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Tach Problem

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K

KeithViolet

Freshman Member
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1991 XJS when the car is cold the tach won`t move until I tap the dash. Is the repairable? Lubrication or something and is it easy to do ?
 
I don't know the answer, but the '69 E-type I am working on does the same thing. Only it fails hot or cold. But a tap on the instrument usually gets it going again.

It acts like a bad ground or something. I did check the wires on it, and all are secure.

I'm hoping to hear of a simple fix before I try to remove and replace the thing.

Bill.
 
My Spitfire does the same thing! I suspect its just dirty and needs cleaning.

Basil
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Basil:
I suspect its just dirty and needs cleaning.
Basil<hr></blockquote>

Carefully - like a clock.
D
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:


Carefully - like a clock.
D<hr></blockquote>

Actually, when I get ready to do my Jag Tach and Speedo, I am sending them to

Nisonger's for refurbishing. I wouldn't dare try to pull them apart myself.

Basil
 
I have the same problem with my 240's tach. A little tap is what I use to get it going. Sometimes it is more often than not...

Danny
 
Check the condition of the instrument cluster wiring connector where it plugs into the panel. the connector contacts or the female contacts in The panel connector contacts may have tarnish or corrosion that interfers with the signal. As the contacts heat up because of the tarnish, the resistance lowers and the signal would then be near normal. Clean the contacts with some steel wool.

Make sure that the battery is disconnected first so as not to fry anything.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>or the female contacts <hr></blockquote>
hmmmmmmmm
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>ay have tarnish or corrosion that interfers with the signal. As the contacts heat up because of the tarnish, the resistance lowers and the signal would then be near normal. Clean the contacts with some steel wool. <hr></blockquote>
....ok...I was already daydreaming...thanks for waking me up...
cheers.gif


Danny
 
FYI, I finally removed my tach and took it to a local instrument shop. They said it had a bad ground on the internal circuit board that they were able to fix.

It seems to work OK now, time will tell if this fix is permanent.

Question: does anyone know if electronic ignition setups (like Pertronix) will affect these electronic tachs?
 
Pertronic and Crane/Allison ignition ignition kits will not interfere with the tachs that this topic discusses. There can be problems with E Type tachs that have a positive signal drive but the tachs can be rewired. The XJ tachs have no problems with the Pertronic.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Healey 100:
But a tap on the instrument usually gets it going again.
snip
I'm hoping to hear of a simple fix before I try to remove and replace the thing.
Bill.<hr></blockquote>
I think that Jag had a special tool - "rubber tach tapping hammer" which might still be available.

smile.gif
 
Bob Stevenson, The tachometer arrangement I was refering to is a series 2 that uses the 12 volts to the coil primary circuit through the tach signal to get the drive. You are right in that the series 1 uses a sseparate transduder on the back of the cam drive. The positive drive on the series 2 is a little flakey with a Pektronic.
 
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