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Dec 6, 2013 | 10:16 AM

#31

Gary Lewis

FTE Legend

Joined: Jul 2010

Posts: 32,875

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From: Northeast, OK

I'm confused. If he has the rear harness disconnected then how does he have "normal voltage to the plug, but not to the lights"? And, does the fuse hold with that?

Dec 6, 2013 | 10:20 AM

#32

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

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From: EXTREME southwest CT

If he has normal voltage to the harness plug with it disconnected, but is only seeing 9.7V at the sockets before the fuse blows, something is sucking the rear harness portion down.

At least that's what I make of it.

Wish West Haven was closer.
I could go fix that up.

Dec 6, 2013 | 10:28 AM

#33

Gary Lewis

FTE Legend

Joined: Jul 2010

Posts: 32,875

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From: Northeast, OK

I missed the 9.7 volts and the fuse blowing part. But, if that's what is happening then there is obviously a problem with the rear harness, and most likely the botched trailer connector is the culprit. But, to only pull it down to 9.7 it isn't a dead short. I think I'd put an ohm meter from the brown wire to ground, with the harness disconnected, and watch the meter as I move the harness around. Can't imagine it won't flicker quite a bit, but that's one of the problems with most DVM's - the digital readout makes it tough to watch connections change.

Dec 6, 2013 | 10:34 AM

#34

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

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From: EXTREME southwest CT

My mistake, 9.5V, in post #14

Dec 6, 2013 | 10:41 AM

#35

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

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From: EXTREME southwest CT

Quote:

Originally Posted by Gary Lewis

I'd put an ohm meter from the brown wire to ground, with the harness disconnected, and watch the meter as I move the harness around.

I thought I suggested removing the bulbs and testing between the harness+ and ground.

This is one of those situations where my old Simpson 260 is a far better diagnostic tool than a DMM.
The needle will react much quicker than an LCD display.
If your DMM has a bar graph setting, you may want to use it.

Dec 6, 2013 | 10:58 AM

#36

Gary Lewis

FTE Legend

Joined: Jul 2010

Posts: 32,875

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From: Northeast, OK

You did suggest that, and I should have said "as Jim suggested". Sorry.

Yes, the bar graph or an analog meter (that Simpson is wonderful!) makes it much easier.

Dec 6, 2013 | 11:03 AM

#37

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

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From: EXTREME southwest CT

I'm not looking for 'credit', just wondering if I hadn't been clear?

Poking things around can help you find the fault but it is MUCH easier to find a constant than an intermittent short.

The old 260 is an heirloom I really cherish.

Dec 6, 2013 | 11:41 AM

#38

Gary Lewis

FTE Legend

Joined: Jul 2010

Posts: 32,875

Likes: 48

From: Northeast, OK

No, you were clear - I just overlooked it. Pulling the bulbs would be Step 2, right after unplugging the harness.

Having said that, your 260 would easily see the difference between a couple of bulbs in parallel and a short on the tail light circuit. I used one of those about 44 years ago and still remember how well it worked.