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Stupid Question :( !!
I need a new fuel guage but they keep asking me How many Ohms is it at full and empty. Since I just bought the boat (used) and dont know what type of sending units I have...How can I measure the OHMs?
Any ideas would be helpful
WD
Start by reading this: http://www.autometer.com/hp/
Ohms are measuring units for resistance. You measure them with an Ohm meter (big surprise there huh). Available at most auto parts stores etc for a cheapie. Most common "aftermarket" fuel gauges and senders measure 240 ohms empty, 33 ohms full. Gauge and sender must match in terms of ohm rating to work properly.
Mike,
thanks. I am familiar with OHMS and I understand resitance (ask Mrs Wet Dawg). I even have an OHM meter (DUH) but I was looking for the test method :D
Any advice as I will be getting the gaffrig from you guys.. wink
Or should I just change my sending units too?
[ March 25, 2003, 12:17 AM: Message edited by: WETDAWG ]
just connect the meter to the fuel sender and run it through it's empty/full range. (have to take it out of tank to do this). If it's 240/33 you know what you got (matches most all aftermarket gauges). ranges for other gauges are listed on the faq part of that autometer link above under fuel senders and gauges. Most boats though have 240/33 gauges in them. You normally only find other ratings in OEM auto applications etc. :)
Great,
then I'll get my face out of the PAW & Summitt Cataloges :D :D :D
Thanks Mike
I guess I have been working too late to think of pulling the unit out of the tank eek!
Wetdawg, remove the sending unit and check the resistance on the bench.If it has only one output terminal,connect the probe to that terminal and connect the other probe to the mounting flange.With the unit out of the tank you should be able to see where the leads from the wire wound resistor go to.If you want to check it in the tank, run the tank down and take readings after every 2-3 gallons added.If you have a good reading from the sending unit and it is a one wire output you may have a ground path problem.Make sure the tank has a good ground, assuming it is not a fiberglass tank,and follow the ground path back to the gauge.Also, make sure the sending unit leads are corrosion free and the insulation is in good shape. Sometimes the wirewound resistor become oxidized and you can clean it off with a pencil eraser.If you need a new sending unit,don't throw away your old sending unit until you get your new one.You will have to trim and adjust the float rod to match the old one. I am assuming the old one once worked as it should, otherwise you will have make adjustments for satisfactory readings.Be careful to note the sendng unit position when removing it so the float will have the same orientation inside the tank.
[ March 25, 2003, 01:09 AM: Message edited by: DEL51 ]
Thanks Del,
Good info
:D
WD