Kit Car electronic Speedo Problem

[blooka]

Hi sorry to bother yall but got a problem with my speedo finally been able to get out in my tiger cat e1 and all was well, speedo worked fine then it dropped down to 10 miles an hour when i was going about 50. its a digital one with a 2 wire magnet speed sensor fitted to the prop. Im hoping its not the clock thats had it as they look real expensive checked wiring to speed sensor and when the magnet is on sensor i get continuity at the speedo plug, was told i should get a/c voltage when wheels spin up is that correct? i did try that with multimeter and got no voltage, not sure if this is right. Hope someone canpoint me in the right direction cheers dave this was on axle stands in fourth gear

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[plugsandsparks]

I would start by cleaning the prop flange including the extra lump that is used for pick-up. I would then check the gap is correct between the lump and sensor. If it still fails i would replace the sensor. Yes you should see an a/c signal but it can be tiny so you need a multimeter that measures mV or use a scope. The prop would need to be spinning to get a decent signal so be careful, lol

 

[blooka]

I would start by cleaning the prop flange including the extra lump that is used for pick-up. I would then check the gap is correct between the lump and sensor. If it still fails i would replace the sensor. Yes you should see an a/c signal but it can be tiny so you need a multimeter that measures mV or use a scope. The prop would need to be spinning to get a decent signal so be careful, lol

thanks for the info
i will check gap and clean, if thats no good i will buy a new sensor,any idea where the best place is to buy a new 2 wire sensor
cheers
Dave

 

[plugsandsparks]

I get all my sensors from RS components.

This one is an example

RS PRO Magnetic Pickup | RS

uk.rs-online.com

BUT, you really need to work out what type of sensor works with the clocks as there are many different types, you may be lucky and the sensor part no may still be on the old sensor.

 

[static zap]

Some sensors have a biasing magnet to see metal teeth -- It appears to be seeing the irregular surface .
(first thought try a slightly larger gap )....
As others have said -failing that a different sensor !

 

[blooka]

Thanks for all the info guys
thought my car just had 1 magnet turns out it should have 2
i didnt build the car so wasnt sure.
had a look on prop and seen where the other should have gone fitted another magnet and it worked
typical me going round the houses as usual.
thanks again for the info all
dave