TR7 Fuel Gauge & Sender

[redbulletv8]

I have a fuel gauge that does not work,I took the cluster out and found that the flexible track was damaged causing an open circuit.This has been replaced and on refitting cluster the gauge still did not work.I have changed it for one off a spare cluster I had and this one reads full when I know it is not.I used a potentiometer to find 1/2 full and that needed 1.25k.
I have took a reading from the sender and get 155 ohms,I have no idea of the range on the sender from empty to full so this reading does not mean much although it alters if I shake the car from side to side.
Does anyone know the sender range at all?
I have a feeling the gauge is faulty so it probably needs replacing anyway.
I have checked all the earths and cleaned them up and cleaned and tightened all connectors as the ones on the tank were a little loose and corroded.
Any feedback would be appreciated.

[saabfast]

When I got my car the gauge just read 'full' all the time. I changed the gauge (for a s/h one) and it has worked OK since. Not sure why but they seem to fail showing either empty or full.

[Beans]

Could also be that you have a punctured float, or the sender itself is at fault

[redbulletv8]

Perhaps if a resistance in ohms can be referenced to the 1/4, 1/2, and 3/4 full marks on a known good gauge and a resistance range of a known good sender can be found this could be placed on the help pages.
I will contact S&S after lock down and see if they have a gauge for sale.
Thank you for your replies.

[Hasbeen]

The first time I filled the tank on my 7, after building it from 2 wrecks, the fuel gauge read only 3/4 when the tank was filled up the filler neck. When checked I found the float had something like 15 to 20% of its capacity full of petrol.

Knowing that wood swells when wet with water, I drilled a small hole in the float to get the fuel out, then plugged the hole with a wooden plug carved from a Kebab stick, & tapped ti gently into the hole, trimming it almost flush, hoping that wood swelled in petrol in the way it did with water. The gauge still didn't read totally full, but is only half the needle width below full.

That was about1993, & the float was still empty when last inspected about 3 years ago, & the gauge still reads the same 27 years later. I think wood must swell in petrol.

Hasbeen

[Beans]

... That was about1993, & the float was still empty when last inspected about 3 years ago, & the gauge still reads the same 27 years later. I think wood must swell in petrol ...

The better "bodge"repairs

[saabfast]

Typical, got the 7 out on Sunday to clean for next weeks 'Classics for Carers' and my gauge went straight to 'Full'! Its been fine for years.

[redbulletv8]

I have fitted a replacement gauge from S&S and all is good.
Before fitting I made a note of the resistance between the 3 terminals and looking at the back of the gauge if you measure between the top terminal and the r/h lower one is around 545 ohms.
Between the top terminal and the l/h lower one is around 300 ohms.
Between the 2 lower terminals is around 245 ohms.
These readings I hope will save someone the hassle i've had.

[Beans]

Thx, good info!

[saabfast]

Thread resurrection but I have a recurrence of the problem of the fuel gauge reading full at all times. I cannot find a UKC511 gauge. Looking around I may be able to get an AEU1632 gauge but Rimmers site says this is for the very late push button instrument panel. Does anyone know if this will work with the earlier ('80) panel, or if it can be made to work?

[busheytrader]

I thought the difference amongst the late and early battery and fuel gauges was cosmetic. It’s years since I last looked at a push button dash assembly though.....

[saabfast]

Thanks, been told similar on the FB page so I think I will have to get the AEU1632 and change it.

[FI Spyder]

When I had my sender out (stripping and resealing gas tank) it had a little rust on it so I proceeded to clean it in some rust stripper. I got some on the coil (bad) and the ohms sweep wasn't smooth any more. Not having a replacement I put it back in as I was pressed for time to make the first car meet of the season. It worked fine and has been perfect for the last 10+ years. Sometimes it's better to be lucky than good.

[saabfast]

Bought the AEU1632 and changed it over today. The numbers on the backplate were exactly the same as the existing one (which I had changed about 10 years ago for one from a spare panel I had which was not push button either). The 'new' one now works. I had already added an extra earth connection from each end of the printed circuit the last time I had a problem.
I had tested the 'new' when it arrived and the resistance readings between the terminal were reasonably as the figures which had been given. Tested the 'old' one taken out today and it seems to be open circuit on two of the three readings which explains why it did not work. No idea how that happens on a unit protected in a dashboard and hardly used though.
There is a dodgy connection somewhere though. The dash backlighting seems to be intermittent dependent on the multi-connector. The connector is on OK but it needs a bit of pushing around by grope to get the lights on, maybe a fault in the printed circuit.

[CamGTS]

don't you/we love BL electrics???