Midget Gauges

[stephenh 671]

I have just been in touch with Moss Europe about replacing my auxiliary gauges, as those who followed my build thread closely may recall I had a lot of trouble with my fuel gauge in particular. If you wanted nice shiney new looking gauges, the procedure used to be that they were only available on an exchange basis, reconditioned, or of course you could recondition them yourself if you had the know-how to do so.  Well ,now it turns out that some one has acquired the right to use the Smiths name on these dashboard gauges, and is having them made new, as reproductions of the originals. So no longer reconditioned on an exchange basis, and the price isn't much different to the reconditioned items.

I thought I'd post this as it might help someone else planning a build, or refurbing an older car.

The other point which is connected, is that if you are guided by the picture in the factory build manual as to which of the fuel gauge senders to get, if buying new, you may end up making the same mistake as me. The picture in the build manual most closely resembles the very early sender, as fitted to frogeyes and early MK1 Midgets, and early MK II Sprites. These cars had positive earth electrical systems,  whereas the gauges from a MKIII Midget would be on negative earth cars. I think this is why I've always had problems trying to get my fuel gauge to work. I've now ordered a new gauge (having I think blown the old one) and a new sender unit to match it.

[Simon Marks - North Oxfordshire AO 169]

Hi, Stephen,

I just replaced my instruments (and sender) when I built my car as I found the gauges in the Moss Europe catalogue.  Nice, shiny new instruments to match the speedo / tachometer which I had refurbished by Caerbont in South Wales.  No problems with getting everything to work and they have been reliable since.

Simon

 

[wizzer 106]

Not sure if this applies to you but my old smiths gauges had to have 10v supply to make them work properly . 

Tony 

[stephenh 671]

12 volts should be ok on these, Tony, because all the Midget batteries were 12 volt.

[Dave Eastwood (Gadgetman) - Club Secretary 4,637]

11 hours ago, stephenh said:

12 volts should be ok on these, Tony, because all the Midget batteries were 12 volt.

- But did the Midgets have a Voltage regulator to supply the instruments?

Modern electronic instruments don’t usually need a regulated feed, but it’s not uncommon on older/classic vehicles.

Vehicle electrics that are shown as being 5 Volt or 10 Voltare often classic examples of something expecting a regulated supply.

[Simon Marks - North Oxfordshire AO 169]

Hi, Dave,

The Eleven wiring loom allows for the regulator to be fitted - also available from the likes of Moss Europe.  Mine has this.

Simon

[stephenh 671]

Hi Simon, I thought that the regulator was only needed if you wanted to use an old dynamo rather than an alternator with its own built in regulator? I had details from Mark Walker of how to adapt the loom so as to obviate the need for a separate regulator if I was using an alternator (and I can't think of any reason why anyone would want to use a dynamo!)

[jonjh1964 387]

6 hours ago, stephenh said:

Hi Simon, I thought that the regulator was only needed if you wanted to use an old dynamo rather than an alternator with its own built in regulator? I had details from Mark Walker of how to adapt the loom so as to obviate the need for a separate regulator if I was using an alternator (and I can't think of any reason why anyone would want to use a dynamo!)

I got the same instructions and use the alternator regulator rather than the old Midget setup

[stephenh 671]

Well now I'm really confused. I have purchased from Moss the negative earth MkIII Midget fuel sender unit which came today. It has 3 spade type terminals. The middle one looks like it is an earth, as it comes with a short black lead (with a bare tail) attached already to the middle spade.But which of the other 2 terminals do i use? I have a wiring diagram for the later (negative earth) Mk III, but it only shows one lead from the gauge to the sender, and then the sender in turn going to earth.

Also just to muddy the waters over what I said earlier in regard to regulators, the wiring diagram shows a "bi-metal instrument voltage stabilizer" in line, between the live feed from the fuse box to the fuel gauge, but on the earlier positive earth wiring diagrams no such stabilizer! 

[wizzer 106]

36 minutes ago, stephenh said:

Well now I'm really confused. I have purchased from Moss the negative earth MkIII Midget fuel sender unit which came today. It has 3 spade type terminals. The middle one looks like it is an earth, as it comes with a short black lead (with a bare tail) attached already to the middle spade.But which of the other 2 terminals do i use? I have a wiring diagram for the later (negative earth) Mk III, but it only shows one lead from the gauge to the sender, and then the sender in turn going to earth.

Also just to muddy the waters over what I said earlier in regard to regulators, the wiring diagram shows a "bi-metal instrument voltage stabilizer" in line, between the live feed from the fuse box to the fuel gauge, but on the earlier positive earth wiring diagrams no such stabilizer! 

This was my fuel sender it had two connections ground and 12v 

Think it was from a triumph ,the gauge on my dash was above the full Mark when I filled the tank so I fitted a 10v regulator and it made it read correct also my water temp was always high and the regulator made that read correct to ,the water temp was a single wire to the sender , sounds like your fuel sender has ground, 12v and signal wire, is that how a more modern gauge would work, 

Tony

[stephenh 671]

Mine doesn't look anything like yours, Tony.

However, I'm thinking that I may (only may, mind you) have answered my own question about the 3 spade type terminals. Possibly the third one is for an optional low level warning light? But if so, which is which?

I'll have a look at the later, MkIV, wiring diagram and see if that helps at all. 

[stephenh 671]

Well having looked at the later Midget wiring diagrams, even the USA and California versions, I'm none the wiser, as they all seem to show only 2 connections to the sender, namely earth and the live feed to the gauge. I'll have to have a play with my multimeter, although that always make me nervous as I don't pretend to be very clued up when it comes to car electrics. 

Edited to add: Just spoken to someone at Moss, to order a voltage instrument stabilizer. I also asked about the 3 terminals on the tank sender unit. As I suspected, the 3rd. terminal is for a low level warning light. These weren't normally fitted to Midgets, but the same sender is now used on various cars, for example on an MGB, and they probably did have a warning light. Now I look closely, one of the bare male spades has WL cast into the nylon body of the sender, and the other has I, adjacent to it. I goes to the gauge so is live, and WL would go to a warning light, so in my case I can ignore it. Thought I would post here in case this is of help to others who want to use this sender.