Temp guage issues

[kiwi-jim]

Havng done the start up I am now trying to get the temp guage to work, I don;t have the original capillary type guage but I have one from a tr4 and one from a 3a (i believe) both electric. I have wired them up via a new voltage stabiliser and nothing is happening. Basically is there a test to ensure the guage itself is working. I have tried with both guages connected into the car and the sender (new one) sitting in hot water, and there isn;t a flicker of movement. other than a wee flicker when you turn the ignition on and nothing else.

 

I am wondering is it the guages (if so how do I test them) or have i made another mistake. Any suggestions appreciated

[TR 2100]

No such thing as an electric TR3 temp gauge, not even

on the 3B.

 

Is your TR3 Pos or Neg earth? TR4 gauges were designed

to operate with Neg earth.

 

AlanR

[kiwi-jim]

That could help explain the problem as I am still positive earth, how can I resolve that By repolarising everthing is that the only way??

[TR 2100]

That could help explain the problem as I am still positive earth,

how can I resolve that By repolarising everthing is that the only way??

 

My understanding of electrics is such that I don't even know

if this makes a difference or not, or what you could do about

it. I just guessed it could be a factor.

 

I'm sure someone will give you the details.

 

AlanR

[Alec Pringle]

" TR4 gauges were designed to operate with Neg earth."

 

The TR4 utilised a positive earth electrical system, so how were the gauges so arranged ?

 

Cheers,

 

Alec

[John390]

Short the wire going to the sender unit to ground (engine block). That should make the guage show full scale, if it does it indicates a faulty sender. That would be my first test. If you have a new votage stabilizer have you checked the voltage going into it and the voltage coming out that connects to the guage?

You should still be able to use the TR4 guage. You said that it slightly moved up when you turned the ignition on, a good sign.

 

Cheers John

Edited August 17, 2010 by John390

[vivdownunder]

Jim, you probably have an early TR4 domed glass elec temp guage. The other one could be the later TR4 temp guage with flat glass.

 

The TR4 domed temp guage only has half the needle showing whereas TR2-3B guages have the whole of the needle showing.

 

I have an electric sender with the TR4 domed guage and didn't need to change it when I swapped from positive to negative earth.

 

With John's ideal test, when you short the sender wire, just check for a spark to prove there's no break in the wire.

 

Regards,

 

Viv

[TR 2100]

" TR4 gauges were designed to operate with Neg earth."

 

The TR4 utilised a positive earth electrical system, so how were the gauges so arranged ?

 

Cheers,

 

Alec

 

Alec - you're right. Early TR4s were Pos earth.

Senior moment.

 

AlanR

[Badfrog]

Alec is right but when I turned L.A. from pos- to neg- earth, around 1978, all I had to do was to invert the battery cables and the ammeter wires and start the engine for instant no-fuss dynamo repolarisation. Other gauges just did not care.

 

These gauges are the original late TR4 flat glass combo (Smiths and Lucas) as befits a '63.

 

Of course you also need a good 10V stabilizer on a TR4, which does not exist on TR3s. I always wondered how TR3 managed that voltage stabilizing. May be they don't and use 12v gauges?

 

I am currently installing water temp and fuel gauges (from a long dead TR4) on the A7. 12v, neg- earth, no stabilizer there. I'll post if any interesting symptom appears.

 

Badfrog

[vivdownunder]

Badfrog, TR2-3B's had the alcohol filled capillary temp sender that didn't need power, and we just accepted the fuel guage was as erratic as a mad woman's hairdo.

 

I only realized what an improvement the voltage stabilized fuel and electric temp guages were when I eventually got a TR4.

 

Thus a stabilizer and elec temp guage is a discreet improvement on the 3A. I fitted a TR4 tank sender and it's great. There's still plenty of fuel when reading empty, so it's like having a reserve tank.

 

Incidently, as far as I know, the alcohol filled capillary wasn't single malt, so useless for a quick swig if desperate.

 

Regards,

 

Viv.

[kiwi-jim]

Hi guys thanks for the replies I will try out Johns short method just to check the sender isn't a dud. Viv it you have put a tr4 guage into a tr3 with a voltage stabilizer can you send me/ describe the wiring diagram, just to check i havn't stuffed it up. I have looked at the various tr3 and tr4/5 wiring diagrams( that use a stabilizer in the system) I can find and wired it the way looks right/makes sense to me. maybe I have stuffed it up in some way.

The guages I have available to me i have rechecked against all the available photos in books etc I can find, Both are 1/2 needle showing guages one is a jaegers that looks like/resembles the type shown in Tr5s/tr250s. The other is a smiths guage thats out of something else I now realise ( but it looks good and hs the dombed glass). Basically both are temp guages that untill i can get an original should/could be made to work.

If only they would.

Not keen to run the car gain till I have a functioning temp guage so all help is hugely appreciated. I'll let you know john how your suggested test works out.

thanks.

[Badfrog]

Badfrog, TR2-3B's had the alcohol filled capillary temp sender that didn't need power, and we just accepted the fuel guage was as erratic as a mad woman's hairdo.

Viv.

 

 

Of course !! Like my 122S. How stupid of me...

 

Badfrog

[kiwi-jim]

,

I tried johns suggestion and shorted the sender wire against earth and the Gauge shot up to max so it would seem the sender unit is faulty even though it was a new one. Is there a chance however there could be another answer???

If the sender was not the correct one for the gauge could that be part of the problem . ie will a sender work with any electric gauge in some way shape or form provided it isn't broken.

 

Basically I can't be sure the sender is totally correct for the gauge.

cheers

[MikeF]

,

I tried johns suggestion and shorted the sender wire against earth and the Gauge shot up to max so it would seem the sender unit is faulty even though it was a new one. Is there a chance however there could be another answer???

If the sender was not the correct one for the gauge could that be part of the problem . ie will a sender work with any electric gauge in some way shape or form provided it isn't broken.

 

Basically I can't be sure the sender is totally correct for the gauge.

cheers

 

 

 

HI

On my early 4 the needles are naked as on the 3. The electric temp gauge is calibrated in F with 185 at the central (lowest position) on the scale. As already remarked later gauges have shrouded needles and gauge scales became progressively less informative).

Although the early 4 gauges look like those from the 3, including the domed glass, the temp and fuel gauges work differently (basically hot wire devices) but are not polarity sensitive. As they are voltage dependent you will need a voltage stabilizer.

 

If when you tested by shorting you disconnected the wire at the sender end, then you have tested everything but the sender, so that is kind of telling you it’s the sender.

 

Just a stupid question though before you send it back: where is the sender on your car? The body of the sender has to be earthed to the engine. I only ask because I have no idea what the arrangement on a TR3 is except that that would not be a requirement for the 3 sender to work.

 

 

 

Mike

[kiwi-jim]

Hi Mike

The sender on the TR3 is fitted into the Thermostat housing This is the same in the TR4/4a so I assume it gets a proper earth through that. One question no one can answer for me so far is does the sender HAVE to match the Gauge. ie will another sender from another model work even if the gauge just reads wrong, or will a gauge with a different sender attached just not work at all. I know realise the gauge I have is not an original TR gauge, its of the era, etc but what it is from I am unsure of. Any thoughts

[stuart]

Hi Mike

The sender on the TR3 is fitted into the Thermostat housing This is the same in the TR4/4a so I assume it gets a proper earth through that. One question no one can answer for me so far is does the sender HAVE to match the Gauge. ie will another sender from another model work even if the gauge just reads wrong, or will a gauge with a different sender attached just not work at all. I know realise the gauge I have is not an original TR gauge, its of the era, etc but what it is from I am unsure of. Any thoughts

 

Senders have different resistance values going from low to high or vice versa depending on the gauge so it may be an idea to try another sender. TR5/6 cylinder senders are often supplied wrongly and cause many worries over false overheat readings. Measure the resistance of the sender cold and then put it in some boiling water and measure then

Stuart

Edited August 22, 2010 by stuart

[kiwi-jim]

Thanks Stuart, i'll measure the resistance as you suggest but how will that help me, is that to determine just that the sender is either working or not depending on whether the resistance changes.

Is there a way to match the resistance of a particular sender to a gauge to ensure you have the correct one.

cheers jim

[stuart]

Thanks Stuart, i'll measure the resistance as you suggest but how will that help me, is that to determine just that the sender is either working or not depending on whether the resistance changes.

Is there a way to match the resistance of a particular sender to a gauge to ensure you have the correct one.

cheers jim

 

That was really just to establish if the sender is doing anything as it seems your gauge is ok. Dont know any way of cross referencing senders to gauges other than finding out how much resistance it would take to actuate the gauge across the range.

Stuart.

[johnny250]

... I have tried with both guages connected into the car and the sender (new one) sitting in hot water, and there isn;t a flicker of movement....

 

 

Hi Jim, what happens to the gauge when the sender is fitted to the car and rad water is hot?

it won't work by just dangling it in hot water without the ground connection

 

john

[kiwi-jim]

Hi John

yes i tried the sender in hot water with an earthed wire wrapped round the threads, and nothing happened, with the car running, sender back in and an external thermometer sitting in the header tank(neck) part of the Rad, showing 140 def F , there is still no reading either. I assume now it is the sender based on all the replies so I will first try Stuarts resistance theory and look to try another sender to see how we get on. I have a mates TR4a sitting in my garage at the moment so he might loose his sender for an hour or two, luckily hes not on this forum so he will never know.

Cheers Guys