temp gauge.

Post by **callyspoy** » Sun Jul 20, 2008 5:49 pm

right, now my dad has yet to be able to make one work in his car. he has used two regulators, wired them up how he thinks they are supposed to be wired, used 5 different gauges(all pretty standard smiths ones) and 3 senders. now they all get "power", as in, they move to an on position when you turn the ignition, but none of them move any further than this. anyone got any ideas?

Post by **bmcecosse** » Sun Jul 20, 2008 10:13 pm

Well - if you short the sensor wire to earth - they should go full HOT.

Post by **Kevin** » Mon Jul 21, 2008 4:46 pm

Or pop the sensor into some hot water you will then see if it moves.

Post by **callyspoy** » Mon Jul 21, 2008 5:48 pm

it does indeed go full hot when you do that, and we did the glass of water test too! just amazingly baffled! makes me happy to have a capillary one!

Post by **Rob_Jennings** » Mon Jul 21, 2008 9:00 pm

is the sensor in the block? or the thermostat housing? (seen both)

if it appears to work fine but not in the engine then that suggests that its not in water, so you might have an airlock. assume when you remove the sensor you get water out of the hole? if not then replace it, then pump the hoses and run engine a little to get the air lock out of the system.

typical failure of boiling dry is...

temp gauge moves past normal, to hot then very hot then back to cold? ..... the back to cold is caused by the sensor now hanging in air rather than water because you have boiled dry!!! so an air lock in the system may give the same cold reading

Post by **callyspoy** » Mon Jul 21, 2008 9:26 pm

sorry, i may not have explained enough. what i mean is, we set up a new system and dangled the sensor in a cup of boiling water. nothing happened. dad had previously trested to see if it shorted out, which it did. so its all a bit odd. i personally think that it is probably a wiring fault, but HE is adament that its not. but we have tried so many different senders/gauges, they cant ALL be broken! anyone got a quick rundown of wiring for the gauge...

Post by **Matt** » Mon Jul 21, 2008 10:06 pm

Basically get a 12V supply (or preferably a 10V from the voltage regulator behind the speedo, but I dont think your dad's car has one?) and connect that to one side of the gauge, then connect the sender to the other!

If you dangle the sensor in boiling water it still needs an earth ;) wrap some wire around the thread and back to the earth on the battery and see what happens.

Post by **callyspoy** » Mon Jul 21, 2008 10:27 pm

yep, did that too with the earth. just plain old annoying! anyone ever had this problem before?

Post by **Mogwai** » Mon Jul 21, 2008 10:49 pm

If it goes to max when the sender wire is shorted to earth I would assume the guage is ok which would point to a faulty sender one other thing to check is that the threads & seat in the head for the sender are clean if corroded may not be allowing the sender to earth very well

Post by **Packedup** » Tue Jul 22, 2008 1:34 pm

Stick a sensor in a working engine. Check resistance with a multimeter with the engine cold. Warm the engine up, and keep checking the resistance - The warmer the engine gets, the less resistance there should be.

To check, set the meter to ohms and have one probe/ croc clip on the sender, the other on a known good earth (stat housing studs generally work, but the batter neg would be even better).

Post by **bmcecosse** » Tue Jul 22, 2008 4:19 pm

Or just throw it away - and get a capillary gauge - much better!

Post by **Packedup** » Tue Jul 22, 2008 4:30 pm

bmcecosse wrote:Or just throw it away - and get a capillary gauge - much better!

Apart from all that fragile tubing you have to route oh so carefully. I've got a capilliary in teh Midget, and it will be coming out in favour of an electric one as wires can only release magic smoke and be replaced whereas the ether filled tiny pipe can fracture and mean at least 50 quid for a new gauge

Post by **bmcecosse** » Tue Jul 22, 2008 8:34 pm

With care - they last a long long time - and they WORK!