What's up. I just got a used 88 744 Turbo but the tachometer is broken. My grandpa suggested that I check the sending unit. Any other ideas (I haven't checked the sending unit yet, so that could be it)? Also, I still have my crashed 91 744. Can I just pull the tach from that and put it in the new one.

Thanks.

PS
Can I take the 140 MPH speedometer from the 91 and exchange it for the 120 MPH speedo from the 88? What would I have to do

This problem seems to be common.., we have gauge problems in both our cars, but not tachometers, instead has the fuel tank meter given in in the 744, and a odd earth failure somewhere behint the gauge panel on the 760, which does that engine temperature and fuel gauge sometimes don´t work, but it will be fixed.

It seems as in almost all cases I have come across, the fuel gauge has been broken.

And especially VDO instruments have been sensitive for this, Those nippon (Yasaki)instruments seems to hold together better.

My tach went south in a 91 740. Needle fell all the way to the right when the ignition was off and read a constant 2600 when the engine was running. I pulled the cluster and it looks like the instrument panel of the Space Shuttle behind it. Nightmare of wire bundles etc etc. The tach is a complex mass of everything (diodes, resisters, transistors etc etc) under the sun. I just looked on ebay and found a used unit for $10. Problem solved.

bl

How does the tacho get impulses from the engine? Is it via the coil or something else?

My tacho does all manner of odd things whilst the car is running. I think that I will need to replace it (The instrument cluster's connections are fine), but I want to chack out every possibility before I condemn it.
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