Water temp gauge

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Walrus
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Water temp gauge

Post by Walrus » Thu Aug 24, 2017 6:32 pm

Hi from Orpington,

Owned 1998 1.8i for four years, bought with a tax refund from HMC when retired. Not sure if this is how a topic is posted but I do now really need help.
Water temp gauge not working, have replaced both sensors to be sure (no I am not Irish). Have also purchased and fitted used instrument cluster but same problem.
I have run an external wire from engine temp sensor and compared to wiring loom multiplug readings and they are very similar, have shorted out/earthed sensor wire and gauge works. on checking RAVE CD for the wiring layout etc it is made more difficult to work out as I have a twelve pin multiplug into the rear of the instrument cluster and the manuel shows a sixteen pin multiplug therefore the wires do not appear in the same format as I have.
I have used a multimeter on the reverse of the water gauge on the three connectors IGN, TU and GRD. I have a 12volt reading from IGN, Continuity on the GRD and as stated previously a reading on the TU.

Everything else works with no overheating, leaks or noises.

If anyone has any helpful suggestions I would appreciate them, especially with regards to the multiplug layout for my twelve pin colour codes to the relevant item.

Regards.

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Keith Williams
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Re: Water temp gauge

Post by Keith Williams » Fri Aug 25, 2017 7:38 am

Post moved to Technical Area where it will get more visibility rather than in the Welcome section.
1998 MGF VVC, 2001 Trophy 160 & 2013 MG6 GT TSE

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talkingcars
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Re: Water temp gauge

Post by talkingcars » Fri Aug 25, 2017 8:05 pm

Have you earthed the wire from the blue sensor, the gauge should go to max.
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Walrus
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Re: Water temp gauge

Post by Walrus » Fri Aug 25, 2017 8:32 pm

Hi, Thanks for responding. Yes earthed wire from sensor to engine and also to the bodywork and max reading on gauge shown both times. Have also created a temporary new earth from the GRD fixing screw on the rear of the temp gauge to the battery. I have also used electrical residue remover spray on the multi-blocks and the instrument cluster to no avail.

I feel I might have a fighting chance if I can work out the correct wires from the twelve wire multi-block and not the sixteen block as shown on every site displaying a wiring diagram I have managed to locate and then work backwards from there.

I've put it all back together and still no change. Fortunately it's not my main vehicle its just for the occasional fun day out with the hood down when the sun shines and the wife lets me out.

Anymore suggestions / advice would be much appreciated.

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Charless
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Re: Water temp gauge

Post by Charless » Fri Aug 25, 2017 10:04 pm

Trying to be helpful; your next step with the multimeter is to check continuity from sender connector to the back of the gauge or multiplug. It is not unheard of for sensor wires around the hot engine compartment which get thermally cycled to eventually go open circuit - or worse - intermittently so!
Have you come across this site? http://www.mgfcar.de/ Dieter has done all the hard work and gives you the resistance related to temperature for both the ECU and gauge temperature sensors.

Walrus
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Re: Water temp gauge

Post by Walrus » Fri Aug 25, 2017 10:27 pm

Thanks Charles,
Yes I have seen the site mentioned and it is very very helpful. I will try your suggestions although I am not that great with a multimeter and resistances, maybe this is a good time to learn?

I did think of running a wire from the temp sensor to the now spare instrument cluster TU terminal, placing it under the bonnet and then connecting a wire from the GRD to the battery earth and another from the IGN to the positive battery terminal and then letting the engine run. If it works / reads, i.e. the spare cluster gauge then I did think of then connecting the new TU wire to the rear of the fitted gauge thereby isolating any or all original wiring connections throughout the vehicle.

Thanks for your suggestions

frenchdave
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Re: Water temp gauge

Post by frenchdave » Wed Sep 13, 2017 8:42 am

I have a similar problem and have replaced the sensor,( Blue one), but nothing on the gauge. Can you tell me if you have fixed the issue and if so how? Thanks Dave

frenchdave
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Re: Water temp gauge

Post by frenchdave » Wed Sep 13, 2017 8:43 am

should have said mine is a 1999 mgf 120 bhp Cheers Dave

Walrus
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Re: Water temp gauge

Post by Walrus » Wed Sep 13, 2017 10:02 am

Hi Dave, No I am still trying. I attempted wiring the spare instrument cluster as described previously so that both clusters were wired independently and surprise the fitted temp unit worked. In my glee I dislodged the temporary earth lead to the battery from the spare cluster and the fitted unit stopped working which made me think it has to be an earth issue. I started again checking engine to body earth, sensor with a wire and clamp attached to earth, rear of temp unit direct to battery earth etc, etc, but no luck.
Although I replaced with new both temp sensors I am beginning to think it may be a duff new sensor. The original blue sensor unit is shorter in length than its replacement and I am wondering if I have been supplied with an incorrect unit but it does give an OHMS reading very near the Dieters figures so I am still at a loss. I will possibly try purchasing another new sensor but from a different source.
Still looking for wiring diagram to explain twelve block colour code connections.
Regards,
John.

frenchdave
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Re: Water temp gauge

Post by frenchdave » Wed Sep 13, 2017 10:26 am

John I have a book mgf electrics up to my 2000 will that cover yours if so will copy a photo of the circuits you need

ch-godalming
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Re: Water temp gauge

Post by ch-godalming » Thu Oct 05, 2017 5:25 pm

Watching with great interest. My '96 MGF VVC has not had oil temp gauge working for years and water temp (this one worked occasionally for a few months) for several years - recently replaced both sensors with ones that were stated to fit the exact year / model spec. Neither new sensor working; both gauges go to high if wiring shorted ie indicating gauge + wiring ok. Garage has obtained and tried several other sensors from motor factors - nothing working.

frenchdave
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Re: Water temp gauge

Post by frenchdave » Thu Oct 05, 2017 6:06 pm

Mine was fixed as i had brought the wrong sensor. Spoke to rimmers, and paid extra for a blue one, and it all started working. Maybe my ebay cheapy was too cheap

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