the freeway, the engine was idling normally, but the tach was reading about 500 RPM high still (~1150 RPM). Any tips on why my tach would be reading high, and how to fix it??
Thread Starter
Instructor
Joined: Jan 2000
Posts: 163
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From: Fullerton CA
Re: Tach reading high (av8vito)
Hmmm . . . no comments huh? Before I pull the tach to see about replacing the circuit board, I was hoping someone else had already experienced this problem, and could give me any alternatives befroe I dive into the tach gauge cluster. Been in there before, and it's a PITA. Guess I'll end up pulling the tach/speedo again. Good opportunity to fix the wiper switch, and upgrade the speedo to 145 MPH. Maybe this isn't such a problem!!
Le Mans Master
Joined: May 1999
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From: Texas
Re: Tach reading high (av8vito)
Question: When you turn the ignition on without starting the engine, is the needle on 0 rpm's? If not, you may simply need to pull needle off (Carefully!) and push back on resetting it at 0. If this is not the case, have no idea.
BTW, I have an old circuit board for an 82 that may also apply to an 80. If you research and it does, its for sale. I bought a replacement board thinking a tach problem I had was the board. It wasn't, so I have a perfectly good tach board for sale.
BTW, I have an old circuit board for an 82 that may also apply to an 80. If you research and it does, its for sale. I bought a replacement board thinking a tach problem I had was the board. It wasn't, so I have a perfectly good tach board for sale.
Thread Starter
Instructor
Joined: Jan 2000
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From: Fullerton CA
Re: Tach reading high (Larry82)
Yeah, my needle is on zero at start. In fact, the tach reads fine for the first hour or so of operation. After running for awhile, it starts creeping up despite a steady speed. Looks like I'll be changing the circuit board.
Thanks for the offer on the circuit board. I'll e-mail you when I get into the dash.
Thanks for the offer on the circuit board. I'll e-mail you when I get into the dash.
Instructor
Joined: Sep 2000
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From: Brooks GA
Re: Tach reading high (av8vito)
I've got the same problem with my 79 except it seems close at idle but is off around 2 grand at 60. First time I drove it and saw over 5 grand at 60 I freaked. Let me know if you find a fix.
Kip
Kip
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
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St. Jude Donor '06-'10, '13
Re: Tach reading high (Shark79)
My 1980 has been tested on two dynos. Both showed the tach 100 - 150 RPM high under 1000 RPM.
Then anything about 1250 RPM, the tach would read 500 RPM high.
I have just lived with this and learned to subtract when I look at it. I would like to know if a new circuit board would fix this.
If so, I may have that excuse to open up the dash ( :U ) and fix the clock ( :rolleyes: ) at the same time.
[Modified by BSeery, 11:24 PM 2/24/2002]
Then anything about 1250 RPM, the tach would read 500 RPM high.
I have just lived with this and learned to subtract when I look at it. I would like to know if a new circuit board would fix this.
If so, I may have that excuse to open up the dash ( :U ) and fix the clock ( :rolleyes: ) at the same time.
[Modified by BSeery, 11:24 PM 2/24/2002]
