Why is my multimeter showing "OL" where I expect to see VDC across two terminals? - JeepForum.com
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post #1 of 4 Old 01-04-2020, 10:08 AM Thread Starter
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2002 WJ 
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Why is my multimeter showing "OL" where I expect to see VDC across two terminals?

I'm trying to diagnose a non-working dome light. The bulb is the cylindrical type that looks like a fuse with with terminals at either end, and it's not blown - confirmed by both a visual and continuity check.

When I measure across the two terminals in the bulb socket, my multimeter displays "OL" rather than a DC voltage (and then drops to zero when I push the switch to turn the dome light off).

Does this indicate a short somewhere?

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post #2 of 4 Old 01-04-2020, 11:16 AM
Jerry Bransford
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OL means open loop, which is why I prefer an analog multimeter whose needle gives more of an indication of what's going on than giving non-helpful messages like that. OL means infinite resistance when the meter is in its Ohms/resistance mode.

So you have it on the appropriate DC voltage scale and it shows OL when the light should be on and the bulb is out of the bulb holder? Have you checked for a blown fuse in the fuse panel?

Here's a fair guide to the use of a digital multimeter... https://www.ifixit.com/Guide/How+To+...ltimeter/25632

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post #3 of 4 Old 01-05-2020, 08:48 AM
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Could mean overload also(more voltage than it's set for). What kind/brand of meter is it? Is it auto ranging or manual setting?
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post #4 of 4 Old 01-25-2020, 07:25 AM
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I always thought it meant Outside Limits.

When the meter sees electrical potential outside the setting parameters (limit) or outside its abilities it displays this as it is unable to read the input. You will likely see OL if you touch the leads together in a V range.

The bulb is a festoon bulb...

Typical dome lights are always powered on- the switches merely complete the circuit to (-). The action of the meter is showing ‘maybe’ a bad fuse but more likely a bad or poor connection.

Do what JB said; check fuse. If fuse is blown below doesn’t matter.

A simple test for a poor connection is to use a low-miliwatt LED test light. Very often there will be enough current to power the milliwatt LED but not an incandescent- or digital VOM.

I would also attempt to set a lower than 12V range and see if you get a result.

Another possibility is a bad relay- many newer vehicles have switches that don’t switch power- they send a signal to a module, relay bank, or computer of some sort and THAT switches the power.

I can’t see what vehicle/year this is so I don’t know what part of above is relevant. Either way, that’s enough information on things to chase to keep you out of the wife’s hair for at least a half hour.

[size=3]Shackles & D-rings are different things.
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