Intermittent Tachometer

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Nov 15, 2013 | 09:27 PM

uh60

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Intermittent Tachometer

I have an 88' F250 7.3 ZF5 speed. My Tachometer is intermittent at best, some times it doesn't work, or it's not reading accurately to where it will be indicating 1200 rpm's and I know that it is well over 2000 by the sound. And once in awhile it appears to be reading correct.

I figure that is has to be a loose wire or it's shorting out. But I can't find anything on the wiring for the Tach in any of my Manuel's. Where does the Tach get it's readings from and what color are the wires so I can trace them and see what the problem is.

Nov 15, 2013 | 10:41 PM

SEH43

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From: Salem, OR

I have an 86, 6.9, but they should be the same. It is located on the ip gear cover, facing the front of the engine it is sticking out at about 1 o'clock. It has 2 wires comming out of it. I would also remove it and clean the face of it well.
Hope this helps.

Nov 15, 2013 | 10:57 PM

uh60

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Awesome thanks.

Nov 15, 2013 | 11:41 PM

Dark Horse

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These 2 threads have some information about possible sensor replacements you might find useful. The symptoms you describe are usually the sensor and the most common fix is a new sensor from ford they are 80+ occasionally you can find one on eBay or amazon for less but they are when and where you find them. The Ford part is #E5TZ-17B384-A hope this helps.

https://www.ford-trucks.com/forums/1...er-sender.html

https://www.ford-trucks.com/forums/1...ital-tach.html

This photo shows the tach sensor on the lower left

Mark

Last edited by Dark Horse; Nov 15, 2013 at 11:47 PM. Reason: added photo

Nov 16, 2013 | 01:37 AM

uh60

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I hope it's just the wiring. But I will find out tomorrow. Thanks.

Nov 16, 2013 | 09:38 PM

uh60

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It's not the wiring. Everything looked good. I pulled and cleaned the sensor and put it back. Now it either doesn't work at all or it's right on. So it must be the sensor. But it is working more often now so that's a plus.

Nov 16, 2013 | 11:42 PM

Macrobb

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I'm pretty sure that it's water(moisture) getting inside it and partially shorting it out. Check for cracked insulation right where the wires go into the unit.

These things seem to fail on our trucks; they just seem to have less of a lifespan than the rest of the engine. You're going to have to replace it, one of these days.

BTW, do check out the links Dark Horse posted -- a DIY sensor like that works just as well as the original, and it's been a good 14 months for me without issue, so I'm happy(and it only costing $8+time isn't bad either

)