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Author: Subject: speedo gauge question
jabbahutt

posted on 22/1/09 at 08:03 AM Reply With Quote
speedo gauge question

Morning all

Been tols my job is on the line so trying to keep myself busy with fun stuff.

Further to my earlier posts on my speedo sensor. Before ordering another i'd like to check how my gauge works i.e does the gauge send power to the snsor and count the number of times it earths or was the sensor generating a pulse when the meagnet went past and sending it to the gauge.

As the sensor is completely knackered I though that if I put a multmeter across the sensor wires and turned on the ignition if there is 12v the nthe gauges counts earths and if there is 0v then it was the sensor that generated a pulse and sent it to the gauge.

Is that right? the ford one generates a pulse and sends it to the gauge so I want to make sure before spending any money.

If the gauge is generating the power and sending it to the switch is there any way to use a ford electrroinc sensor as it has 3 wires a 12v, and earth and a wire that sends the pulse to the gauge.

Thanks for any help, I'm afraifd the electrical numpty has returned to haunt the forum

Nigel






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02GF74

posted on 22/1/09 at 08:33 AM Reply With Quote
quote:
Originally posted by jabbahutt
Been tols my job is on the line so trying to keep myself busy with fun stuff.
oh dear ..... Is there much work for captain chaos these days?

Before ordering another i'd like to check how my gauge works i.e does the gauge send power to the snsor and count the number of times it earths or was the sensor generating a pulse when the magnet went past and sending it to the gauge.

You said you had 2 wires? It could be either. Have you actually told us what make/model it is? What do the instructions show? Any diagrams in there or clues as to which it might be?

As the sensor is completely knackered I though that if I put a multmeter across the sensor wires and turned on the ignition if there is 12v then the gauge counts earths and if there is 0v then it was the sensor that generated a pulse and sent it to the gauge.
Possibly - most likely due to the small voltage generate by an inductive sensor, the input would be low. I suspect with a 'swtich to ground' (reed stich) you would see a voltage. I would suggest disconnecting the sensor from the guage abd measuring voltage across sensor input on the guage. Next test would be to get a 100 ohm resistor and radidly connect it between the sensor inputs i.e. simulating contacts closing - if the speedo needle moves, you have reed stich type input - ideally you want to short the inputs together without the resistor but I am playing it safe.

Is that right? the ford one generates a pulse and sends it to the gauge so I want to make sure before spending any money.
I am pretty sure that is the case; I do not know if it is 3 or 2 wire.

If the gauge is generating the power and sending it to the switch is there any way to use a ford electrroinc sensor as it has 3 wires a 12v, and earth and a wire that sends the pulse to the gauge.
yes - you would probably need a simple single transistor stage to effectively ground the sensors inputs together.









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jabbahutt

posted on 22/1/09 at 10:20 AM Reply With Quote
thanks for that.

The original sensor I believe was a smiths one with two wires, one to the gauge and one to earth.

apparently the new model of sensor is SS34 but i can't find anything on this on the net.

The Ford one is a 3 wire, one to earth, one 12v and one to the gauge. Wouldn't have a clue how to wire a transistor stage as suggested mayde a sketch required as and when I buy it.

No the only place there seems to be a job for Chaos is here keeping you guys on your toes with electrical expalinations

Thanks again
Nigel






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