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Tachometer Question

M

markk

New member
I have a 1989 XR4 the tach climbs in RPM when cranking when the motor starts the tach goes back to zero, I checked the grey wire which I believe is for the tach and have continuity...What am I missing?
 
12v and ground to the tach. The voltage on the grey wire should be min 3.5 VAC to gnd at idle, 5-7 at approx 2000 per my manual for the 90 of mine but should be the same for yours.

If the tach is good then your rectifier output may be bad. The tach responds to (counts) the charging sine waves applied to the rectifier/regulator module by the two yellow wires attached to it from the charging coils under the flywheel. As the engine speed varies, the number of pulses per unit time varies. Your symptoms are confusing to me however is determining just which is at fault.

HTH,
Mark
 
You have nothing to lose by squirting a few drops of WD-40 into the tiny switches on the back and work them back and forth several times...note the original setting 1st. Corrosion builds up in the switches and sometimes the WD-40 improves electrical contact.
 
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