I have been working around the engine compartment changing all the 90ยบ elbows into long radius sweeps (topic for another thread!). When I started it up again after having had the chassis battery switch off for a few days, the VDO dash tach no longer works. It does the initial self test with a full sweep of the needle, but indicates zero while the engine is running. Dash blower works, I haven't road tested yet so I don't know about the speedo. VMSpc gauges all seem to work as normal, including the tach. I think I may have jostled a connection at the back of the engine while standing on the trans, but I see noting loose. It won't keep me from traveling, but it is annoying!
Don
Some have a sensor that screws into the top of the bell housing with 2 wires going to it, but not sure on a 99.
More info: The engine hours showing on the tach looks correct.
Don
You can raise the bed and see if the sensor is screwed into the bell housing with the 2 wires. It is on the passenger side top of the bell housing. very easy to see if the wires are damaged which could happen when you were standing there.
That would make sense because that is the area I was working on the lift pump fittings. Though I was careful not to step on any of the wire bundles, they did get jostled when I was changing out fittings. Unfortunately, not so easy to see the top of the bell housing on that side because of the wire harnesses in that area. I can see a couple of two wire plugs, but the other sides of the connections appear to be wires coming out of the harness. Tys won't let me open the bed anymore today :o , so assuming everything else works as it should, it will have to wait until we get to our next destination. I will post a picture of the area with the plugs I mentioned circled... if you think either of these might be the culprit, let me know!
Don