77 electric tach issue
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6th Gear
Joined: Mar 2011
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77 electric tach issue
While sitting at red light on way to cruise in, tach jumped to 4400 rpm and stayed there, when I got home I removed cluster and checked all connections and 3 inputs, found all to be good, sent tach to speedo shop and they said circuit board was good (which I thought was the problem from previous experience) but the armature inside the tach was bad, what caused this??? OEM filter has been removed for years and tach worked fine without it and does anyone know where I can get replacement or have mine repaired. Thanks for your help
Race Director
Joined: May 2006
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From: Dayton, Ohio
Thread Starter
6th Gear
Joined: Mar 2011
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Thanks Roger but don't understand how this would help, filter is only used to supress radio noise from tach operation in OEM radios and circuit board was confirmed good by shop I sent it to, armature inside tach head itself is shorted, since I've posted this earlier I tried known good circuit board with my tach and have same results.
Thread Starter
6th Gear
Joined: Mar 2011
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Yes, I need a tach head or to have mine repaired, the speedo shop I used said they do not repair them and referred me to Wilcox corvette, I've checked their website and head is not available, same results with Ecklers, ZIP and Volunteer. One of them offers a restoration service for $260 but does not say what that includes. Going to swap meet in Louisville KY tomorrow to see if I can find one.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Call Willcox or PM Ernie at this link , I'm sure he'll have the answers.
http://forums.corvetteforum.com/priv...newpm&u=225569
http://forums.corvetteforum.com/priv...newpm&u=225569
Le Mans Master
Joined: Sep 2002
Posts: 5,236
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From: Myrtle Beach SC
While sitting at red light on way to cruise in, tach jumped to 4400 rpm and stayed there, when I got home I removed cluster and checked all connections and 3 inputs, found all to be good, sent tach to speedo shop and they said circuit board was good (which I thought was the problem from previous experience) but the armature inside the tach was bad, what caused this??? OEM filter has been removed for years and tach worked fine without it and does anyone know where I can get replacement or have mine repaired. Thanks for your help
Also, with the work involved with removing the tach/board from a 1977 and given its 30+ years old, I would replace the tach board as well. I wouldn't want to rebuild and a year down the road, have to tear into the dash again with same problem.
So just a couple of additional considerations but do keep us posted. Here's link to article on tach board problems that may help with some background reading.
Tach Board Repair
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Thread Starter
6th Gear
Joined: Mar 2011
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Thanks cleanair for your reply, I will contact them tomorrow, no luck at swap meet today but did find new aluminum wheel lug nuts and ashtray door. I'm going to go ahead and replace board too, like you said, too much work to do again
Safety Car
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From: North Easton Mass
Rick B.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
UKMan-
Been out of town and just got this from Roger.
It is possible the analog movement is defective, but not likely.
Have you tried powering it up out of the car?
You can do this by running power, ground and a signal wire direct to the tach.
Also, you said you checked the connections but:
Did you do a continuity test on the wire from the tach to the distributor?
Do you have power on the power wire and did you verify the ground is working?
Best way to do this is to use a test lamp and use the existing wires. If the light comes on the test lamp, then you verified both are working.
You also said the tach jumped to 4400 and stopped! This sounds to me like a board issue and not a movement issue.
Run it up here and we can test the movement and/or the board for you while you wait.
willcox
Been out of town and just got this from Roger.
It is possible the analog movement is defective, but not likely.
Have you tried powering it up out of the car?
You can do this by running power, ground and a signal wire direct to the tach.
Also, you said you checked the connections but:
Did you do a continuity test on the wire from the tach to the distributor?
Do you have power on the power wire and did you verify the ground is working?
Best way to do this is to use a test lamp and use the existing wires. If the light comes on the test lamp, then you verified both are working.
You also said the tach jumped to 4400 and stopped! This sounds to me like a board issue and not a movement issue.
Run it up here and we can test the movement and/or the board for you while you wait.
willcox
Last edited by Willcox Corvette; Mar 28, 2011 at 03:17 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15