38 ford gas gauge
- Thread starter El Rat
- Start date
JSeery
Member Emeritus
Some people seem to get the repo sending units to work and some not. The original sending unit is a pulse type of device that worked with points. They opened and closed to regulate a current pulse to the gauge. The repo units are a resistance device. Might check the resistance from the wire by the gauge through the sender to ground and see what it reads. That might check the connections and ground.
Clem Clement
Well-known member
The last time I heard, the replacement system is of a different design. You have to change the gauge as well. I asked for a gauge in the want adds here and a fellow had a good one for sale at $15.
TonyM
Well-known member
Same here. I tried a new sending unit and no dice. Had the original 1937 Ford sending unit rebuilt and bingo--the fuel gauge worked.
JSeery
Member Emeritus
The repro senders work completely different than the originals.
JSeery
Member Emeritus
Sorry Rat, which part didn’t you understand, I could attempt to elaberate if you think it would help. You are pairing a restistance sender (the repro from Drakes) with an original gauge that was designed to work on current pulsing. The original senders provided the current pulse. The gauge moves based on a coil heating up a bimetal strip and the heat in the coil is determined by the number of current pulses it receives in a unit of time.
I think there have been some claims that you can get the repro senders to work but I do not know if there is any trick involved in doing that or not. I try to keep things matched up. Original sender with original gauges and repro senders with repro/modern gauges. And the ohm range of the sender needs to match the ohm range of the gauge.
Don't know how a 38 gage compares with a 47 merc,but a drake sender would not work on the stock gage.my sender was good,but float had cracks in it.another barner suggested cutting the stock float rod,and attaching a section of new rod and the new float by welding new rod to the old rod.I will be attempting to do this.I sealed the old float,and it floated well in water,but found out later,it will float deeper in gasoline,so no good.
JSeery
Member Emeritus
Welcome to the repro world!
Karl Wescott
Well-known member
An electronics guru should be able whip up a fairly simple solid state circuit to convert a resistance value (repro sender) to pulses.
The key information is the shape of the pulse... is the pulse width the same with different spacing between pulses, or different pulse width with even spacing, or differing amplitude of pulses within a range of pulse spacing.
Someone would need to test an original sender with an oscilloscope to find out what those characteristics are through the sender range.
The key information is the shape of the pulse... is the pulse width the same with different spacing between pulses, or different pulse width with even spacing, or differing amplitude of pulses within a range of pulse spacing.
Someone would need to test an original sender with an oscilloscope to find out what those characteristics are through the sender range.
JSeery
Member Emeritus
Interesting idea, actually the sender is providing the ground, the current comes from the gauge side and the points in the sender regulates the current flow (heat) through the gauge. The senders have points and the points open and close (vibrate) in relation to the position of whatever is being measured (temp, pressure or position).
Just did a search, these guys work on the original gauges/senders:
http://www.morrisgauge.com/