Temperature and oil pressure senders
- Thread starter 47Merc
- Start date
flatheadmurre
Well-known member
This has been debated a few times...
Stock gauges are current driven bimetal and not linear...they work as mirror images of each other the sender/meter.
The problem is that if you want to drive it with a resistive sender it has to nonlinear following the movement of the bimetal.
So early ford instruments are in the 70ohm range but not very happy with resistive senders.
So if you really don´t want what´s there original...what can be done.
VDO had instruments with the same buildsize as early KS.
The cheap and common stuff around here was Volvo 240 series(VDO only and not Yasaki) that can be fitted behind the scale of a ford turning it into 12v using volvo senders.
Or aftermarket ones in the 240ohm range.
The senders/meters come in 0-240 or 240-0 so mix them correctly or the meter moves backards.
Keeping the original stuff and a voltage reducer is the easiest way to go imho.
Stock gauges are current driven bimetal and not linear...they work as mirror images of each other the sender/meter.
The problem is that if you want to drive it with a resistive sender it has to nonlinear following the movement of the bimetal.
So early ford instruments are in the 70ohm range but not very happy with resistive senders.
So if you really don´t want what´s there original...what can be done.
VDO had instruments with the same buildsize as early KS.
The cheap and common stuff around here was Volvo 240 series(VDO only and not Yasaki) that can be fitted behind the scale of a ford turning it into 12v using volvo senders.
Or aftermarket ones in the 240ohm range.
The senders/meters come in 0-240 or 240-0 so mix them correctly or the meter moves backards.
Keeping the original stuff and a voltage reducer is the easiest way to go imho.
big job
Well-known member
All I know is temp senders are finicky. But the oil sender. I have a mechanical gauge
(previous owner put there 1946 same as 47-48) when warm mechanical says 40lbs
and the dash says a touch under 30? So, to my junk draw I come up with 1970's or so
Mopar senders. Same thread, now the dash gauge is over 30lbs. pretty close to 40.
My question to all; these engines to 1953 have 80lb senders. OK my math is bad but
80 divided by 2 is 40 right: so why since day one all are 0 - 30 - 80????? My 1953 and
up trucks say 0 - 40 - 80 (don't know about 53 cars) but my trucks still have the usual
flathead senders . All I know is early V8s should be 50lb pumps, unless changed.
If so you need 50lb sender . Post says 1948 gauges then says EV8? me dumb whats
EV8 should be a 59 A 239 thats 80lb oil pump......sam
or I'm having a senior moment ?
(previous owner put there 1946 same as 47-48) when warm mechanical says 40lbs
and the dash says a touch under 30? So, to my junk draw I come up with 1970's or so
Mopar senders. Same thread, now the dash gauge is over 30lbs. pretty close to 40.
My question to all; these engines to 1953 have 80lb senders. OK my math is bad but
80 divided by 2 is 40 right: so why since day one all are 0 - 30 - 80????? My 1953 and
up trucks say 0 - 40 - 80 (don't know about 53 cars) but my trucks still have the usual
flathead senders . All I know is early V8s should be 50lb pumps, unless changed.
If so you need 50lb sender . Post says 1948 gauges then says EV8? me dumb whats
EV8 should be a 59 A 239 thats 80lb oil pump......sam
or I'm having a senior moment ?
flatheadmurre
Well-known member
The meter just knows 0-max it doesn´t know what it measures or in what range.
So using a 50lbs sender means you need a 50lbs scale on the meter to match.
Problem is a bimetal isn´t linear so the easiest solution was probably to just check how much pressure it took to get to middle of scale instead of trying to make a more linear bimetal..
So using a 50lbs sender means you need a 50lbs scale on the meter to match.
Problem is a bimetal isn´t linear so the easiest solution was probably to just check how much pressure it took to get to middle of scale instead of trying to make a more linear bimetal..
JSeery
Member Emeritus
I've never tried it, but I don't think a resistance sender would work with the original gauges. The original senders use contacts that open and close to regulate current, so you end up with a pulsed current through the gauge. This varies the current which varies the gauge reading. A resistance sender varies the current by varying the resistance. As has been pointed out, you might be able to get it to work correctly at the extremes, but it would be difficult to match the pulsed current curve in between.
Easiest way to use the original gauges and senders is to reduce the voltage to the gauges to 6v.
Easiest way to use the original gauges and senders is to reduce the voltage to the gauges to 6v.
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