Intermittent Speedometer

Hi, I have a '98 Windstar with intermittent speedometer problems, amongst others, it seems that if I hit some bumps it stops working, then restarts on its own. The main problem is it screws with the transmission shifting. Any thoughts? Thanks for your input!

Hi,
Your problem would seem to me to be the vehicle speed sensor. Are you getting a check engine light? If the VSS info is interrupted for very long I think you should get the light. The sensor is hard to locate/change out. On my 96 with the 3.8, I can just see it from underneath/behind the engine. It is tucked up behind the exhaust ( the manual actually has you pull the exhaust manifold to change it) with a heat shield around it. You might try to examine the wire harness for damage or looseness. Other than that I don't know for a quick fix. Most likely the sensor is intermittently sending bad info.

Thanks for your help Busboy,
I had a chance to get under the van over the weekend. Apparently the trans was replaced with a factory rebuild and they never put back the heat shield! One of the wires (brownish/red) was melted and shorting out on the trans. I repaired the wire but it seems something is still wrong. It works ok for about 5-8 minutes then shuts down. I'm suspecting the sensor in the trans is shot. It must be some type of pickup coil? Maybe over heating because of the intense heat down there. What do you think? That manifold can't be but 2-3 inches above where the plug goes into the sensor.
Thanks for your advice.
Kenny

Boy, I suppose any of your suppostions could be correct. If you choose to change out the VSS, my manual shows no special procedures other than to properly support the exhaust manifold before you separate it to get at the sensor. That little bugger is really buried in there isn't it?

Hey Busboy,
I got under the windstar today. Pulled out the old VSS (didn't have to remove the manifold) and put it on the bench. I put it in my bench vise, hooked it up to a drill that has a throttle lock and hooked it up to my ac volt tester. It put out from 0 to 6 volts ac. depending on how fast I ran the drill. Now the real test. I got out my handy dandy propane torch, and warmed it up from a distance while I continued to spin it with the drill motor. Presto, after just a couple of minutes of 'warming' the voltage dropped to zero. Shut off the heat and in a few minutes the voltage comes back. Replaced it with one from Advance $28 bucks. Not too bad. I got it out by lowering the transaxle subframe by loosening the rear mounting bolts but not too far! I have smaller arms so I could worm my hand in there and pull it out without too much trouble. I also made up some heat shielding from aluminum sheeting I had laying around and some insulation. Thanks for your input.
Kenny

Hey Kenny,

good for you. I applaud your ingenuity in getting at the sensor and in developing a test to confirm your suspicions. I think these are the things that make home maintenance a kick. That is if you have the time.

Thanks for the update. I'll remember your methods if I have to change mine out at some point.

Mel