Quote:
Originally Posted by 9fourteen
First off I get zero bounce on the tach. It doesn't move at all and I have checked that many times.
I did the ohm test described on Clark's garage first. I used my multimeter setup for resistance and I know how to use it becuase I tested the resistance on the ignition coil just fine. I had the multimeter connected to the same pins that I have the o-scope connected to in the picture above. I get 0 on both the speed and reference. Clark's also says to test the two outer pins and there should be a much higher resistance. That shows 0 too. I can't see how the bracket being out of alignment could cause the resistance test to fail. I would think that would be internal to the sensor. I could see the sensor reads being off if the gap was too great.
One thing when I first drove the car home I thought the speedometer was off. I don't remember where I read this but I think I read those sensors play a part in what the speedometer shows. Maybe the bracket is loose and it just worked itself too far out and it is no longer getting reads. I got some of the maintenance records on the car at it had a new clutch put in about 8 months ago. I am guessing that when that was done those sensors would have had to been out or at minimum disconnected. It is possible during that procedure they got messed up or not put back on properly.
The car only has 54k miles on it so there is a good chance they are the orgiinal sensors. Maybe the best solution would be to just pull them both and replace them and check clearence at the same time and adjust the bracket as needed.
I have read the nightmare of pulling the sensors and have them break off or just get stuck. Is it possible to just take the bolts out of the bracket and pull the whole assembly out and then remove the sensors for the bracket? Seems that would be a lot easier and you I could work on it on my bench and get proper angle on them when pulling. But, the sensors look long enough that they might go through the bracket and down into the bell. If that is the case the assembly might not pull off.
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I wasn't inferring that the sensor mount would affect the resistance. I was considering that if the mount had loosenend up and the sensors had moved beyond the .8mm gap, the sensors wouldn't have the impulse from the flywheel. I had a hard to remove sensor and I sprayed it with nut buster after removing the hold down bolt and left it over night. I then twisted the sensor back and forth a few times while pulling it up and it came out. You need to make sure there's a rag in the opening of the bellhousing so none of the small parts fall in. If you pull the mount and the gap is properly set to start with, then when you replace with new sensors, you'll have to reset the gap.
The speedo gets it's info from a spin sensor on the transaxle. The sensor is threaded onto the transaxle and there's a typical click-on connector on the end of it. It's possible you have a separate issue with that, either a loose connector or the sensor may be either defective or come unscrewed (not likely).
I had to replace a ref sensor recently and the I got the replacment from a supplier on ebay. It was an original Bosch unit, new, and was around $50. The ohmage value on the new ones was around 1k ohms.