by VanninBlaino Mon Feb 13, 2012 6:09 pmAnyone have problems with gas gauges in their A100s? My doesn't work, we tested the fuel sending unit, and it wasnt the problem, but we changed it anyway. I'm thinking it could be the wiring, but we pulled the gauges apart and they don't look to hot either. Anyone have parts/spare clusters?
5 posters
Common gauge problems?
VanninBlaino- Number of posts : 361
Location : New Orleans, LA
Age : 29
Registration date : 2011-05-30
RodStRace- Number of posts : 3046
Location : Chino Valley
Registration date : 2010-01-21
The gauge gets power thru a voltage regulator that supplies 5 volts. It's on the back of the cluster.
The voltage goes thru the gauge then out on a wire to the sending unit.
The sending unit is a variable resistor. It decreases the voltage even more.
Then the voltage travels to ground thru the body of the sending unit and a special ground strap that staddles the rubber line at the unit. The line is held in place with straps and grommets.
First quick check is to turn ignition on. This supplies voltage all the way back to the sending unit if all is right. Check voltage back there.
If it's 5 volts, the problem is downstream, meaning the sending unit or the ground connection. Note that many people have said that the replacement sending units are not calibrated properly.
Connect a good ground wire to the sending unit and recheck. If it works, the ground is bad. If it still doesn't work, remove the sending unit or grab the old one.
Connect the gauge wire to the unit and a good ground wire to the body or the unit. Move the float up and down while having an assistant watch the gauge. This will test the sending unit. It responds slowly so it doesn't 'bounce' driving down the road.
If there is not 5 volts at the gauge wire back by the sending unit, you need to check that wire at the gauge.
If there is power there, follow the wiring between the sending unit and the gauge.
If there is no power at the gauge output wire, check for voltage at the input wire. It should be 5 volts. If there is power there but not the output, it's the gauge. If there is no power at the gauge input, it's probably the regulator.
The voltage goes thru the gauge then out on a wire to the sending unit.
The sending unit is a variable resistor. It decreases the voltage even more.
Then the voltage travels to ground thru the body of the sending unit and a special ground strap that staddles the rubber line at the unit. The line is held in place with straps and grommets.
First quick check is to turn ignition on. This supplies voltage all the way back to the sending unit if all is right. Check voltage back there.
If it's 5 volts, the problem is downstream, meaning the sending unit or the ground connection. Note that many people have said that the replacement sending units are not calibrated properly.
Connect a good ground wire to the sending unit and recheck. If it works, the ground is bad. If it still doesn't work, remove the sending unit or grab the old one.
Connect the gauge wire to the unit and a good ground wire to the body or the unit. Move the float up and down while having an assistant watch the gauge. This will test the sending unit. It responds slowly so it doesn't 'bounce' driving down the road.
If there is not 5 volts at the gauge wire back by the sending unit, you need to check that wire at the gauge.
If there is power there, follow the wiring between the sending unit and the gauge.
If there is no power at the gauge output wire, check for voltage at the input wire. It should be 5 volts. If there is power there but not the output, it's the gauge. If there is no power at the gauge input, it's probably the regulator.
jkr- Number of posts : 1148
Location : prince edward island canada
Age : 66
Registration date : 2008-05-29
and a friendly reminder to all, the wire from the temp sender is a "resistance" wire. that means there is installed resistance in it from the factory. should anyone replace the harness across the engine be prepared for a hyper active temp gauge if you did not save the first 2 feet or so. just sayin cause i did it and had to get a salvage piece to correct my stupidity..........
slowflapper- Number of posts : 956
Location : GA
Age : 54
Registration date : 2010-07-29
here's some copy/pasta from a similar thread:
Here is some details on the problem: link
Depending on the year you may have an external "gauge voltage limiter" screwed to the back of your instrument cluster or it may be an internal unit that is inside the fuel gauge. My '65 has the unit inside the fuel gauge, 12v goes into the fuel gauge and then a 5v jumper wire goes over to feed the temp gauge.
Taking a reading off of your sending unit wire, a full tank will read 9 to 10 ohms, an empty tank will read 96 to 98 ohms, 1/2 tank will be 60'ish ohms. You should have a fluctuating 2-5v coming out of your gauge voltage limiter, if you put a solid 12v on those gauges you'll let the magic smoke out.
If the internal limiter is bad you can send the gauge off and have it bypassed and use an external limiter. If you have an external and its bad just replace it:
NAPA has the Echlin brand, part number "IR9" for $43.00
Pep Boys has the Borg Warner R-307 unit for $35.00
Duralast Wells at auto zone: $38.00 Pn: IRV307
D&M Restoration can test/repair your gauges if needed, I sent them one of mine and had the internal limiter bypassed and the ohm readings verified.
D&M
If you don't have the metal ground strap for your tank you can use a hose clamp on the sending unit neck to clamp a wire on and then use a ring terminal and self tapping screw to ground it to the frame.
Here's some more how to fix it stuff from Allpar:
link
Also, if you replace your mechanic voltage regulator on the firewall with a solid state one it will pretty much stop your gauge/light flutter (due to pulsing output from the alternator).
Here is some details on the problem: link
Depending on the year you may have an external "gauge voltage limiter" screwed to the back of your instrument cluster or it may be an internal unit that is inside the fuel gauge. My '65 has the unit inside the fuel gauge, 12v goes into the fuel gauge and then a 5v jumper wire goes over to feed the temp gauge.
Taking a reading off of your sending unit wire, a full tank will read 9 to 10 ohms, an empty tank will read 96 to 98 ohms, 1/2 tank will be 60'ish ohms. You should have a fluctuating 2-5v coming out of your gauge voltage limiter, if you put a solid 12v on those gauges you'll let the magic smoke out.
If the internal limiter is bad you can send the gauge off and have it bypassed and use an external limiter. If you have an external and its bad just replace it:
NAPA has the Echlin brand, part number "IR9" for $43.00
Pep Boys has the Borg Warner R-307 unit for $35.00
Duralast Wells at auto zone: $38.00 Pn: IRV307
D&M Restoration can test/repair your gauges if needed, I sent them one of mine and had the internal limiter bypassed and the ohm readings verified.
D&M
If you don't have the metal ground strap for your tank you can use a hose clamp on the sending unit neck to clamp a wire on and then use a ring terminal and self tapping screw to ground it to the frame.
Here's some more how to fix it stuff from Allpar:
link
Also, if you replace your mechanic voltage regulator on the firewall with a solid state one it will pretty much stop your gauge/light flutter (due to pulsing output from the alternator).
oo3- Number of posts : 290
Location : new orleans
Registration date : 2008-06-01
been there - https://vintage-vans.forumotion.com/t1077-gauge-problems - you could come by and see, however i will be out of town this weekend - oo3
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