The Stovebolt Site Forums The Shop Area The Electrical Bay Connecting gas gauge/sending unit of different types.

As I have a tendancy to push the envelope I now find myself asking an electrical question. I am connecting a GMC sending unit to a Toyota gauge. When I hook them up as per the schematics the gauge reads "F" when I move the float up and down it has little or no effect. When I put an Ohmeter across the disconnected sending unit it reads 0 ohms or close to it, it seems to be a hit and miss situation with the wiper not always making contact with the windings of the resistor - also I only have a 1k meter.

My basic question is, does the meter read current or voltage?

Just to make sure I have it connected correctly.

Does the "ground" side of the sender connect to battery negative? and then the other side of the sender go through the gauge to positive?

Thanks in advance.

You are probably going to have to come up with some sort of weird adapter circuit, but I have no idea what the resistance range on your Toyota gauge is. The easiest way would be to find a sender from the same type of Toyota as the gauges came from.

An Ohmmeter measures resistance, not current or voltage. An Ammeter measures current, a voltmeter measures voltage. Your standard hand-held multimeter will do all of these, with several ranges for each.

Your connections sound right, the main problem is the dissimilar gauge and sender. Once again, the easiest way to correct this is to find a way to install the Toyota sender in your gas tank.

GMCpanel thanks for the reply. I guess I wasn't clear enough. I was wondering if the gas gauge meaured volts or current, seems to me that by the cicuit configuration it would have to be current and the gauge is in series with the sender. I guess I be looking for a toyota sender to adapt.

The way I understand it, gas gauge senders use a rheostat (or something of that sort) that changes resistance with the level of the fuel. This should clear up any confusion on this issue: http://www.howstuffworks.com/fuel-gauge.htm

According to this, the gauge measures the current, albeit in a rather unusual manner.

Different automakers use different ranges of resistance in their senders, making the fuel gauge mix-and-match nearly impossible. They don't even read the resistance in the same direction, with some manufactures low resistance is full, others use low resistance as empty.

When testing your sending unit, you will use an ohmmeter.You should get a variable reading from 0 or 1 to 30 ohms (for example)as you move the float arm of the sending unit.