Gauges

[Gadgetman]

How can I tell the difference between a bi metal temp gauge and a semi conductor one, I have a few on the shelf but not sure which is which!

[NonMember]

Do you mean the gauge or the regulator? I've not heard of semiconductor gauges (at least, not for our cars).

To test the regulator, connect a fully charged battery to the B pin, a low power bulb to the G pin, and common all the grounds. A semiconductor regulator will light the bulb dimly. A bimetallic one will make it flash.

To tell a bimetallic gauge from a moving magnet one, connect a 6V battery across it. A bimetallic will slowly creep upwards, while a moving magnet will flick straight to the middle.

[Pete Lewis]

or give the gauge a good shake the moving iron non stabilised needle will wag about the bimetal needle wont move 

Pete

[Gadgetman]

26 minutes ago, Pete Lewis said:

or give the gauge a good shake the moving iron non stabilised needle will wag about the bimetal needle wont move 

Pete

Thanks Pete

the needle flips around as I rotate the gauge so I guess it’s no stabilized then ( gauge number TC4303/03)

[Pete Lewis]

if you use a non stabilised temp gauge you must use 121997  sender   were as stabilised use GTR108 

the fuel float is also very different  you cant intermix senders and gauges 

all ok if used in matched system pairs 

Pete

[Gadgetman]

6 minutes ago, Pete Lewis said:

if you use a non stabilised temp gauge you must use 121997  sender   were as stabilised use GTR108 

the fuel float is also very different  you cant intermix senders and gauges 

all ok if used in matched system pairs 

Pete

Thanks Pete 

this is the temp gauge 

[ahebron]

The numbers on the dial just under the shroud if a 1/2 gauge display will begin with BT if it is a bimetal that runs with a voltage regulator. If its a fuel gauge then it is BF.
All found in attached document at the end.

https://www.revingtontr.com/productimages/docs/00001735/is0011-fuel-gauges-and-sender-units-issue-3-5925692.pdf

Adrian

 

[PatK]

Hi all, Is there any way to test a Vitesse 2L water temperature gauge out of the car?  I'm not sure if it is the sender or the gauge. I have connected a small 9V battery across the gauge terminals but nothing moves so I'm guessing that it is dead. Also is there an ohm meter reading across the terminals to check this? Any help would be most appreciated as usual.  

Thanks       Pat

[Pete Lewis]

the easiest test is just short the sender wire to earth will give a quick full scale sweep 

there is a smiths test box  I have one  , not used much these days 

look out for one of these 

[Colin Lindsay]

https://www.ebay.co.uk/itm/Smiths-Industries-Automotive-Instrument-Tester-SR-D-380/193754669670?hash=item2d1cada266:g:kykAAOSwloxfs~dK

 

Your pic didn't load Pete so I found another, but at that price I'll settle for two lengths of wire and a good earth point.

[NonMember]

4 hours ago, PatK said:

I have connected a small 9V battery across the gauge terminals but nothing moves so I'm guessing that it is dead.

Maybe. The gauge should certainly react to 9V, assuming your battery wasn't worn out. The gauges are not like voltmeters and a tired PP3 may struggle with the current draw, or you may not have been able to make good contact for long enough.

[JohnD]

The gauge is a simple ammeter, that measures the current in a circuit that is modulated by the sensor.      The sensor is a "negative temp coefficent" device that, unlike most conductors, decreases its resistance as temperature rises.   Thus, as the engine heats up, the current through the sensor rises and the indicator needle on the guage moves to the top end.

A PP3 might not deliver enough current to move it all the way, but it should move!      You need a multimeter, Pat, that will measure the resistance inside the gauge.    Not expensive, a tenner or less.     

I suspect that a connection is broken or corroded inside, and that the multimeter would show that there was no connectivity across it.   Another way would be to wire a 12V lamp in series with the gauge and battery.      If it even glows there is a connection through the gauge, and thr fault is something else.      For instance there is a mechanical connection between the coil that senses the current and the needle.    Either way, you loose nothing by trying to take it apart and see!

Good luck!

John

[PatK]

10 hours ago, NonMember said:

Maybe. The gauge should certainly react to 9V, assuming your battery wasn't worn out. The gauges are not like voltmeters and a tired PP3 may struggle with the current draw, or you may not have been able to make good contact for long enough.

Thanks Rob, it was a new pp3 9V, and I had very good contact with the battery and terminals, would I damage it if I connected the car battery directly to it?  The last couple of times that I ran the engine it did not work at all, so I will first check the sender as Pete says. Thanks.    Pat

[Colin Lindsay]

You don't need the sender; it's just the bit that controls the movement of the needle on the gauge. Earth the sender cable to the car engine block and the gauge should move fully across. It's designed to work on 12v so you won't do it any harm unless you get the wires back to front, and even then some gauges will only register zero without harm.

[PatK]

1 minute ago, JohnD said:

The gauge is a simple ammeter, that measures the current in a circuit that is modulated by the sensor.      The sensor is a "negative temp coefficent" device that, unlike most conductors, decreases its resistance as temperature rises.   Thus, as the engine heats up, the current through the sensor rises and the indicator needle on the guage moves to the top end.

A PP3 might not deliver enough current to move it all the way, but it should move!      You need a multimeter, Pat, that will measure the resistance inside the gauge.    Not expensive, a tenner or less.     

I suspect that a connection is broken or corroded inside, and that the multimeter would show that there was no connectivity across it.   Another way would be to wire a 12V lamp in series with the gauge and battery.      If it even glows there is a connection through the gauge, and thr fault is something else.      For instance there is a mechanical connection between the coil that senses the current and the needle.    Either way, you loose nothing by trying to take it apart and see!

Good luck!

John

Thanks John, that is great advice, infact I do have a couple of multimeters, so should I check for resistance across the terminals, and if resistance is infinite, I guess that something is broken inside, but  I also like your practical light bulb test and will also try that first. Your explanation of how it works is great, so if it is kaput I will take it apart, and the good news is that I do have a miniature soldering iron suitable for printed circuits, so that will do the job. Thanks again John.  Pat

[Pete Lewis]

14 hours ago, Colin Lindsay said:

but at that price I'll settle for two lengths of wire

crikey   i have a cupboard full of gold 

Pete

[Colin Lindsay]

 

Just now, Pete Lewis said:

crikey   i have a cupboard full of gold 

Pete

See? 2021 is brill already!

[NonMember]

12 minutes ago, PatK said:

would I damage it if I connected the car battery directly to it?

If it's an original type gauge (later model with voltage stabiliser) then it's a bi-metal strip with a heating coil. It's not polarity sensitive and it'll cope with 12V across it no problem. If it's the earlier (no stabiliser) type then it may be polarity-sensitive but is designed for 12V so again, no problem.

[PatK]

2 minutes ago, Colin Lindsay said:

You don't need the sender; it's just the bit that controls the movement of the needle on the gauge. Earth the sender cable to the car engine block and the gauge should move fully across. It's designed to work on 12v so you won't do it any harm unless you get the wires back to front, and even then some gauges will only register zero without harm.

Thanks Colin, I will give that a go.  I was very impressed with your details of how you are attempting to cure the tub sag in your Herald convertible. I have exactly the same problem with my vitesse and I have just bought two 5"wide very heavy ratchet straps, and wii have a go in the New Year. Like yours it is the offside that is worse, but if mine keeps springing back like yours, then I will grind the paint off at the bottom and apply heat as the first measure. Thanks Colin.  Pat

[PatK]

11 hours ago, NonMember said:

Maybe. The gauge should certainly react to 9V, assuming your battery wasn't worn out. The gauges are not like voltmeters and a tired PP3 may struggle with the current draw, or you may not have been able to make good contact for long enough.

Thanks, yes I'm afraid that you are probably right, but with the great advice given here I will attempt to repair it if its broken. Thanks.   Pat

[Pete Lewis]

its harder to pull a CV tub in as the rear deck is longer than on a saloon 

we had to pull in inches to gain 1/2" on spring back  

if you go too far you may jam the boot lid /width 

Pete

[PatK]

3 minutes ago, NonMember said:

If it's an original type gauge (later model with voltage stabiliser) then it's a bi-metal strip with a heating coil. It's not polarity sensitive and it'll cope with 12V across it no problem. If it's the earlier (no stabiliser) type then it may be polarity-sensitive but is designed for 12V so again, no problem.

Thanks very much, yes its a later model with voltage stabiliser, so I will try 12v acrostic.  Thanks.   Pat

[PatK]

1 minute ago, Pete Lewis said:

its harder to pull a CV tub in as the rear deck is longer than on a saloon 

we had to pull in inches to gain 1/2" on spring back  

if you go too far you may jam the boot lid /width 

Pete

Words of wisdom, thanks Pete, but I reckon it would be far easier to jack it back out if its too far in! Good thought about the boot closure though. Thanks Pete.    Pat

[PatK]

15 hours ago, Pete Lewis said:

the easiest test is just short the sender wire to earth will give a quick full scale sweep 

there is a smiths test box  I have one  , not used much these days 

look out for one of these 

Thanks Pete, so I'm looking for a white square with a question mark in the middle? I think that there was one on e bay last night. I will buy it if its still available!  Thanks Pete.  Pat

[Pete Lewis]

there will be a lot of creak cracking going on  you need to keep any eye on the deck as it can start to buckle 

something has to give , i know not what