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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Fri May 15, 2015 17:44 Post subject: Testing a new temp gauge sender |
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Right, I have a new sender for my temperature gauge and before I install it I would like to know it is going to be better for my gauge than the one in the car already. Thing is the one in the car already seems to work but registers only a tiny amount of movement when the car is hot. Could be the car runs cold which is why I wanna checkout the new one first.
Can anyone suggest how to test it.
http://www.ebay.co.uk/itm/291330030530?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT |
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Posted: Fri May 15, 2015 17:44 Post subject: Google Ads keep the POCUK free to join! |
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peteinchad LifeTime Member
Joined: 07 Jan 2013 Posts: 15079 Location: UK
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Posted: Fri May 15, 2015 18:26 Post subject: |
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I had exactly the same thing with my truck.
I spent over three years thinking that my engine was running cool as the gauge never got to the 1/4 mark.
Fitted a new sender and it gets up to the middle of the gauge.
They are easy to fit so put it in and see if the gauge shows a more normal reading. |
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Simon_W *******
Joined: 21 May 2013 Posts: 4881 Location: Watford
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Posted: Fri May 15, 2015 19:30 Post subject: |
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Have you got access to a thermometer of the appropriate scale? Digital multimeter?
If so you could put the end of new sender in a jug of hot water (don't get the electrical end wet, just in case) and measure the resistance as it cools and the temperature drops. Then either do the same with the old sender, or leave it in situ and measure the rising coolant temperature and resistance with the rad cap off and the engine running.
Or just do as Pete suggests. Put it in and see what happens. |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Fri May 15, 2015 19:30 Post subject: |
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peteinchad wrote: |
I had exactly the same thing with my truck. |
Must be twins these two, senior and Junior!! |
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peteinchad LifeTime Member
Joined: 07 Jan 2013 Posts: 15079 Location: UK
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Posted: Fri May 15, 2015 19:35 Post subject: |
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helijohn wrote: |
peteinchad wrote: |
I had exactly the same thing with my truck. |
Must be twins these two, senior and Junior!! |
It is probably easier to change it than to test it tbh. |
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Simon_W *******
Joined: 21 May 2013 Posts: 4881 Location: Watford
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Posted: Fri May 15, 2015 19:40 Post subject: |
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peteinchad wrote: |
It is probably easier to change it than to test it tbh. |
Agreed, except that a some coolant will have to be drained (or lost) to swap them over. |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Fri May 15, 2015 19:55 Post subject: |
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Simon_W wrote: |
peteinchad wrote: |
It is probably easier to change it than to test it tbh. |
Agreed, except that a some coolant will have to be drained (or lost) to swap them over. |
Yes, I think a swap is the way to go and after all, I bought it so I should use it.
Pity I can't rest the new one on the rad header and see if it does owt when the car gets hot.
Another point is I didn't want to mess if it wasn't going to cure the low reading but saying that I am 95% the sender is naff. I don't fix things if they ain't broke.
I'll have to work damn fast to swap 'em quickly so as to not lose fluid; should I use a sealant on the new one's thread? |
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Simon_W *******
Joined: 21 May 2013 Posts: 4881 Location: Watford
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Posted: Fri May 15, 2015 21:06 Post subject: |
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I used PTFE tape when I replaced mine. I couldn't see that it would do any harm. Better than risking over-tightening the fitting trying to stop a leak.
Is there a drain tap at the base of your radiator? If so, it makes it very easy to draw off a litre or so into a container and drop the level below that of the sender. Then replace, of course! |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Sat May 16, 2015 8:34 Post subject: |
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Simon_W wrote: |
I used PTFE tape when I replaced mine. |
I started using a threadlock a few years ago instead of PTFE tape on CO2 unions and compressed airline unions - I was thinking of trying that but I will probably end up using PTFE tap cos threadlocks don't like wetness..
I might syphon some coolant from the rad - I haven't noticed a drain tap and it would probably taking off the bash plate to access it. I am feeling dead lazy today and it should really be a five minute job. |
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peteinchad LifeTime Member
Joined: 07 Jan 2013 Posts: 15079 Location: UK
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Posted: Sat May 16, 2015 9:00 Post subject: |
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The one I got had some threadlock already applied to the threads - I still used PTFE tape though. |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Sat May 16, 2015 9:03 Post subject: |
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peteinchad wrote: |
The one I got had some threadlock already applied to the threads - I still used PTFE tape though. |
Oh dear, make up my mind time. Sunny today so I am on it. |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Sat May 16, 2015 12:38 Post subject: |
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Well I fitted it and now instead of rising to cold the gauge sits at off until the engine heats up then it goes to where the other sender sat which is just above off. |
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peteinchad LifeTime Member
Joined: 07 Jan 2013 Posts: 15079 Location: UK
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Posted: Sat May 16, 2015 12:49 Post subject: |
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Try earthing the wire that goes onto the sender - the gauge should go up to hot.
If it doesn't then it is either the gauge ot the wiring. |
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helijohn LifeTime Member
Joined: 24 Nov 2003 Posts: 2612 Location: Seaside resort
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Posted: Sun May 17, 2015 11:43 Post subject: |
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peteinchad wrote: |
Try earthing the wire that goes onto the sender - the gauge should go up to hot.. |
Reminds me of my early days of DIY. I tried it; I expected the gauge to rise slowly but it fllcked up to hot so the wiring is intact then. |
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peteinchad LifeTime Member
Joined: 07 Jan 2013 Posts: 15079 Location: UK
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Posted: Sun May 17, 2015 11:59 Post subject: |
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... and the gauge is working.
I wonder whether the PTFE tape is insulating the sender from the block so you are not getting a circuit.
I assume that your sender has only one electrical terminal on the top of it.
If it has only one terminal then the circuit is completed by the threads being in contact with the metal of cylinder head.
Try wrapping a bit of bare wire around the body of the sender and connecting the other end to earth. |
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