Tach reads low

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Oct 11, 2002 | 04:45 PM

flyloki

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Tach reads low

'94 F-250 Xcab 7.3 IDI Factory Turbo Diesel 5spd

My Tach is reading low (approx 1500 rpm) - doesn't move until you rev the engine and shows about 1500 at highway speeds. Any idea on where to check for faults? I can't seem to find this exact problem in the archives. Is there a crank sensor or is it coming off the coil? It still works so I'd rather not replace the whole cluster unless I have to. Has anyone done a write up on this?

Thanks,

JB

Oct 11, 2002 | 04:50 PM

flyloki

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Tach reads low

looks pretty straight forward. Is there some sort of ground I could check or clean on the the tach?

Thanks,

JB

Oct 11, 2002 | 05:10 PM

kioolt

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From: Bel Air USA

Tach reads low

The manual I have for a 93 diesel without E4OD shows the tach signal coming off of a engine speed sensor. The location of the connector for the sensor is at the top left hand front of the engine. It is a black connector with two terminals. One wire will be tan/yellow and the other wire will be dark green.

Oct 11, 2002 | 06:09 PM

flyloki

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Tach reads low

Thanks kioolt - gotta love those Beemers. I learned to ride on an R bike.

JB

Oct 11, 2002 | 06:47 PM

flyloki

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Tach reads low

Anyone know what sort of voltage values I should be getting off this sensor?

Thanks,

JB

Oct 12, 2002 | 05:27 AM

kioolt

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From: Bel Air USA

Tach reads low

The sensor should be 2000 to 3000 ohms is free air with no ferrous material in its immediate vicinity. Remove it before checking it. I've got a troubleshooting guide that I can scan for you if the sensor checks out good.