• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)
Tips
Tips

TR2/3/3A Fuel gauge readings?

karls59tr

Darth Vader
Country flag
Online
I've installed a TR4 fuel gauge, sending unit and stabilizer in my TR3. I'm also running an alternator and voltage gauge. Battery has 12 volts.When I turn the key on to accessory the gauge needle slowly goes to half way between 1/4 and 1/2 tank and stops. The tank is nearly Full. ( I've got one carb off on the bench so cant start the car at this time.) I was wondering if when the car is running would the extra current from the alternator cause the gauge needle to go the rest of the way up or is there another issues going on here?
 

DavidApp

Yoda
Gold
Country flag
Offline
Can you hook up a battery charger to see if that has any effect.

Not sure what you mean by Stabilizer.

The fuel gauge may need to be adjusted so that it indicates accurately.

David
 

TR3driver

Great Pumpkin - R.I.P
Offline
With reading that low, I'm pretty sure you've got something else going on.

Is the stabilizer an original type (thermal) unit, or an aftermarket solid-state unit? The original type will work correctly all the way down to 10 volts input, but the solid state ones need more voltage. How much more depends on which regulator IC they used inside, the popular LM7810 needs at least 12 volts input to produce 10 volts output.

But even if the input at the stabilizer has dropped somewhat from battery voltage (due to resistance in other places), I would expect the gauge to read only a little bit low. 1/4 tank, maybe, but not 1/2 tank.
 
OP
K

karls59tr

Darth Vader
Country flag
Online
The stabilizer I bought from Moss is the one upgraded to solid state. So your saying that it needs the full 12 volts to produce 10 volts output. I think my problem might be the battery itself. It sat indoors for most of the winter. I had a 1.5 trickle charger on overnight but that did not seem to do the job so I put a 10 charger on for a few hours. I put a tester on the battery and it did read 12 volts but when I put a load on it the dial read "weak"?
I was wondering that if I had the car running the alternator would produce enough voltage for the gauge to read properly?
 
OP
K

karls59tr

Darth Vader
Country flag
Online
Can you hook up a battery charger to see if that has any effect.

Not sure what you mean by Stabilizer.

The fuel gauge may need to be adjusted so that it indicates accurately.

David
I modified my fuel gauge to a the one used in a TR4 because I had one handy and the TR3 gauge had a dead short and was not functional. The TR4 gauge requires a voltage stabilizer so that only 10 volts go to the gauge.
 

sp53

Yoda
Country flag
Offline
You might be able to fix the tr3 gauge, they are kinda interesting inside with these little coils that can be moved around. Perhaps the gauge has cased grounded there.
 

TR3driver

Great Pumpkin - R.I.P
Offline
So, check the voltage coming out of the stabilizer, with the circuit complete (gauge and sender connected). If it is less than 10 volts, then the gauge will probably read higher when the battery voltage comes up (alternator is working).

I still don't think that is the problem (at least not all of it); but if the VS isn't supplying 10 volts, then you can wait and see what happens after the battery issue is addressed.

PS, it's also possible the new VS has a problem. We talked about this a long time ago; inside the VS can is a standard linear voltage regulator IC. The manufacturer of the IC specifies that it needs external capacitance for stable operation, but the VS being supplied back then did not have the capacitance. The result is a product that works sometimes, and sometimes not.

I bumped into the same problem when rolling my own VS; my first attempt would work fine on the bench (using my bench power supply for a 12v source) but then not work when installed in the car. Output would be way low for no apparent reason. Adding the specified capacitor fixed it.

Moss' VS supplier may well have fixed that problem by now; I simply don't know. But AFAIK Moss never publicly acknowledged there was a problem.
 
OP
K

karls59tr

Darth Vader
Country flag
Online
You might be able to fix the tr3 gauge, they are kinda interesting inside with these little coils that can be moved around. Perhaps the gauge has cased grounded there.

I had a friend who is really into electronics test the TR3 gauge and he determined that there was a dead short somewhere in the windings and that it would be a long painstaking process to try try and locate the break. Since I had a good TR4 gauge I went that route.
 
OP
K

karls59tr

Darth Vader
Country flag
Online
So, check the voltage coming out of the stabilizer, with the circuit complete (gauge and sender connected). If it is less than 10 volts, then the gauge will probably read higher when the battery voltage comes up (alternator is working).

I still don't think that is the problem (at least not all of it); but if the VS isn't supplying 10 volts, then you can wait and see what happens after the battery issue is addressed.

PS, it's also possible the new VS has a problem. We talked about this a long time ago; inside the VS can is a standard linear voltage regulator IC. The manufacturer of the IC specifies that it needs external capacitance for stable operation, but the VS being supplied back then did not have the capacitance. The result is a product that works sometimes, and sometimes not.

I bumped into the same problem when rolling my own VS; my first attempt would work fine on the bench (using my bench power supply for a 12v source) but then not work when installed in the car. Output would be way low for no apparent reason. Adding the specified capacitor fixed it.

Moss' VS supplier may well have fixed that problem by now; I simply don't know. But AFAIK Moss never publicly acknowledged there was a problem.

I'll check the voltage coming out of the stabilizer as you suggest and let you know.:encouragement:
 

Jim_Stevens

Jedi Trainee
Gold
Country flag
Offline
I'll check the voltage coming out of the stabilizer as you suggest and let you know.:encouragement:

I’m confused as to Why you are running a voltage stabilizer with an alternator? Didn’t you state that at the outset? They have built in voltage regulators, and typically, you gut or even remove the Lucas control unit. I know I did. The alternator and the VS may be working against each other.
 

TR3driver

Great Pumpkin - R.I.P
Offline
I’m confused as to Why you are running a voltage stabilizer with an alternator? Didn’t you state that at the outset? They have built in voltage regulators, and typically, you gut or even remove the Lucas control unit. I know I did. The alternator and the VS may be working against each other.
The later gauges (TR4 through at least TR6) work on a 10 volt supply, not battery voltage. The "voltage stabilizer" (a very poor name IMO) is what supplies the 10 volts.
 

Jim_Stevens

Jedi Trainee
Gold
Country flag
Offline
The later gauges (TR4 through at least TR6) work on a 10 volt supply, not battery voltage. The "voltage stabilizer" (a very poor name IMO) is what supplies the 10 volts.

Randall, you’re a god. Small “g”, but ​still a god!
 

TR3driver

Great Pumpkin - R.I.P
Offline
I put an early TR4 temp gauge in my TR3, so I've kind of been through this :smile:
It's interesting to note that Smiths made both types of gauges, but Triumph chose the ones that need the VS. I assume that means they were less expensive overall even with the VS.
 
Similar threads
Thread starter Title Forum Replies Date
K TR4/4A Voltage Stabalizer and Fuel Gauge Readings Triumph 5
Boink Early Mini Fuel Gauge - adjusting it British Motor Corp 0
S WANTED: Healey BN1 "Smiths" Fuel Gauge (Dead or Alive) Austin Healey Classifieds 3
R TR2/3/3A Fuel Gauge Triumph 19
T Wanted Smiths fuel gauge for Mk 1 Bugeye Sprite [FG2530/31] Spridgets Classified 1
S Fuel gauge calibration procedure Austin Healey 18
C MGA Fuel gauge question MG 7
S Wanted 1959 Bugeye Fuel Gauge Austin Healey Classifieds 0
K TR4/4A TR4 Fuel Gauge'"light bulb socket" type? Triumph 11
B For Sale MGA JAeger Fuel Gauge, Dual Safety Gauge, Speedometer and Tachometer MG Classifieds 0
B For Sale Austin Healey 100 Smiths Fuel Gauge, Dual Safety Gauge, Speedometer and Tachometer Austin Healey Classifieds 0
B For Sale Triumph Tr3 Fuel gauge Temp gauge Oil pressure gauge, speedometer tachometer Triumph Classifieds 0
K TR2/3/3A Re TR4 and TR3 fuel gauge sending units again.... Triumph 0
K TR2/3/3A Can a TR4A Fuel Gauge be swapped into a TR3A? Triumph 8
K TR2/3/3A Fuel Gauge again.... Triumph 11
N Fuel gauge problems? Spridgets 9
warwick-steve Fuel Gauge always shows 1/4 full Austin Healey 27
N Fuel gauge problem's? Spridgets 4
D Wanted TR3A Fuel gauge Triumph Classifieds 4
T TR2/3/3A Why is voltage stabilizer not needed for TR3 fuel gauge? Triumph 4
Tim Hollister Wanted Need Fuel Gauge for 1959 Bugeye Spridgets Classified 2
Lutz Kramer Fuel gauge and sender unit for BJ8 Austin Healey 2
George Zeck Looking for a fuel gauge ...... Spridgets 2
S Fuel Gauge Question Austin Healey 8
K For Sale TR3 Fuel Gauge Triumph Classifieds 8
warwick-steve Fuel Gauge always indicates 1/4 full. Austin Healey 13
J Fuel sender, fuel gauge 100 4 Austin Healey 6
George Zeck What fuel gauge SHOULD I have? Spridgets 3
sim 1958 fuel gauge sprite Spridgets 11
N Spitfire Fuel gauge Triumph 8
Martinld123 Austin Healey 100 BN2 fuel gauge not working Austin Healey 13
N Fuel gauge question?? Spridgets 3
B TR2/3/3A Fuel gauge problem Triumph 7
H TR2/3/3A Fuel sender or gauge? Triumph 8
F Running out of fuel - gauge problem? Austin Healey 5
K TR2/3/3A TR6 fuel gauge in a TR3? Triumph 1
K TR2/3/3A Fuel gauge and switching to Neg ground? Triumph 2
K TR2/3/3A Can a TR4A fuel gauge be used in a 3A? Triumph 8
toysrrus TR2/3/3A How to test fuel gauge & sending unit? Triumph 10
Rut Bugeye fuel gauge Spridgets 14
Editor_Reid Fuel Gauge for 1967 Sprite Spridgets 4
M TR4/4A Temperature and Fuel Gauge Wiring...Help Wanted Please Triumph 6
C TR6 Fuel gauge mystery Triumph 6
A Fuel Gauge - Help Needed Austin Healey 18
N Correct Bulb Holder for BT7 fuel gauge ? Austin Healey 4
T TR4/4A Fuel gauge Triumph 4
B TR2/3/3A Fuel gauge issue 60 TR3A Triumph 13
BlueMax Bugeye Fuel Gauge Spridgets 3
DanLewis Looking for an old-style fuel gauge [working or not] Spridgets 3
V Fuel Gauge Sending Unit Austin Healey 3

Similar threads

Top