connecting senders to gauges

[Simon]

I want to test that the senders and fuel gauges I have work together. Neither are in the car, I just want to "jerry rig" them together and move the sender up and down to see if the gauge registers correctly.
How do I do that?
Thanks
Simon

smiths gauges, unknown senders, one has three spade terminals, one has two!!!!!!

 

[Ron Earp]

Connect the senders to the gauge. Supply 12V to the gauge. Attach the ground (Earth for you Limeys) to the gauge and the sender. Move sender arm, watch needle move.

 

[Frank Catt]

Ron, add that you must "ground" the sender to the negative side of the 12V supply, Frank

 

[Simon]

HHHMMMM, did that, all seems to work ok apart from the gauge reading back to front

 

[Simon]

OK, both gauges work ok, one of the senders works the right way round and one works back to front. Changing the wires around on the sender gets pops and sparks from the sender unit (glad I'm not doing this in the tanks!) the sender units are slightly different, maybe I have one that gives a different signal to the other?

 

[Chuck]

Simon: Don't change the wires on the sender. Simply remove it, flip it over, and put it back on. The sending units are usually 'upside' down since the gauges, likewise, are set up 'upside down.' Actually both sending units should be reversed, so make sure both are reading correctly. More details on my blog.

Also, when pre testing the wiring it is a good idea to use a batter charger rather than a battery. The charger should be breaker or fuse protected against short circuits.

 

[John P]

Also, when pre testing the wiring it is a good idea to use a batter charger rather than a battery. The charger should be breaker or fuse protected against short circuits.

I've always used a 12V lantern battery to test circuits. It has 12 volts available, but very little current to hurt anything in case of a short, and no circuit breakers to reset. I've also heard that a battery charger isn't a true 12 volt DC current and may damage some electronics, if using it without a battery in the circuit.

 

[Jim Rosenthal]

Some Smiths' gauges use the sender in series with the gauge. Some Smiths' gauges also use a voltage regulator to supply a lower voltage to the gauge/sender combination. My Smith's gauges came with a (crude) wiring diagram which shows this. This is a different arrangement from what I'm used to, where you have three wires to the gauge- a 12 hot, a ground, and a signal wire (plus another hot for the lamp in the gauge). The Sender will have two connections- usually a ground through the engine block, and a signal wire. The other end of the signal wire is going to the gauge, as noted. As I understand it, what the gauge is doing is comparing the 12v supply with a modulated voltage from the sender. Smiths' gauges are sometimes set up differently.

 

[Simon]

HMMM, I think it's the sender and not the gauge. BOTH gauges are the same, both gauges work correctly with one of the senders, but the other sender make BOT of the gauges work back to front. They are top mounted senders.

 

[Jim Cowden]

HMMM, I think it's the sender and not the gauge. BOTH gauges are the same, both gauges work correctly with one of the senders, but the other sender make BOT of the gauges work back to front. They are top mounted senders.

It does sound like the sender.
Simon put an ohms meter on the sender and see if it reads back to front from the sender that works OK.
That will confirm sender fault.

Jim

 

[Bill Musarra]

Might I suggest that anyone doing any wiring of their cars needs to test the wiring before going full blast with a battery that will give you upwards of 150 amps surging through a snakes nest of wires. If there is a short, you will not only fry that wire, but anything in close proximity(other wires) not to mention the fire/explosion hazard. Go the extra expense and get a dedicated 12 volt power supply. They come in various amperage. I got mine with 6 amps. When hooking up a circuit to test, it does so, maybe not the full power to the circuit but the knowledge that it works the way it is supposed to and not blow any fuses. Most are internally fused, so that any pops and crackles will trip the breaker(most automatically reset) and you don't have to worry that something else has fried. Most go for about $25-$75. Test each circuit first, find the errors, THEN hook up that mega battery. When something doesn't work the first time, the most errors are in the grounding of the item in question. It is easier to find the one fault than three or four all at once. Good examples can be found all over the net. Here are some I found in a minute using "12 volt power source" through Google.

Pyramid 12 volt DC Power Supplies

Bill