O

Old Seadog

Member

• Nov 23, 2018

• #1

1984 ex-army 109 canvas top. The fuel gauge reads full on both tanks as soon as the ignition is turned on. I was advised to get new fuel tank sender units but that made no difference. So I had the senders checked and they work okay according to the electrical resistance thingy they tested them with.
Then someone said it might be the voltage regulator but since the temperature gauge works and it apparently uses the same regulator, it can't be that.
Another pundit said to check the earth on the instrument panel but that must be okay because both the temperature gauge and the instrument lights work.
Another suggestion was that perhaps the gauge itself was faulty but I'm doubtful about that, too, when it reads empty with the ignition off and rises slowly to full as soon as I switch on. Or is there more to it than that?
Any suggestions will be very welcome. Thanks in advance.

 

Shippers

Well-Known Member

• Nov 23, 2018

• #2

On my 101 last week fuel gauge reading empty when ignition on...checked everything and it was v.reg so by passed it and it now reads ok...an earth fault will show a full tank on ign on...if you take supply of the sender with ign on does the gauge drop?...

 

jamesmartin

Well-Known Member

• Nov 23, 2018

• #3

if live wire from gauge to sender gets earthed before the sender, gauges will read full, switch over valve is a common place

 

R

rob1miles

Well-Known Member

• Nov 23, 2018

• #4

Agreed, short to earth will read full. Could be rubbing on an edge where it passes under the bulkhead.

 

O

Old Seadog

Member

• Nov 24, 2018

• #5

Shippers said:

On my 101 last week fuel gauge reading empty when ignition on...checked everything and it was v.reg so by passed it and it now reads ok...an earth fault will show a full tank on ign on...if you take supply of the sender with ign on does the gauge drop?...

Click to expand...

It does.

 

Shippers

Well-Known Member

• Nov 24, 2018

• #6

Then as James said probably earthing out between gauge and sender...

 

O

Old Seadog

Member

• Nov 24, 2018

• #7

jamesmartin said:

if live wire from gauge to sender gets earthed before the sender, gauges will read full, switch over valve is a common place

Click to expand...

Same on both tanks so the changeover switch has got to be on the list. Thanks.

 

O

Old Seadog

Member

• Nov 24, 2018

• #8

Shippers said:

Then as James said probably earthing out between gauge and sender...

Click to expand...

It's the same on both tanks, so at least we know where to start looking - where the two join, presumably.

 

Shippers

Well-Known Member

• Nov 24, 2018

• #9

Can be a pain to trace sometimes but at least you know the problem...good luck...