On 30 May, Randall <TR3driver@ca.rr.com> wrote:
>>
>> - 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?
>
>You've got multiple bad connections, in the sense they present some
resistance. Not at all unusual on these old cars.
>
>The variation is most likely the sender jumping around, but could also be
an intermittent connection somewhere.
>
>I would start walking along the circuit, going point to point along the
conductor instead of each point to ground. Maybe start with the battery
hot post to the terminal for the brown wire at the starter solenoid. Then
that terminal to A1 on the fuse block >(which should be a direct run of
fairly heavy brown wire). Etc, etc. Each time you find a voltage drop,
disassemble, clean and inspect the joint.
>
>If the drop is happening in the wire, consider replacing the wire.
>
>But my guess is that you have a post-60K TR3A with the Lucar connectors,
and you'll find that all the drops are happening at the Lucar connectors.
They were never designed to last this long! Generally though, cleaning
the male tab, smearing a little bit of >your favorite preservative on it
(silicone grease or even Vaseline), and pinching the female connection a
bit before reinstalling it; will make a noticeable improvement. If not,
the next step is to replace the female connector. Preferably (IMO) with a
quality >non-insulated terminal, both crimped and soldered to the wire,
then insulated with two pieces of heat shrink tubing. I put a short slide
show up at https://imgur.com/a/yETAubD
>
>-- Randall
Thank-you for your reply.
You are correct in that my car is post 60000 and has Lucar connectors.
I've changed a couple of the connectors in chasing down the fuel gauge
issue. I also changed the fuse box. The wire did look like the first image
in your slide show.
I'm not clear on what you mean about "going point to point along the
conductor instead of each point to ground". I can do a continuity check or
test for resistance between two points on a wire, but I can only measure
voltage at a point to ground. Sorry if I'm a bit dense in comprehending
your meaning.
Is there a point at which the voltage is too low for the fuel gauge
circuit to work? I'm more familiar with digital circuitry where there is a
clearly defined range for 1 and for 0. As long as one is inside the range
all is well.
Thanks,
Dave MacKay
TR3A s/n 68639L
Near Toronto, Canada
** triumphs@autox.team.net **
Archive: http://www.team.net/pipermail/triumphs http://www.team.net/archive
|