Author Topic: 3 pin Temperature Sender  (Read 464 times)

Phaeton

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3 pin Temperature Sender
« on: August 15, 2021, 06:44:32 PM »
ST2W nephews engine, no gauges work, he has a Thornycroft panel but nothing is connected. On the outlet manifold on engine he has what looks like a 3 pin temperature sender, I suspected a live, a resistored feed to go back to the panel & a NO switch which closes on hot to put a light on the panel. However putting a meter across all 3 pins in any combination I get no readings at all.

So does anyone know if my assumptions are correct, have a wiring diagram for it & finally where are we likely to get a replacement?

mobile_bob

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Re: 3 pin Temperature Sender
« Reply #1 on: August 16, 2021, 01:00:20 AM »
it might be that one pin is 5vdc power supply
one of the other pins sends back a variable voltage based on temp
the remaining? ground maybe?


got any pictures of the sender?

bob g
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cobbadog

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Re: 3 pin Temperature Sender
« Reply #2 on: August 16, 2021, 07:00:54 AM »
For the cost of a new temp gauge I would replace what you have and use a standard car style one. My preference is always a mechanical gauge as they tend to be more reliable and no electrics other than a light in the gauge. Obviously electric ones can be installed as a complete unit and then the connecting of the wires.
Either way remove the fitting from the manifold and go to the spare parts shop and match the thread size and pitch. This will be the simplest and quickest way to have a gauge working.
Is there any wiring in the dash board? If not best to start from scratch from my experience with electrickery. I could have spent hours tracing old wires on the Vintage David brown 30C tractor but instead bought the colours required and made my own harness in far less time. Plus I now know all the wires are in good condition with no fractures or corrosion.
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Phaeton

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Re: 3 pin Temperature Sender
« Reply #3 on: August 16, 2021, 08:19:30 AM »
I have only a very poor image of the sender, I was leaned over a running engine I should have checked it & realised how poor it was.



This is the panel that is in the boat, but we're not sure if it has ever worked with this engine as the anecdotal history says the engine was replaced with a recondition one around 5 years ago, but we don't know if it was of the same type or not.



But nothing works on the panel apart from the stater button & the ignition warning light which is just floating in the back of the panel.

I think as suggested the obvious answer is to remove the existing sender & gauge, by a matched set & get a convertor to go from the large current thread to a more usual one, somebody has suggested it might be 5/8th UNF is that likely?

cobbadog

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Re: 3 pin Temperature Sender
« Reply #4 on: August 16, 2021, 12:32:33 PM »
Yes it is likely but I don't think BSF will be the thread for a plumbing fitting. I am not familiar  with your type of sender so it would be best to remove it and the oil pressure sender and match a pair of gauges up and install the new ones.
Does the tacho work and is it electric or cable driven?

Is best' to measure it to be certain. The pic unfortunately is not a lot of help.
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Phaeton

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Re: 3 pin Temperature Sender
« Reply #5 on: August 16, 2021, 07:02:19 PM »
Tacho as seen in the image is electric, which I'm led to believe works from the alternator, however whether the alternator supports driving a tacho, I don't know. I'll have to get back onboard to make further investigation, only issue now is I'm getting further away from the boat as it cruises South.

cobbadog

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Re: 3 pin Temperature Sender
« Reply #6 on: August 17, 2021, 07:26:49 AM »
That is a tricky one, running off the alternator. Voltage output won't run a tacho, or I don't think it can unless a cable runs to the back of the alternator. The "UP" side of the boat cruising further away from you is that you get off the hook!  ::)

Anyway I'm sure you can work something out and you know my thoughts about replacing the gauges with new ones and best choice are mechanical gauges and not electrics in my books. Having said that I'm still very interested in the outcome of the project and hope it all works out well.
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Phaeton

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Re: 3 pin Temperature Sender
« Reply #7 on: August 31, 2021, 07:43:32 AM »
Just to close out this part of the story for those who are interested I hate threads that don't have a resolution. On Sunday I travelled down to near Milton Keynes & fitted an electrical sender & gauge, I would have gone with a capillary but wasn't sure of the route, but once installed & he set off again it sits nicely just over 80 degrees. Not sue how accurate it is but that's not the important thing, if 80 is the normal he now has a visual on the not normal.

Thanks for everybody's input.

cobbadog

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Re: 3 pin Temperature Sender
« Reply #8 on: August 31, 2021, 12:21:12 PM »
Thanks for the update on this project. It sounds like a good outcome and whenyou mention 80' do you mean 'F or 'C ?
Hopefully 80'C as that sounds to me about right.
In time we hope to hear that all the other niggling problems have been resolved and that the engine is running nice and smooth.
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Phaeton

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Re: 3 pin Temperature Sender
« Reply #9 on: August 31, 2021, 12:59:23 PM »
Sorry Celsius

cobbadog

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Re: 3 pin Temperature Sender
« Reply #10 on: September 01, 2021, 05:42:47 AM »
I would be happy with that temp. Lets hope that your Son gets a lot of enjoyment out of being on the water in a narrow boat. I spent a very short time on one many years ago in the mid 1980's, very enjoyable and relaxing.
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mikenash

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Re: 3 pin Temperature Sender
« Reply #11 on: September 01, 2021, 08:06:22 PM »
That is a tricky one, running off the alternator. Voltage output won't run a tacho, or I don't think it can unless a cable runs to the back of the alternator. The "UP" side of the boat cruising further away from you is that you get off the hook!  ::)

Anyway I'm sure you can work something out and you know my thoughts about replacing the gauges with new ones and best choice are mechanical gauges and not electrics in my books. Having said that I'm still very interested in the outcome of the project and hope it all works out well.

We have diesel engine RPM controllers here at my work that take a signal off the alternator - they simply sample the Hz and use the increase/decrease in that as an indicator of engine RPM.  Cheers

cobbadog

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Re: 3 pin Temperature Sender
« Reply #12 on: September 02, 2021, 06:50:09 AM »
Hi Mike,
Boy haven't I been left in the dark with improvements. I have not heard of these type of senders but I do live almost at the back of a cave here in Oz.
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Phaeton

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Re: 3 pin Temperature Sender
« Reply #13 on: September 02, 2021, 09:49:41 AM »
Found this Utube https://www.youtube.com/watch?v=yguFw2V1F2M on Alternators

cobbadog

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Re: 3 pin Temperature Sender
« Reply #14 on: September 02, 2021, 12:20:46 PM »
Chheers for the link. I think I just got a bit closer to the cave entrance.
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