Fuel & Temperature Gauges - Series 2

vaultsman

Well-Known Member
#1
I finally got around to fitting my recalibrated speedo last week and all seems fine. :D

However, after fitting, I found that the fuel and temperature gauges weren't registering at all. :evil:

So, it's either something I've disturbed in the instrument panel or, coincidentally, something like the voltage regulator has packed up.

I've swopped the gauge for a spare I've got but still no joy. The spare was untested, and I can't vouch for whether its OK.



The spare gauge is on the right and has a capacitor fitted which, interestingly, my existing gauge doesn't have. The existing gauge has been taken out in the past by a previous owner as there were traces of Blu-Tak in the mounting screw slots.

The car has been off the road since last October, but the existing gauges were working fine when last used.

I'm assuming I should be able to check on the panel printed circuit board for 12V with ignition on? And where should I be checking on the gauge PCB for continuity, etc?

Any ideas all?
 

vaultsman

Well-Known Member
#3
Thanks Rich,

I'd like to prove one way or another whether either or both of the gauges I've got are OK or not.

So if you've got a proven gauge set I could pop in to try, that'd be more than useful.
 

colnerov

Well-Known Member
#4
Hi, I would say it is the switch contacts in the voltage stabiliser have furred up. Try getting
inside and cleaning them with emery. A while ago Practical Classics did a quick feature on an
electronic one which I posted on another thread, If you want I will post it up again. Other than
that try measuring the resistance across the gauge, I am not sure offhand what it should read
but anything other than open circuit is promising.

Colin
 

arthuy

Well-Known Member
#5
I would need to check but think there is a single white wire with black boot which goes on that stump next to your voltage regulator. Or similar.

Been a while.
 
#6
arthuy said:
I would need to check but think there is a single white wire with black boot which goes on that stump next to your voltage regulator. Or similar.

Been a while.
It does look like there is no wire going to that post in the picture, but can't be sure. At any rate, measure the voltage coming into the reg and the voltage coming out and you will have your answer
 

vaultsman

Well-Known Member
#7
arthuy said:
I would need to check but think there is a single white wire with black boot which goes on that stump next to your voltage regulator. Or similar.

Been a while.
But the gauges were working fine, and I don't think any wires have become disconnected?

OrganDoctor said:
arthuy said:
I would need to check but think there is a single white wire with black boot which goes on that stump next to your voltage regulator. Or similar.

Been a while.
At any rate, measure the voltage coming into the reg and the voltage coming out and you will have your answer
Thanks Dick, unless I'm missing something I can't measure this with the gauge in situ. I've removed the voltage stabiliser from the existing gauge and there are 3 terminals on the base - B, I, and E. I'm assuming E is Earth (?). Would I be Input....maybe?

I get 118 ohms between B & E, and also between I and E. Continuity between B & I.

Before I open it up, I can certainly rig 12V onto the stabiliser and measure the output....which terminals do I rig it to? B & I?

Cheers,

Stan
 

arthuy

Well-Known Member
#8
Had a look at the diagrams. I think the wire I had in mind is the rev counter.

The feed for the voltage regulator comes from fuse 19-20. The same supply feeds the oil guage before the VS. If the oil guage is working then the supply will be ok.

It may go to the flasher unit first.

Colin
 

vaultsman

Well-Known Member
#9
arthuy said:
Had a look at the diagrams. I think the wire I had in mind is the rev counter.

The feed for the voltage regulator comes from fuse 19-20. The same supply feeds the oil guage before the VS. If the oil guage is working then the supply will be ok.

Colin
Thanks for that Colin. Yes, I can see the supply for the instruments comes from fuse 19-20 to connect onto the panel PCB. My concern was whether I'd somehow damaged the panel PCB tracks in the area of the fuel/temperature gauge when fitting the speedo.

Oil pressure gauge is working after a fashion, but it's been a temperamental so-and-so for a while which is why I fitted the mechanical gauge. So there's 12V up to that point, but beyond? I'll have another look with the meter in the next couple of days.

I'll also have a play with the stabiliser.
colnerov said:
Hi, I would say it is the switch contacts in the voltage stabiliser have furred up. Try getting
inside and cleaning them with emery. A while ago Practical Classics did a quick feature on an
electronic one which I posted on another thread, If you want I will post it up again. Other than
that try measuring the resistance across the gauge, I am not sure offhand what it should read
but anything other than open circuit is promising.

Colin
Is this the article, Colin? http://www.britishv8.org/articles/mgb-voltage-stabilizer.htm
 

colnerov

Well-Known Member
#10
Hi, Stan, the connections on the voltage stabiliser are as you say E- earth B- ignition supply
I- stabilised output. The article I was referring to was this one although it is all pretty much
the same.-


Colin

PS sorry about the size of the pic I am not clever enough to resize it :oops:
 

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arthuy

Well-Known Member
#11
Any time I have had problems with guages there always seems to be an earth wire in the wrong place or not put back. Fault VS tend to give a higher output or atleast the ones I have came accross have. No output could be faulty unit or faulty earth.

Make up a jumper wire with a male on each end to by pass the guage. They will handle 12v just wont read accurately. But only do it to for a test as long term you could damage them.

Colin
 

vaultsman

Well-Known Member
#12
colnerov said:
Hi, Stan, the connections on the voltage stabiliser are as you say E- earth B- ignition supply
I- stabilised output.

Colin
Thanks Colin, looks interesting. I might have a go at that conversion.

Just double-checking....

B = Ignition Supply, I = 10V Output :?:

Cheers,
Stan
 

vaultsman

Well-Known Member
#15
This is the view of the instrument panel with the Fuel/Temperature gauges out:


Tried all the contact surfaces to see if I could pick up 12V anywhere, but no joy. :evil:

Thankfully I'd got a complete spare binnacle so I pulled all the gauges from that:


I've never been able to fully decipher the plug/pin numbering on my wiring diagrams, so I thought it wouldn't hurt to get them listed. There are 2 13-pin multiplug connections onto the PCB - Plug A is at the top left, and Plug B is right of centre at the bottom. Not all the pins are connected and it seems the plug keyways are at Pin 4 - don't know why, but it took a bit of head-scratching before I realised! :roll:
Others may find the pics useful, so here they are:

Plug A


Plug B


So Plug B,Pin 4 should be putting 12V onto the upper left contact for the voltage stabiliser (mounted on the rear of the fuel/temperature gauge).

And this is why it didn't...


Closer...


Yeah, my fault... :roll: Obviously in the past, the PCB track had fried or got damaged at that point and somebody had repaired it with a jumper cable. Along comes Stan to pop in his shiny recalibrated speedo, didn't spot it, and dislodged it....

Stripped out the damaged PCB...


...and replaced it with the good spare.

I'd opened up and had a look at the original Smiths voltage stabiliser and, to be honest, it seemed fine but I thought I'd have a look at the solid-state ones that Colin put the link up to. Picked up a couple from Maplins for the princely sum of £1.04 each.


Tested it on the battery and the output is a steady 9.85V.

Anyway, everything back together now and all instruments working fine. I'm sure I've got a bottle of that stuff used to repair heated rear windows somewhere, so I'll probably have a go at tickling up the original PCB.

Cheers for all the help, guys!

Stan
 

Mikep

Active Member
#16
By pure coincidence it seems after fiddling with my speedo cable today I too have suffered what appears to be a fuel gauge failure. I was fixing the screws for the binnacle when I realised I was bending the fuel gauge needle :evil: I carefully bent it back and fearing I caused more damage turned on the ignition to find the needle didn't move :( of course there could be some other problem, everything looks ok behind the gauge face, but its interesting to read of you voltage stabiliser problem Stan as it appears to have packed up after moving the cluster about.

Mine appears to be very rusty on the outside as well so it might be worth changing it just to eliminate that component as the cause. I have been on Maplins website, can you confirm if this was the voltage stabiliser you purchased Stan?

http://www.maplin.co.uk/p/ts7810cz-1a-p ... case-n38ca
 

vaultsman

Well-Known Member
#17
Hi Mike,

Yes, that's the correct component.

The 2 voltage regulators I had were similarly both somewhat rusty on the outside, but after opening one up and testing I suspect were both operating OK. However the electronic solution continues to work well with a consistent output.

Interestingly, the temperature gauge now reads a touch lower than previously but, I suspect, more accurately as I'm running a cooler-than-standard thermostat.

Must think about changing that.

Stan
 

Mikep

Active Member
#18
Thanks Stan :D

While I think of it, where did you get your speedo refurbished? Mine has started sticking between sixty and seventy, hence the reason for today's cluster removal. It would appear when gently moving the needle slight resistance is felt at the point it gets stuck :?
 

Mikep

Active Member
#20
Sod's law the fuel gauge works today. I've bought some of those regulators so I may mod the gauge in the future. Thanks for the help Stan.
 
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