7 replies to this topic

[Spaceframe7]

Hi all. This question is perhaps more appropriate for the vintage car enthusiasts, but has anyone overcome the problem of using a fuel sender from one manufacturer (Smiths/Caerbont) with a fuel gauge manufactured decades ago (in the U.K.) by AC Delco? A friend in the U.K. has tried to use the two together, but says that the AC gauge reads in the opposite direction to the sender, but reversing wires does not overcome the problem and the two just won't work. He compared the fuel gauge to a voltmeter, but said he tried every way to overcome the problem without success. Is it something to do with the resistance of the Smiths fuel sender possibly? Apparently top-mount AC Delco fuel tank senders are rare or non-existent. Seeing as this should be basic direct current theory I am puzzled why they are not compatible, but without my clumsy attempts at trying it and possibly wrecking one or both, I am rather reluctant to experiment. I could always use a Smiths fuel gauge of course, but these are not authentic for my re-build. I have been advised by a U.K. auto electric company that AC and Ford work similar to one another and that possibly Smiths and Jaeger senders/gauges are compatible, but apart from that, they were unable to assist. Any suggestions or ideas please?

[Ian G]

Long time ago(1970) but we had a similar problem when we fitted a second tank to our Rally car,stating the obvious i know but the fix was(IIRC) to fit the sender unit upside down.

[Canuck]

If the resistive element's action is opposite to what you need (resistance goes up with decreased fuel level but gauge level goes up, or vice versa) then there's three options - install upside down as per the above, remove the resistive element as re-mount it 180' in it's housing or build an out-board translator circuit.

[McGuire]

Hi all. This question is perhaps more appropriate for the vintage car enthusiasts, but has anyone overcome the problem of using a fuel sender from one manufacturer (Smiths/Caerbont) with a fuel gauge manufactured decades ago (in the U.K.) by AC Delco? A friend in the U.K. has tried to use the two together, but says that the AC gauge reads in the opposite direction to the sender, but reversing wires does not overcome the problem and the two just won't work. He compared the fuel gauge to a voltmeter, but said he tried every way to overcome the problem without success. Is it something to do with the resistance of the Smiths fuel sender possibly? Apparently top-mount AC Delco fuel tank senders are rare or non-existent. Seeing as this should be basic direct current theory I am puzzled why they are not compatible, but without my clumsy attempts at trying it and possibly wrecking one or both, I am rather reluctant to experiment. I could always use a Smiths fuel gauge of course, but these are not authentic for my re-build. I have been advised by a U.K. auto electric company that AC and Ford work similar to one another and that possibly Smiths and Jaeger senders/gauges are compatible, but apart from that, they were unable to assist. Any suggestions or ideas please?

There isn't enough info here to sort it out. Your meter (tank unit) and gauge (dash unit) may be compatible, compatible with modifications, or incompatible. With components from two different vehicles or sources (?) like this it's basically dumb luck to arrive at full compatibility as there are many types of setups. The meter may register from say, 10 ohms at full to 90 ohms at empty, or vice versa. Or 20-150 ohms, 40-270 ohms, etc, ad infinitum. There are nearly innumerable calibrations and the meter and gauge must be matched to attain any accuracy, naturally. Also, there are voltage-stabilized gauges that operate at voltages other than 6V or 12V through a stabilizer or constant voltage regulator. Both Smiths and AC supplied across the industry so based on the limited info here, you could have most anything. You may even have a magnetic gauge unit though it's unlikely. You say decades old but that's not very old anymore. Heck, that's the '80s; how time flies.

Also, it is not terribly reasonable to simply assume that both your components are functioning normally to begin with. I would start here: remove your tank unit, attach an ohmmeter across the terminals, and record the resistance while sweeping the float arm from empty to full (making sure you note which is which) while also watching for dropouts through the range. Next, you can do a basic test of the dash unit by supplying power and ground. With the wire to the sender open, the gauge should go fully full or totally empty, and with the wire grounded it should go opposite. From there you can sort it out. One easy way to proceed: take the gauge and the meter specs you recorded to an instrument shop and tell them to calibrate the gauge to the meter. If it's possible in your case and they know their stuff, they'll know just how to do it -- though it may be more expensive than simply buying new, compatible components. If you want to take it further on your own I will need more info.

[Tony Matthews]

Is it possible to re-build a Smiths unit to look like an AC Delco? Swop faces, needles and bezels - I assume you can match sizes. Or perhaps you will only be happy with the original-spec part...

[Spaceframe7]

Is it possible to re-build a Smiths unit to look like an AC Delco? Swop faces, needles and bezels - I assume you can match sizes. Or perhaps you will only be happy with the original-spec part...

All above advice much appreciated. McGuire, thank you for your input. I wasn't sure where to start, but will follow your directions, and obtain all the necessary specs. The gauge and set-up I have are from approx. 1968 onwards period of production.

Tony, thanks for the thought. I purchased a genuine vintage Smiths fuel gauge from a car wreckers yard, and took it apart. I tried to fudge the internals and see if the AC facia etc. would fit but no luck. I also tried a company in the U.K. for some 'lookalike' gauges, but they can only provide versions of the Smiths gauge with 'AC' printed on the different facia, but otherwise Smiths appearance (there are subtle differences - I know I'm being overly fussy, but I would rather have the 'belt and braces' 'AC' version - much better constructed and authentic). The new-build Smiths gauges are now very expensive, (£80.00 plus for a modified gauge), made mostly of plastic apparently (all the non electrical parts are plastic - including the case) and to my mind - not really worth it. I know someone who purchased a pair that had been re-lettered and for what he paid - I don't think that I will consider this option. I have been successful in obtaining the correct AC gauges on e-bay for very good (low) prices, but the AC sender seems to be very elusive to find (I'm searching from abroad - no access to autojumbles unfortunately!). Thanks all. SS.

[Tony Matthews]

Tony, thanks for the thought. I purchased a genuine vintage Smiths fuel gauge from a car wreckers yard, and took it apart. I tried to fudge the internals and see if the AC facia etc. would fit but no luck. I also tried a company in the U.K. for some 'lookalike' gauges, but they can only provide versions of the Smiths gauge with 'AC' printed on the different facia, but otherwise Smiths appearance (there are subtle differences - I know I'm being overly fussy, but I would rather have the 'belt and braces' 'AC' version - much better constructed and authentic). The new-build Smiths gauges are now very expensive, (£80.00 plus for a modified gauge), made mostly of plastic apparently (all the non electrical parts are plastic - including the case) and to my mind - not really worth it. I know someone who purchased a pair that had been re-lettered and for what he paid - I don't think that I will consider this option. I have been successful in obtaining the correct AC gauges on e-bay for very good (low) prices, but the AC sender seems to be very elusive to find (I'm searching from abroad - no access to autojumbles unfortunately!). Thanks all. SS.

I quite understand you wanting authentic parts - I would too! You haven't said what the vehicle is, but there must be a club or association of other enthusiasts. My philosophy is always ask, you never know what the answer will be!

[Lee Nicolle]

What Mac says is very commonsense. Personally I would just find a good instrument repairer [though coming harder to find] and get them to do the job. Even after that never expect absolutely true readings as for mine any fuel guage of that era whatever brand is an indication there may be some fuel in the tank!!