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catwithboost
09-05-2004, 11:58 PM
What sensor runs the Tach? Changed cam sensor and DIS still no tach. When you turn the engine over the speedo jumps. :confused: Is it the Crank sensor?

J.D.
09-06-2004, 12:07 AM
Pin 12 on the DIS (tan/yellow wire).
The vehicle speed sensor runs the speedometer.

MercXr7-5speed
09-06-2004, 09:25 AM
Funny you mentioned the speedo jumping. I just started putting my 89 xr7 back together and when I started it it did the same thing. It did it before I parked it but not often enough to be a concern to me. I has done it about 4 or 5 times since I put the motor back together. The milage goes up too. After it sarts all is ok though. If you find any solution to this problem please keep me updated. Thanks.

Joe

bigg_boyys_SC
09-08-2004, 09:20 PM
Check your email.

Mike Puckett
09-08-2004, 09:30 PM
I've had an intermittent tach on my 35th for several months. It comes and goes randomly and doesn't affect the car at all. The VMM is getting a tach signal and I've got good 12v, ground, and a tach signal on the backplane connections for the tach itself. I was planning to swap out the tach to see if tach was bad and I brought a scope home from work to look at the tach signal itself.

J.D.
09-08-2004, 09:49 PM
Do you know which trimmer on the tachometer is used to calibrate it - the one with the red screw or the one with the white screw?

Mike Puckett
09-08-2004, 11:45 PM
I suspect that they use a dual point calibration and both are used. One is for the low end and the other is for the high end. But which is which? I don't know. I researched the chip. It's an LM1819 or an ECG1670. Both are out of production.