Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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If you have a multi meter, you should take a resistance reading of the one in the cup of hot water.
And the resistance of the one in your car on at ~ 0°C when it won't start.
Have you ever tried starting it with it disconnected? when cold
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27th Mar 2018 5:33 pm |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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Hi not sure how warm if it's cold tonight I'll try it by just keeping it in my pocket and see if it starts.
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27th Mar 2018 5:36 pm |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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Someone tried that already and it won't start.
If I get a meter and see what the difference is between hot and cold then get a variable resistor that makes it ajustable. The only thing is I need some plugs to make up a loom as I don't want to cut any wires.
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27th Mar 2018 5:55 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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shouldn't need a variable resistor.
Just switch another fixed resistor in.
But their is an easy way and difficult way, so need the values
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27th Mar 2018 7:49 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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Thanks. I'll take a look at that.
Be nice to know what your one is measuring on the car when it won't start (in case its faulty)
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28th Mar 2018 4:42 pm |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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I thought about that but found out the same sensor also feeds the temp gauge on the dash next to the fuel gauge mine won't start anything below 0 degrees I saw in another thread a picture of a resistor stuck in the car plug also the hotter the car is the less the resistance is but if you just unplug the sensor it won't start.
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28th Mar 2018 5:27 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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Firstly I would recommend you fit a new temp sensor.
Certainly for a Jag TDV6 owner has found a new sensor has resolved the problem and the old sensor wasn't reading that different to the new one, so the car/ecu must be very sensitive to an accurate/good reading.
However if you wish to you could purchase a 2.2K resistor
https://www.ebay.co.uk/itm/25-x-Metal-Film...nB1AgpUwGg
and fit a switch on the dash to connect this resistor in parallel with the coolant sensor.
This should mean that when the coolant sensor is reading around 0°C and ecu will be told its around 98°C
or if you were to use more difficult to find 2.4K resistor it would be told 95°C which is probably closer to your sensor dunked in boiling water.
This of course assumes the sensor is reading correctly!!! Would be really nice to confirm its value when the car won't start.
Check it actually works before drilling a hole in the dash and running wires in! I guess you could rig a switch up under the bonnet to test it
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28th Mar 2018 8:12 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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does the dash temp gauge read high when you have fitted the "boiled" temp sensor ?
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28th Mar 2018 8:21 pm |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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I think it only needs to be telling the ecu its about 50-80 degrees so any resistor from 3.8 ohms (80 degrees) to 11 ohms (50 degrees) should do it.
see link for how to test
http://www.disco3.co.uk/gallery/albums/use..._Resis.JPG
need to order some off amazon.
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29th Mar 2018 7:32 am |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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My method/calculation involved switching in a fixed resistor in parallel to the existing sensor.
The advantages of this are:
1) A simple switch can be used (rather than 3 terminal)
2) Only 2 wires need to run to the dash (not 3)
3) more reliable. Should the modification wires break the engine would still run happily
4) No break in signal when the switch is flicked (although still ensure what exactly will happen!)
5) less chance of noise being picked up rather than running the signal to the dash and back
6) no additional resistance/poor connections during normal operation
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29th Mar 2018 11:18 am |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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EDIT: Read your other thread. So you have faulty glowplugs. I was wondering if the over fuelling was getting round this
I guess what you would need to do is:
Turn ignition on and wait for glowplugs to heat and light to go out.
TUrn ignition off (or try and start car)
Flick switch so it reads HOT
turn ignition on and start (glowplugs would be off)
Flick switch and hope engine continues running.
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29th Mar 2018 11:25 am |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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I know the glow pugs are broken
So I would do the following:-
Pretend to use the glow plugs and try and start the engine-----fail
if this fails flick the switch to simulate above freezing or normal temp---start the engine
leave the engine running for a few mins ( as once started will restart easily)
switch off engine ----switch out fake temp signal
restart engine
I was looking an the maplin site and found this:-
https://i1.adis.ws/i/maplin/UH03D_1?w=365&...cale=en-gb
would this go from 0 to 10k ohms if so its 15p I think the wire and switch could be the expensive bit.
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29th Mar 2018 11:52 am |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10335
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so what are you doing to do with that 15p variable resistor ?
Are maplins still going ?
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29th Mar 2018 3:45 pm |
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Flapper
Member Since: 04 Feb 2015
Location: Gloucester
Posts: 327
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Tonight I went for a drive and when the temp was normal I measured the sensor on the 20k ohm range and it was 4.97 or 5 to make it easy..
So as it was on a 20k range is it a 5000 ohm resistor? This is for the temp gauge to be on normal if I want it to read cooler I'll put a 10000 ohm in.
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29th Mar 2018 5:14 pm |
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