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Temp Gauge and Sender issues


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Hello all,

 

I've recently installed a fairly new Lister LPW3 replacing an old one of the same model that was beyond repair.

I've come to link up the Temp gauge and found that I have two spades on the temp sender, to be honest I can't recall whether my last one had two or not, but I've tried every combination I can conceive to try and get the Temp gauge to show something but no, nothing.

 

Now, my temp gauge was on the boat when I bought it and a quick Google has lead me to find an identical looking one here on Amazon, which leads me to believe it's a cheap pile of sh*te. But that gives you an idea for the wiring, one pos, one neg and one single sender cable. Also worth noting it seemed to work fine on my previous engine.

 

I've tried the sender cable on both spades of the sending unit and tried putting and earth cable on the opposing spade simultaneously, then tried a live lead from the ign. accessories and still nothing. 

 

I checked the sender unit by putting a multimeter on the spades set to ohms and found it does appear to be working (although I didn't test it methodically, I just noted it was reading something after being run for 15-20mins and the number slowly decreased as I continued trying different wiring combos, testing again after each combo failed to work).

 

Is it likely that this sending unit just isn't compatible with this gauge? Am I missing some obvious wiring solution? (not an engineer myself if you haven't already guessed)

Could I save myself time and chin scratching by buying a new gauge and sending unit that I know will work together? 

 

Any help would be grand!

 

Many thanks.

 

P.s I've already looked for some sign of a manufacturer on the sending unit and can't see anything but a long number that appears to be of no Google-able significance. 

That number is: 1VT1 7AB327F 15

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5 minutes ago, Fenny_Compton said:

Hello all,

 

I've recently installed a fairly new Lister LPW3 replacing an old one of the same model that was beyond repair.

I've come to link up the Temp gauge and found that I have two spades on the temp sender, to be honest I can't recall whether my last one had two or not, but I've tried every combination I can conceive to try and get the Temp gauge to show something but no, nothing.

 

Now, my temp gauge was on the boat when I bought it and a quick Google has lead me to find an identical looking one here on Amazon, which leads me to believe it's a cheap pile of sh*te. But that gives you an idea for the wiring, one pos, one neg and one single sender cable. Also worth noting it seemed to work fine on my previous engine.

 

I've tried the sender cable on both spades of the sending unit and tried putting and earth cable on the opposing spade simultaneously, then tried a live lead from the ign. accessories and still nothing. 

 

I checked the sender unit by putting a multimeter on the spades set to ohms and found it does appear to be working (although I didn't test it methodically, I just noted it was reading something after being run for 15-20mins and the number slowly decreased as I continued trying different wiring combos, testing again after each combo failed to work).

 

Is it likely that this sending unit just isn't compatible with this gauge? Am I missing some obvious wiring solution? (not an engineer myself if you haven't already guessed)

Could I save myself time and chin scratching by buying a new gauge and sending unit that I know will work together? 

 

Any help would be grand!

 

Many thanks.

 

P.s I've already looked for some sign of a manufacturer on the sending unit and can't see anything but a long number that appears to be of no Google-able significance. 

That number is: 1VT1 7AB327F 15

 

 

 

 

There are only two common sender/gauge standards and if they are wrong the gauge either reads twice what it should or about half.

 

Make sure the positive, negative and sender cable are on the correct gauge terminals.

 

At the sender end    with the ignition on, earth the gauge wire to the block. The gauge should go to full deflection. If not, it's probably a wiring fault.

 

The two terminals might be gauge and negative connections or sender and overheat warning. As you say you gave a falling resistance  as the engine heated up I suspect its sender and negative. In any case, if this is wrong, you are unlikely to damage anything. Try the gauge to one terminal and connect the other one to the engine block. I suspect it will work, but report back.

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I,ve  just replaced the sender on my Perkins 4108M and from the stockist there was an option of 1 or 2 spades. My engine is a full marinisation from Perkins, and all parts are 'cable  earthed'. Is it possible that there may not be a path through the block and that you need a full dedicated cable? 

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It looks like the normal lister temp warning switch which is 2 terminal, one to negative the other to the warning light. That doesn't seem consistent with what you found though. 

In my experience the lister temp warning switches are not the most reliable things. Might be worth testing by heating it up off the engine.

 

Eta might be worth just ordering a cheapo gauge and sender off ebay. You need a 1/8 npt size sender. 

Edited by jonathanA
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6 hours ago, Tony Brooks said:

 

There are only two common sender/gauge standards and if they are wrong the gauge either reads twice what it should or about half.

 

Make sure the positive, negative and sender cable are on the correct gauge terminals.

 

At the sender end    with the ignition on, earth the gauge wire to the block. The gauge should go to full deflection. If not, it's probably a wiring fault.

 

The two terminals might be gauge and negative connections or sender and overheat warning. As you say you gave a falling resistance  as the engine heated up I suspect its sender and negative. In any case, if this is wrong, you are unlikely to damage anything. Try the gauge to one terminal and connect the other one to the engine block. I suspect it will work, but report back.

 

Thanks everyone, here are my findings so far:

 

1. All wires are correct, i.e pos, neg and sender from gauge. 

2. Touched temp gauge sender female spade to engine block and it went to full deflection, so I know that's working.

3. Made sure I have a negative connected to the engine block and then touched that neg to the gauge sender wire and again full deflection so I know they're both working!

4. Next I connected them up to the sender unit and made a link across the two spades with a spanner which caused full deflection.

5. Swapped them over to see if they would or wouldn't work the other way around but they still made full deflection so didn't really answer that question of which spade is which.

6. Lastly, I unscrewed the sender unit (photographed below if you're interested) and held the end in some boiling water whilst being fully wired up, nothing from the gauge!!

7. Swapped the spades around, re boiled the water and tried it again, NOTHING from the gauge!!

 

Does this confirm that the sender is funked? Or perhaps that it just isn't compatible with this gauge?

As mentioned in an earlier post when I hooked it up to an ohms meter after running the engine I got readings which would suggest it worked. 

 

The plot thickens! Thanks for your help all.

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UPDATE!

 

Soooo when putting the sender back in it suddenly became all too easy to screw in... and seems to have sheared off.

I'm always extra careful not to over tighten so perhaps this is the reason why it wasn't working in the first place? (I'd like to tell myself that at least)

 

So I guess the solution is much simpler now, get a new one!

Is it worth me just getting a one spade sender now rather than a 2? And can anyone recommend any decent brands for quality sender parts?

 

Thank you all!

 

 

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The sender has to match the gauge, see my earlier post. The thread size often ensures you get the right one but yours is fitted in an adaptor so unless you can identify the gauge maker and post it in case anyone knows if it's US or European you may have to but the gauge and sender to be sure they match.

 

Some Listers have a fancy solenoid system so they run as insulated return, so if yours is one of those you will need a two blade sender. If not, then a single blade should do.

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I did say the lister senders were a bit crap I've had one do the same and also one were one of the terminals broke off...

As i said before you need a 1/8 NPT thread sender the gauge you linked to has a metric sender.

 

Yours was screwed into an adapter I think from 1/4 NPT to 1/8. There are some some other  places to fit temp senders/switches on the lpsw and I can't quite work out where yours is. (Not that it matters). Find a gauge with a 1/8 sender and you will be OK. 

 

Do you have a temp warning light on your control panel as well as the gauge ?

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11 hours ago, Fenny_Compton said:

hmm yes I see. Well mine looks identical to this one on Amazon front and back, and that says it's 'universal' so is it better to get a new gauge and send to be sure?

 

Cheers

Universal means nothing. As @Tony Brooks said, there are two common standards and the sender and gauge must match. This is one of those situations where buying from a known quality specialist supplier, rather than no-name stuff from Amazon, or the Bay will be a good idea. Buy cheap, buy twice and all that. Suppliers of marine parts, ASAP supplies etc. Also worth looking at people who supply to the specialised vehicle market. Get a gauge with a matching 1/8NPT sender.

Jen

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12 hours ago, Fenny_Compton said:

hmm yes I see. Well mine looks identical to this one on Amazon front and back, and that says it's 'universal' so is it better to get a new gauge and send to be sure?

 

Cheers

Looks like it will work, provided the sender thread matches the block.

Better to buy that than mess about trying to get a sensor that matches the gauge you have.

 

ETA it says it's a 10mm thread so could be problematic you will need an adapter to match the block thread

Edited by Loddon
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When I replaced mine, it was with a 3/8" thread and a bush instead of 1/2". The only thing I did, being a clever boiler engineer, was to bleed the bush after installation. The gauge gradually crept up and up. I had introduced a 'dead leg' into the unit. Drained it out and all worked well .

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Thanks for the help everyone.

 

I do have a gauge and a warning light, would any dual sender like this work both or would I need something explicitly for a warning light and gauge?

I’m not massively fussed about the warning light as long as I have a working gauge.

 

In terms of the ‘NPT’ is ‘NPTF’ the same thing? That’s all I can see ASAP-Supplies do in a 1/8 size. I was looking at this specifically just for the single gauge route.

 

thanks all!

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Engines like old Listers with piston oil pumps don't like electric senders, the pump pulses tend to make them leak after a while. Capilliary tube gauges ok.

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25 minutes ago, Fenny_Compton said:

Thanks for the help everyone.

 

I do have a gauge and a warning light, would any dual sender like this work both or would I need something explicitly for a warning light and gauge?

I’m not massively fussed about the warning light as long as I have a working gauge.

 

In terms of the ‘NPT’ is ‘NPTF’ the same thing? That’s all I can see ASAP-Supplies do in a 1/8 size. I was looking at this specifically just for the single gauge route

 

thanks all!

 

How many more times - the sender and gauge have to match. Is your gauge a European one or a US standard one? The senders you link to are Euro ones. You do not need a dual station/gauge sender, they are for  flying bridge cruisers with an inside and outside helm position.

 

I think that you have an overheat switch for the lamp somewhere else on the engine.

 

 

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@Tony Brooks Please feel free to take a look here and give me your best guess because it just says 'Universal' on the advert and I have no paper work to tell me otherwise. 

 

So I'm looking to get a new sender and gauge so I know they match. But ASAP-Supplies seem to only do NPTF senders and I'm told here that I need NPT. So will have to look elsewhere I guess!

 

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11 minutes ago, Fenny_Compton said:

But ASAP-Supplies seem to only do NPTF senders and I'm told here that I need NPT.

NPT and NPTF are almost identical. Thread pitch, taper and so on. The only difference is in the crests and root of the threads, where they come to points rather than be rounded off. NPT are designed to seal with a bit of sealant to fill the slight gaps at the crests and roots. NPTF are designed to seal by deforming at the crests and roots slightly as the taper comes together, without sealant. For an engine, you should be able to use an NPTF threaded sender.

Jen

14 minutes ago, Fenny_Compton said:

it just says 'Universal' on the advert and I have no paper work to tell me otherwise. 

Universal is meaningless. Especially in an Amazon lsting from a third party vendor. There are two main standards for resistance ranges for gauges, so there cannot be a universal part that can meet both. The listing is telling porkies.

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6 minutes ago, Jen-in-Wellies said:

NPT and NPTF are almost identical. Thread pitch, taper and so on. The only difference is in the crests and root of the threads, where they come to points rather than be rounded off. NPT are designed to seal with a bit of sealant to fill the slight gaps at the crests and roots. NPTF are designed to seal by deforming at the crests and roots slightly as the taper comes together, without sealant. For an engine, you should be able to use an NPTF threaded sender.

Jen

Universal is meaningless. Especially in an Amazon lsting from a third party vendor. There are two main standards for resistance ranges for gauges, so there cannot be a universal part that can meet both. The listing is telling porkies.

 

Thanks @Jen-in-Wellies, that's the problem with the current gauge, I can't seem to find out whether it's US or Euro so best to get a new sender and gauge I figure.

 

Thanks also for the NPT/NPTF clarification. I'll likely go for a single 1/8 NPTF sender with accompanying gauge both working in matching regions.

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1 hour ago, Fenny_Compton said:

@Tony Brooks Please feel free to take a look here and give me your best guess because it just says 'Universal' on the advert and I have no paper work to tell me otherwise. 

 

So I'm looking to get a new sender and gauge so I know they match. But ASAP-Supplies seem to only do NPTF senders and I'm told here that I need NPT. So will have to look elsewhere I guess!

 

 

Jen has said all that needs saying. I am not going to guess when there is insufficient information. Why oh why do people keep on believing advertising from unknown outfits, often from outside the UK so there is no protection from UK consumer legislation.

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Cheers all for your help on this.

 

I’ve since bought a new gauge and sender from a known manufacturer and they have worked a treat! Wouldn’t have known the size or regional matching was a thing without this education. 
 

Many thanks for all the wisdom! 

 

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