I have a gas tank with a VDO sending unit in it. I have a SW gas guage in the car. Can I get these two to play nice with each other? I have it wired up right now, am suspect of the correctness of the guage readings. r
got to be sure the guage and sender are working on the same resistance or the guage will read incorrectly
That speaks to the point I was making in my original post. I don't know the resistance each unit is working on. Anybody know? r
No, but it's not too difficult to find out! Checking out the sender is easy with a multimeter. Just take a reading with a multimeter with the sender at its "full" and "empty" positions. The gauge itself is a little more involved. You'll need a decade box (it's a box with variable resistance potentiometers). The decade box it connected to the gauge in place of the sender. Once power is hooked up, you can vary the resistance to gauge until you get a "full" reading. Do the same for an "empty" reading. This will establish the operating range of the sender you need. It probably sounds involved, but it's really easy!
Tough to know without model numbers. Some go low to high resistance as tank empties, others go high to low. Plus resistances are different from manufacturer to manufacturer, so it's a crapshoot when you start mixing them. The sending unit is pretty easy to figure out with just an ohmmeter. The gauge is a little more difficult, as you have to apply voltage through a milliampmeter (sensitive ammeter) and then vary the current, take the readings, do the math, etc. It can be done, but it's nothing that Goober or Gomer over at Wally's filling station is going to be able to figure out. Can you tell I'm an Andy Griffith fan?
I had the same deal in my Model A. The previous owner had VDO sending in the trunk, then paneled & carpeted over everything so I couldnt get to it. Went through the hoops with VDO, SW and the place in riverside that can rewire guages... Final answer was.... Wouldn't work. Had to bite the bullet, take everything out and put in SW sending unit. Wasnt too bad. I had the White faced Wings and an aweful set of the Cockpit Royale... The name just gives you shivers doesnt it! Hyfire
SW uses senders with resistance of 240 ohms empty , 33 ohms full standard VDO uses 10 empty and 180 full..although they do make senders to match the SW gauge the best bet is to take an ohmmeter and check your sender
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