Fuel gauge problem

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53lake
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Fuel gauge problem

Post by 53lake »

On my 1968 Traveller, looks like I've created a problem I need some advice to fix.

Ever since I've owned the car, the heater motor hasn't worked. I've done a full restoration on the car in the last 4 years, and part of that was cleaning up the heater matrix and checking the motor, which worked OK out of the car off a battery. I found the feed wire was dangling loose behind the fascia, so that was the problem (!).

On replacing the motor, I consulted the wiring diagram to see where the feed to the motor should be connected, and after some head scratching, decided to add it to the feed side of the voltage stabiliser, where there was a spare terminal. Blower then worked fine.
However, with the speedo out and propped up in the aperture while I checked the blower, I saw a slight wisp of smoke, and quickly shut off the ignition. I guess I earthed a terminal by mistake. One of the fuses had blown, so I replaced that, and more carefully put the speedo back.
However, now the fuel gauge doesn't work properly. I've disconnected the feed wire to the sender unit and earthed it, but the gauge then only creeps up to about 1/8, and wavers slightly at that point. I understand it should read full if the sender is bypassed. The sender unit is new by the way. I'm assuming I've messed up either the fuel gauge or the stabiliser unit. Can anyone help with figuring this out? Thanks!
irmscher
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Re: Fuel gauge problem

Post by irmscher »

Most probably burnt the stabiliser out :(
Sleeper
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Re: Fuel gauge problem

Post by Sleeper »

" with the speedo out and propped up in the aperture while I checked the blower, I saw a slight wisp of smoke "

IMHO you've smoked the fuel gauge , the case should be properly earthed for it to function correctly , and I may be corrected here , and hope I am , but If you apply 12Volts and the guage without it being properly earthed , it's toast.

John ;-)
Last edited by Sleeper on Fri Apr 30, 2021 4:03 pm, edited 1 time in total.
53lake
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Re: Fuel gauge problem

Post by 53lake »

OK, thanks for the replies. So what would be the procedure to check whether it's the stabiliser or the gauge needs replacing (or both!).
Simple please, obviously I'm not very competent in electrics...
Thanks
Sleeper
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Re: Fuel gauge problem

Post by Sleeper »

Stabiliser....multi meter set on DC Volts , check input 12 to 13 volts , check output 10 volts with ref. to earth.

Gauge ??

John :-)

P.S. Just edited my earlier , should ( and now does ) read GUAGE ( not sender ).
53lake
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Re: Fuel gauge problem -again. Any ideas?

Post by 53lake »

Continuing the issue I ran into last year.

After all the above, I replaced the voltage stabiliser with a solid state one (-ve ground) from ESM. Gauge then worked fine, all good. That's been the case since June last year.

Just recently when driving to the local garage for the annual inspection, I noticed the fuel gauge again not working (with the tank at least 3/4 full). Luckily, they didn't notice the gauge, and it passed.

This is a 1968 Traveller with black face speedo.

So this is where I'm at:

- Disconnected the feed wire to the sender unit, and grounded it, no response from the gauge.
- Speedo out. Checking the stabiliser, multimeter across B terminal to chassis shows 12.4V. Perfect.
- Multimeter across I terminal to chassis shows 9.94V. Again, what it should be.
- Removed the fuel gauge from the speedo, and connected the in and out wires together, thus eliminating the gauge from the circuit.
- Multimeter from end of sender wire to chassis shows 9.94V, ie no break in the circuit all the way to the sender, and the right voltage being delivered.
- Connected the fuel gauge from end of sender wire to chassis. No response from gauge.
So at this point I'm thinking the gauge is bad.

I find a regular 9V battery in the house, connect it across the fuel gauge, it drifts up to full just fine.
So what's going on here? Seems the gauge responds to 9V from a simple battery, but won't respond to the 9.94V chopped from the stabiliser.

I tried again with an additional ground wire from the gauge casing to the chassis, but it made no difference, still the gauge refuses to budge.
Any ideas welcome!
don58van
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Re: Fuel gauge problem

Post by don58van »

What a frustrating problem. You say that you have put a 9v battery across the gauge but have you tried the output of the voltage regulator and earth direct across the gauge (no other circuitry involved)? Sometimes a power source will deliver the required voltage but negligible current. That is stabilizer (actually an electronic regulator in your case) may be faulty even though it appears to be delivering the required voltage.

BTW
9.94V chopped from the stabiliser
Unlike the electro-mechanical stabilizer you replaced, the voltage is not chopped in the case of an electronic regulator--it is a steady voltage.

Don
53lake
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Re: Fuel gauge problem

Post by 53lake »

Thanks Don,
I connected the fuel gauge between the regulator I terminal and earth, still no response from the gauge. Checked the voltage across the gauge terminals, less than 1 volt. I'm no electrician, but should it not be the same 9.94V the regulator is sending? Perhaps this is telling me the gauge is bad, maybe it was damaged originally in the short I created last year (see earlier post).

It occurred to me that having the speedometer out of its housing and supported with a bungee cord to stop any terminal from shorting out like before, that the speedometer housing isn't earthed, therefore neither is the regulator housing. So I put a jump wire from the speedo casing to earth and tried everything again. Still no response.

Finally, confirmed again that the gauge responds OK when connected across a 9V battery.

Other than what I've already done, I'm not sure how to diagnose if the gauge is really duff, or should I replace the stabiliser/regulator again?
Thanks for any other ideas.
don58van
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Re: Fuel gauge problem

Post by don58van »

It is telling that the gauge still responds as expected when connected to a 9v battery. That tells me that the windings in the gauge are intact.
This tends to confirm my suspicion that the regulator may be damaged in that it is incapable of delivering its current/voltage when under load.
Just to be sure the gauge is OK, I will test the resistance across a spare gauge today to give you a figure to look for on yours.
Don
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Re: Fuel gauge problem

Post by don58van »

I just checked a spare (black) fuel gauge (no connections)--about 60 ohms.
Don
53lake
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Re: Fuel gauge problem

Post by 53lake »

Thanks - I got 62-63 ohms when it had settled down, but it did jump around a lot as I applied gentle pressure with the probes on the gauge terminals.

So good, but I'm wondering if there's a loose connection somewhere in the gauge which might also be the source of the problem (and I did use pressure on the terminals to connect it to the 9V battery each time). I gently loosened the brass ferrules on each terminal and tightened them back up, but that made no difference and beyond that the gauge looks too delicate to go pulling it apart (not even sure how to get it open and what to look for anyway!).

Since a new regulator is easier to obtain than a gauge, I'll get one from Moss in California, should be about 7-10 days delivery, then I'll report back.
Thanks so much for your help!
don58van
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Re: Fuel gauge problem

Post by don58van »

simmitc
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Re: Fuel gauge problem

Post by simmitc »

You could get a 9v lamp (bulb) and try running that from the regulator as that would but a load on it. Only a very low wattage, not sure what amperage is available from the regulator, but if the lamp does not light then it confirms that the regulator is not working under load.
don58van
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Re: Fuel gauge problem

Post by don58van »

You could get a 9v lamp (bulb) and try running that from the regulator
A 12v dash lamp would probably do. But don't leave it illuminated (if it does) for more than a few seconds to limit stress on the regulator. It would be good to have your voltmeter wired in when doing the test to see if the volts dive down when the load is applied.
Don
53lake
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Re: Fuel gauge problem

Post by 53lake »

Thanks - I'll try that, but I already ordered the new regulator from Moss (it's returnable if needed). I will be visiting relatives in the UK in October, so in case I need a replacement gauge, I'll know by then, can order one on eBayUK, and have it sent to my relative. So that's the plan right now.
Again, many thanks for the suggestions!
don58van
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Re: Fuel gauge problem

Post by don58van »

I will be visiting relatives in the UK
53lake
Are you not in the UK? I am in Australia.
Don
53lake
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Re: Fuel gauge problem

Post by 53lake »

I'm in Texas :D
53lake
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Re: Fuel gauge problem

Post by 53lake »

Pleased to say that the new voltage stabiliser/regulator from Moss is installed, and now I have a working fuel gauge.

Evidently the solid state stabiliser (part No. 131-555) that I had bought last year from Moss (not ESM - my bad) had quit working. The one I replaced it with (Moss part No. 115-433) seems to work. This one isn't described as solid state, and had a different mounting plate attached so I had to rig a new plate to get it to fit to the speedo with the "Top" label up.

Think I'll have a word with Moss and see if they have any comment on the situation.

Thanks for the helpful advice!
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