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HJ60 oil pressure sender



Roman, thought this may be of interest
I have just taken the old HJ60 oil pressure sender unit apart. Have
uploaded pictures to
It has a lower contact connected to earth, moved by the brass diaphragm.
Above this is a contact on a bi-metallic strip with a heater wire wrapped
around it. The size of the gap between contacts is adjustable via the white
plastic adjuster. The heating coil is in parallel with an 820 ohm wire
wound resistor. Total resistance of 112 ohm. The voltage feed from the
gauge connects to the resistor and heating coil. Current only flows when
oil pressure is up and the contact is closed, this in turn heats the coil
and pulls the contact open. The greater the oil pressure, the faster the


On 6/4/05, Neil Paisnel <[Email address removed]> wrote:
Great stuff. I never had a chance to take a sender apart. I was under
the impression that the sender is some sort of variable resistance
gizmo that changes with the pressure.
Now it looks to me that it is the frequency of the ON/OFF cycles that
affects gauge readings. But is pressure translated into binary signals
without being affected by engine speed?
The membrane closes the contacts as soon as there's minimum pressure
in the system but with increasing engine revs the gauge no longer
measures pressure but oil pump speed? Am I correct?
Roman (London, UK)
'92 HDJ80