Fuel Gauge - how to test

[Ben]

Ok so I've been working on a '65 Pagoda for a while now and I am baffled by the non-working fuel gauge. I removed the early style sender and checked it and it looks fine, worn, but fine. I have continuity between Earth and G, and the resistance changes as I move the float. I have continuity between Earth and WC, which is the warning light too, however no light on the dash.

I have power on the wire up to the dash gauge too, however if I earth either wire at the sender, blue/black or blue/green, I get no response from either the gauge OR the light.

Curiously if I connect power to the blue/black at the tank connection ( which I found out inadvertently using a test lamp) the gauge reads full !

Where am I going wrong ?

I am about to pull the gauges out but I would rather do that as a last resort. Does anyone know a secret dance I could perform whereby everything works magically again

[w113dude]

Isn't there another wire connector between the dash wire and the sender unit? I don't know much about the early models but I think there is one in the trunk if there is, check those pins for corrosion. It's the only thing I can think of.

[Ben]

Hi Shaun,thanks for replying.The wiring diagram shows a connection, item # 46 "Plug connection Tail Light Leads" but I think this is the one located in the front left kick panel. I must admit I did not look there as this car is RHD and there is a lot of non factory wiring there which I wanted to stay away from. However I think I will rule that out before attempting to remove that centre cluster.

I'm still unsure about why applying 12+ makes that gauge move and grounding does nothing. I managed to obtain an early sender Unit just now that appears in perfect order, so fingers crossed I get it sorted.

[JamesL]

Hey Ben

Nothing to add but long time no see! How are ya?

[Ben]

Very well thank you and hope you are too. Busy with these lovely old cars but still lurk here quite a bit. Thanks for the recent recommendations BTW

[ja17]

Hello Ben,

What is the history of the gauge?  Did it ever work?  There are early and late gauges and senders. They are not inter-changable.  I normally test by removing the sender and moving it up and down to observe the gauge. Make sure the ignition is on.

The change in early and late type happened at #.....008954.  Resistance at full tank in the early sender was 59.4 ohms full and 118.4 ohms empty.


On the late version resistance of the  sender was 4.5 ohms full and 65.5 ohms empty.

*information taken from my notes, I believe them to be correct.

[Ben]

Hi Joe, hope you are well ! The car has been apart and restored. Everything went back in over the last few weeks and the gauge worked initially. Then the dash lights failed so I took the clicks out again and sorted that. The gauged worked then too but I noticed a day it so ago it read empty. I assumed a connection problem and went about checking. The sender is definitely not working BUT I was confused by the reactions I got when earthing the connections at the tank and then wondered if the dash gauge was also faulty I have a working early sender now ( already tried a later one) but haven't tried it yet. I will do so now and report back.

[Ben]

Just to finish this both sender and gauge were faulty. With the new sender in place a few taps in the glass and the gauge sprung to life. It sticks every now and then so some internal fault I suppose.

[ja17]

Nice job Ben,

Having two issues really complicates the diagnostic process! 

Happy Motoring!
Joe Alexander
Blacklick, Ohio

[Brian Davidson]

Ben. any irish pagoda plans for next year. Brian.

[Ben]

Hi Joe, yes I was unlucky AND lucky at the same time, having the spare Units. It just puzzled me and i couldn't make sense of it.

Hi Brian, I think the Club have some plans since its the 50th anniversary of the W113. We will be making these cars the showpiece on the trips and shows we organise. Maybe we will see you ??