Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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As above, have a small idea what im doing (checking 12v power) but need a quick lesson on how to use it.
I need to check oil and coolant temp sensors (for the dials) to make sure they aren't broken, can this be done with a multi meter, and how would i go about doing it?? Will the sensors need removed or can it be done with them in place?? What setting will the meter need to be on etc??
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Generation
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Registered: 7th Jul 09
Location: Essex
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Surely you have mechanical knowledge?
If you can change a tyre you know everything
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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And i can't change a tyre.
Electrics have never been my strong point.
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Generation
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Registered: 7th Jul 09
Location: Essex
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Can you change a wheel or wiper blades?
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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I can do most things mechanical, but when it comes to electrics, the mind goes blank lol.
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3CorsaMeal
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Registered: 11th Apr 02
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I bought a good issue of practical mechanics magazine that had a few pages feature on using a multi meter.
Those magazines are worth the money, they aren't just pretty SLR photos of cars with silly expensive wheels and broken suspension.
Am sure there must be a good guide online somewhere, its just checking resistance etc.
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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Yeah have picked up on some stuff via online/youtube guides etc.
Battery is charging fine lol.
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Dom
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Registered: 13th Sep 03
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If they're temperature sensors then they're likely resistive based (usually, higher the temp lower the resistance/Ohms) and tend to be simple two-pin sensors - remove sensor plug, multimeter lead on each pin, select resistance on your multimeter (denoted by the Ohms symbol) and start off around 100K/200K Ohms and decrease with the increase in temperature (they tend to have huge ranges, ie - 100k to 10 Ohms etc).
It's worth doing a Google for the datasheet and seeing if you can find one for the part as they tend to state the working temperature vs resistance range which will give you a better idea if it's working correctly.
quote:
Originally posted by Generation
Surely you have mechanical knowledge?
If you can change a tyre you know everything
And you moan about others acting like cunts 
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
User status: Offline
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The 3 sensors im testing only have a single wire going to them. Mainly just for the dash gauges.
Should the single wire have 12v going through it, or does it not work like that??
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Dom
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Registered: 13th Sep 03
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Measure it at the sensor rather than at the dash 
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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Yeah that's what i was doing.
Should i be able to put the positive in the wire, earth out the black, and get 12v on the multi meter with the ignition on??
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
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The sensor shouldn't need power, if its a single wire then its probably resistance to ground. In which case set the meter to resistance (ohm symbol), polarity isn't even important but red probe to the plug where the car wiring would go, and black probe to the case of the sensor, thread where it screws in to the block, or anywhere else that looks like earth when its installed.
The exact range in resistance you'll need to try a few stops on the dial and see where you get the reading - as Dom says you'll typically need some knowledge of the sensor to tell what is a normal reading.
[Edited on 02-07-2014 by Ian]
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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How would i go about checking those single wires to see if its got a good earth??
Problem im having is the oil temp gauge dosn't work, and the coolant temp gauge dosn't climb as high as it should, barely moves off the bottom line but does move. Ive tried grounding out the wire to see if the sensors are broken, but no movement on the gauge. The "stop" light is on, very dim, which would also suggest a bad earth somewhere.
The sensors are linked to the "stop" light which would suggest a bad earth.
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Generation
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Registered: 7th Jul 09
Location: Essex
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I done it because he done it to me. Showing him how annoying and unnecessary it is.
Anyway, let's move on
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
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You can probably assume that the sensors do if they're working OK, ie the ECU is happy.
Need the spec of both the sensors and the gauges before being able to diagnose why they're not moving. Are the gauges not configurable?
Dim stop light does indicate an earth problem, ground loop would give you that sort of symptom. How are they earthed currently?
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Corsa_Sport21
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Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
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So, turns out a burnt out track in the ribbon on the back of the clocks was to blame for all the issues. New set of clocks and all is good now.
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taylorboosh
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Registered: 3rd Apr 07
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Hope they have less miles on
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Corsa_Sport21
Member
Registered: 13th Apr 08
Location: Leven, Fife. Drives : 205 GTi
User status: Offline
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They did, had 85k on them iirc. Switched the speedo unit over though to retain the genuine 190k miles lol. Its an honest car, and clocking it really wouldn't have worked in my favour.
Reckon it would have been a hard task finding another set with that amount of miles on them. Bet there isn't much that's made it to that mileage.
Old clocks looked like this....
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