ididieseler
Registered User
im wondering if i can hook op two oil pressure guages to one sensor, anyone tried it?
two guages from one sensor
- Thread starter ididieseler
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lindstromjd
Black Sheep
Well, first off, why?
And technically, I suppose you could. But you'd get the exact same reading on both, and the factory "sending unit" isn't a sending unit at all. It's an idiot light relay. Opens up at 8 psi, and anything after that anything you get can't be relied on as a true reading.
And technically, I suppose you could. But you'd get the exact same reading on both, and the factory "sending unit" isn't a sending unit at all. It's an idiot light relay. Opens up at 8 psi, and anything after that anything you get can't be relied on as a true reading.
jaluhn83
Full Access Member
Depends on the type of gauge / sensor, but almost certainly not.
Most electric gauges work by a magnetic field produced by the current flow through the gauge coils, then the sensor to ground. The sensor is designed typically to change resistance with temperature/pressure in a certain way - the gauge is fitted with a voltage regulator to produce a constant input voltage, and from Ohm's law the current flow through the circuit (of gauge and sensor) is proportional to the sensor resistance. The gauge is designed in such a way that this varying current flow causes a varying magnetic field that moves the gauge needle.
So if you try to run 2 gauges off one sensor you'll wind up with half the current going through each gauge (if they're both the exactly the same) and thus inaccurate readings. You could also get problems from interactions and voltage supply differences.
Some more complicated gauges (ex, Isspro EV series) use a different approach that might be adaptable, but it'd involve a fair amount of electronics work. You could probably also setup a voltmeter or ampmeter on a standard gauge circuit and use that as your 'measurement,' but it'd require a lot of interpretation and may or may not actually be useful, plus would be a very clunky approach.
The easy and simple way is 2 different gauge setups.
What exactly are you trying to do?
~John
Most electric gauges work by a magnetic field produced by the current flow through the gauge coils, then the sensor to ground. The sensor is designed typically to change resistance with temperature/pressure in a certain way - the gauge is fitted with a voltage regulator to produce a constant input voltage, and from Ohm's law the current flow through the circuit (of gauge and sensor) is proportional to the sensor resistance. The gauge is designed in such a way that this varying current flow causes a varying magnetic field that moves the gauge needle.
So if you try to run 2 gauges off one sensor you'll wind up with half the current going through each gauge (if they're both the exactly the same) and thus inaccurate readings. You could also get problems from interactions and voltage supply differences.
Some more complicated gauges (ex, Isspro EV series) use a different approach that might be adaptable, but it'd involve a fair amount of electronics work. You could probably also setup a voltmeter or ampmeter on a standard gauge circuit and use that as your 'measurement,' but it'd require a lot of interpretation and may or may not actually be useful, plus would be a very clunky approach.
The easy and simple way is 2 different gauge setups.
What exactly are you trying to do?
~John
ididieseler
Registered User
im putting a 7.3 idi in a 1978 f150, the factory guage is just a high low guage, i want to have numbers so i want to put in an aftermarket guage, i would put in a whole new setup if there is a place for another sensor but i dont think there is,
w4dsb
Registered User
put in a pipe nipple and a tee in the factory sensoe hole then screw the factory sender in to the tee and your aftermarket sensor into the other port of the tee
jaluhn83
Full Access Member
idi, there's plenty of port on the heads for sensors. About 4" below the stock temp sensor is the stock overtemp switch that could be removed and the port used, plus there's the same 2 ports on the rear of the passenger head and some others too I think.
w4dsb, I do not recommend that approach as it creates a pocket with no coolant flow so the readings may be inaccurate. You want the sensor to be in the actual coolant flow so it most accurately reads the fluid temp.
w4dsb, I do not recommend that approach as it creates a pocket with no coolant flow so the readings may be inaccurate. You want the sensor to be in the actual coolant flow so it most accurately reads the fluid temp.
w4dsb
Registered User
He said oil pressure......the pressure would be the same on either side of the tee
where did coolant come from?
where did coolant come from?
79jasper
Chickenhawk
There's two ports for oil pressure anyway.
Why even hook up the factory gauge, if you don't like the way it's setup anyways? Jw
Why even hook up the factory gauge, if you don't like the way it's setup anyways? Jw
jaluhn83
Full Access Member
Duh, good point! Somehow I was thinking temp. Apparently getting 3 hrs of sleep/night doesn't do good things to your ability to read... 
ididieseler
Registered User
im talking about oil pressure guages not water temp, i have an after market temp guage set up already using the overtemp switch
ididieseler
Registered User
where are the two ports for oil pressure?
I started a thread a week or two back...
http://www.oilburners.net/forums/showthread.php?64913-Show-me-your-oil-pressure-senders
There is a real good picture of how to tee these in.
http://www.oilburners.net/forums/showthread.php?64913-Show-me-your-oil-pressure-senders
There is a real good picture of how to tee these in.
jaluhn83
Full Access Member
Yah, sorry - brain fart. The tee will work fine.
79jasper
Chickenhawk
Back of the block between the valley lip and the bell housing adapter. Sorta towards the passenger side.
The other is on the block by the drivers side exhaust manifold flange. Rear of the coolant drain port.
jaluhn83
Full Access Member
Actually there's one more that *could* be used though I've never seen it - about 8" forward of the rear edge of the block driver's side tucked up fwd and below the oil cooler rear end assembly.
There's 5 cross passages that feed the bearings off the main oil galley and each has a plug - #1 is covered by the fwd oil cooler flange, #2 is under the motor mount, #3 is the one mentioned above, #4 is under the aft oil cooler flange and #5 is the one 79J mentioned commonly used for a turbo feed.
These are all directly off the main galley and should read somewhat higher pressure than the stock location on the top rear of the block.
Also note that the stock feed location is in a trough about 1" wide and 3-4" deep between the rear of the valley and the bellhousing adapter - the stock sensor screws into and extension piece that in turn goes into the block. Sometimes where the extension screws into the block will be loose and leak causing a mysterious oil leak from the rear of the engine. Removing this also give you more room to route a hose if you need to, though it's much harder to get to.
There's 5 cross passages that feed the bearings off the main oil galley and each has a plug - #1 is covered by the fwd oil cooler flange, #2 is under the motor mount, #3 is the one mentioned above, #4 is under the aft oil cooler flange and #5 is the one 79J mentioned commonly used for a turbo feed.
These are all directly off the main galley and should read somewhat higher pressure than the stock location on the top rear of the block.
Also note that the stock feed location is in a trough about 1" wide and 3-4" deep between the rear of the valley and the bellhousing adapter - the stock sensor screws into and extension piece that in turn goes into the block. Sometimes where the extension screws into the block will be loose and leak causing a mysterious oil leak from the rear of the engine. Removing this also give you more room to route a hose if you need to, though it's much harder to get to.
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