72 baywindow fuel guage woes

[plimthing]

Hi, ive been reading for a few days now the previous posts regarding testing the gauging system on various types of gauging models.
However mine is being a bit weird. The guage since ive had the van hasn't moved no matter how much fuel ive had in it for engine testing etc ( bare in mind this bus hasn't moved under its own steam more than 100 metres since ive owned it) which totals around 20 litres or so ( mmm whats that er 4-5 gallons?!).
The vibrator thingy with power supplied gives a nice voltage pulse as I'm led to believe it should. The guage mechanicals seam to move ok and needle isn't obstructed. The sender is an unknown quantity...so some advice on testing this would be good. Its the type that's bolted down with one connection for the Brown/white wire and a ring terminal for a ground under one of the unit securing bolt heads.
I have continuity from the sender wire at sender unit end right through to where it connects to guage on dashboard. I have power from no11 fuse when key is turned 1 click. All connections have been cleaned and wire brushed.
So when I grounded the brown/white wire at sender end the guage fired into life to nearly full and then slowly died off and is hiding out of sight. No matter what I do now, the guage does not move at all not even a shiver.
Any ideas? As far as I can see there is only a guage, vibrator, sendor and a wire in the system. Do gauges die or is it more likely the vibrator/sendor?
Thanks in advance
Tony

[busdaddy]

A 72 doesn't use the vibrator, are you sure the gauge or instrument cluster hasn't been swapped for something newer?
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[Tram]

Tony- Ground your gauge wire somewhere on the body and see if your dash gauge pegs on full and stays there. If so, the gauge is OK.

If your Bus has been laid up very long prior to your ownership my bet is on the tank sender.
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[plimthing]

I'm unsure of anything in this bus! Its been a nightmare from day one
I think its a vibrator anyway, its a rectangular box under the gauge with a '+' terminal and one other which has a small wire connecting it to the gauge. The gauge's other connection receives the brown wire from sender unit.
Which wire do you want me to ground out? the one on the gauge unit opposite the sender one???
But surely if it was the sender that was bad, when I removed gauge wire from sender and grounded that, the gauge would always go to full deflection? Where as mine did it once then died.

[Tcash]

[busdaddy]

How about a photo of your gauge?, the bolt down sender system doesn't use a vibrator but the later gauge system does (as well as a different sender).
Right now it sounds like the gauge crapped out, or more likely that vibrator which regulates the power supply to the system. A pic of your gauge will tell us if you can delete it.
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[plimthing]

ok give me 10mins and I will try and get you some pics of everything...
Thanks everyone

[plimthing]

ok these pics show the sender with appauling access hole hack by PO, drivers view of gauge, and a couple of pics of wiring.
Hope you can see everything to let you know what I'm dealing with!

[Xevin]

Pretty sure that’s a compatibly issue. Late bay fuel gage. With 72 fuel sender. Better explanation coming I’m sure.
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[busdaddy]

Yes that is a late gauge, it can work with an early sender so let's find out what's bugging it.

Since you already tried grounding the wire at the sender and got a momentary full reading we can be reasonably sure the wire between the front and back is somewhat intact. Now you need to test for voltage at both the black wire and the red wire on that vibrator (key on, brown/white wire grounded at the tank). You might also try a ground jumper to the terminal with the brown wire on it to rule out wiring to the rear.

Your sender will still need the repair Tcash linked, but unless you get the gauge working too it won't matter.
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[plimthing]

Thanks for all help.
I will have to do these checks in morning, I will report back findings then.

[SGKent]

I am reading this slightly different than a couple other folks.

If grounding this wire makes the gauge go up towards full then everything from that wire forward works - although it may not be as accurate as you like.

But if grounding this wire MADE the gauge work THEN it went back below empty while grounded, or is stuck somewhere else once the wire is back OFF then the gauge did work but probably burned up. These gauges are not made well enough to sit on fully grounded for too long without being damaged.

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[Tcash]

Maybe the brown wire from the tank to the gauge is bad.
To rule it out, bypass it and jump the brown wire at the gauge.

Good luck
Tcash

[skills@eurocarsplus]

why not ditch the late (incorrect) fuel gauge and stop the madness now?

get the correct gauge in there and kick the previous owner bullshit out of that poor thing.

yes, it CAN be made to work, but get the vibrator dingus out of there and get the correct gauge in there.
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[TomWesty]

If it were mine, I would take the combination of what SGKent said and what Skills said and run with that.
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[plimthing]

ok, thanks for answers! I'm happy to ditch all and go for original early bay parts, I'm just trying to locate them in UK. Will the early gauge just slip right in to where the late on sits or do I need to buy a new instrument cluster for it??
I'm interesting to figure out if I can get this set up working though!
I'm of the thinking that the gauge burned out after being grounded out. I will pull it out again and see what I can see.
I will also check what voltages are there when I turn the key.
I will report back later!

[plimthing]

ok done a couple of tests ..
With Key on, voltage in to stabilizer = greater than 10 volts ( battery voltage)
---""------- voltage out of stabilizer = 13.5volts
With engine running.. input 12v output 13.5v
Grounding the gauge ( instead of brown/white sender wire) = no movement of gauge at all
There is quite high resistance between the two terminal posts on the gauge, high enough not to get a continuity beep from my meter.
I have not tested the sender yet, but I'm trying to decide whether to replace the bad parts in this late set up or go back to early bay set up.
I don't mind buying new parts, I do like getting old things to work...
Will report back on the sender.

[plimthing]

so ive been looking into new parts, and I can get an early bay gauge and sender for £100 ($140 maybe) but the gauge wont fit into my late bay cluster! I cannot buy a late bay Gauge from any of the usual suppliers in UK. I can get a 2nd hand Instrument panel from a late bay with a fuel gauge in it, but of course theres a chance the gauge is going to be stuffed in that too... but for £10 (at the moment) might be worth a shout.

[Tcash]

You may want to repair your old Sender. There have been many reports of the new aftermarket senders not working properly.
Good luck
Tcash

Another fuel sender repair method T2a
Fuel Gauge Vibrator got ya down? FAQ

[plimthing]

Thanks Tcash, I will take it out later, I'm at work tonight so hopefully one of the more gifted Avionics chaps will do a spot of soldering for me! I am currently one handed as I managed to put a 1/8" drill through my thumb ( after the drill had snapped)and damage nerves etc.... didn't hurt going in but putting drill in reverse to get it out... now that's a pain that makes your eyes water!