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Old 06-11-2010, 03:43 PM
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CardinalFJ60 CardinalFJ60 is offline
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Default How do I bench test the oil press gauge?

I pulled the cluster out of the 40 to re-do the lights and other general spruce up things. the Oil pressure gauge has never worked. I put in a new sender and used gauge while ago and still no workie. While it's out, I'd like to test things from the cluster back to the sender.

How do I bench test the gauge?

I looked in the FSM and it shows how to test it when still hooked to power in the vehicle. I need to do that test on my bench, but don't know how/where to get power to it with my extra battery.
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Old 06-11-2010, 09:30 PM
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TIMZTOY TIMZTOY is offline
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If it's all electric. The gauge should be a risistor type gauge. As the pressure rises the ristance lessens. (I think) with it off the car you could try hooking up the ohm meeter. And move the needel. The risistance should change. If it's oil. Don't know other than check the oil line

all that info is general electrical test. Nothing to do spasfically with 40's
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Old 06-12-2010, 12:00 AM
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Quote:
Originally Posted by CardinalFJ60 View Post
I pulled the cluster out of the 40 to re-do the lights and other general spruce up things. the Oil pressure gauge has never worked. I put in a new sender and used gauge while ago and still no workie. While it's out, I'd like to test things from the cluster back to the sender.

How do I bench test the gauge?

I looked in the FSM and it shows how to test it when still hooked to power in the vehicle. I need to do that test on my bench, but don't know how/where to get power to it with my extra battery.
Hi Shawn,

The oil pressure gauge is basically an ammeter. It is connected to system + on one side and to the sender on the other side, the sender is grounded on it's other side. The sender will give less resistance to higher oil pressure, and thus deflect the gauge.

The coil inside the gauge is fairly sensitive. If you connect 12 volts across the terminals without the sender to limit the current you will fry it instantly. Like a fuse.

To check it on a bench you will need a DC power supply and some kind of current limit in series such as a power resistor of similar ohms as mid point of the sender's resistance. I'd look it up but my manuals are in the garage, and I'm not. My guess would be that the sender's resistance would be on the order of 50-200 ohms, because that would be a typical value for the sensitivity of our gauges. Beware of using a potentiometer to simulate the sender! If it is all the way to one end it will be a short and you will fry the coil! If you do use a potentiometer to modulate the current, always start at midpoint to avoid that.

Rather important to observe proper polarity on the bench test: these mechanical gauges can be easily damaged with reverse polarity applied to the terminals.
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