[TR] Troubleshooting TR3A fuel gauge

[Wbeech@flash.net]

Barney at Mgaguru.com is a good guy that knows his stuff.   Ohms should roughly go from 10-90(Barney says 0-70) with the clothes hanger and all wires disconnected.  

Check all your related connections, the sender and the gauge need to be grounded.  

I would expect 12v at the hot post of the gauge.  If your not getting it try a direct jumper and test the system.   New gauges are NLA but you can either find them on eBay or other parts sites, or send your gauge AND sender to one of the several reputable instrument rebuilders. 

Bill B
TS30800L

Sent from my DynaTAC 8000X

On May 29, 2019, at 10:29 PM, Dave MacKay <dave at mdmackay.ca> wrote:

Hello:

I’ve been troubleshooting the fuel gauge on my TR3A because it has not been providing an accurate indication (or even a reasonable approximation) of the fuel level in my tank.

I referred to a number of documents and old posts about how to troubleshoot and calibrate the fuel gauge and sending unit (e.g., https://www.triumphexp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-tr-3.1244960/ and http://mgaguru.com/mgtech/electric/fg_01.htm).

I started by looping a clothes hanger around the float in the tank and reading how many ohms I saw at different levels. What I found was that the reading fluctuated --- it didn’t stay the same even when I held the float at one level. I then checked to ensure that the grounds were good (they were). Before concluding that the sending unit was flakey, I thought I’d better ensure that I was getting good power to the unit.

That’s where things got weird.

-       I read 7.6V between the sending unit and ground.

-       I read 7.65V between the T terminal of the fuel gauge (which connects to the fuel tank sending unit) and ground. However, this reading was erratic; the value would change to, say 4V.

-       I read 10.6V at the B terminal of the fuel gauge

-       I read 10.9V at the A4 terminal of the fuse box.

-       I read 11.9V at the A2 terminal of the fuse box.

-       I read 12.5v between the terminals of the battery.

I’m a bit baffled. I expected that I’d see about 12V at all points. Even if the fuel gauge was bad, I would have expected to see the same voltage at the battery, A2, A4, and the B terminal of the gauge. As it is, I’m seeing a drop of about 2V among them.

What might be causing the voltage drops that I’m seeing? Could it be as simple as a broken fuel gauge? If so, how could I test that?

Moss lists the fuel gauge as NLA. Does anyone know of another source?

BTW, when I switched my generator for an alternator years ago, I eliminated the control box (regulator). 

Thanks in advance.

Dave MacKay

TR3A s/n 68639L

near Toronto, Canada


** triumphs at autox.team.net **

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/pipermail/triumphs http://www.team.net/archive

Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/wbeech@flash.net
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/triumphs/attachments/20190529/abcc3aec/attachment.html>