Bench Test Engine Harness

[87mj]

I have been in the process of stripping a car to it's shell.  The wiring harness is removed and the engine will be pulled soon.
While I am waiting in queue at the body shop, I thought it would be a great time to check and fix any electrical problems in my wiring harness but electrical circuits are not my strong suit. 

Is there a way to apply power to an engine harness by using an external source such as the battery or an external power supply without burning it up?  If I can do that, thought I could bench test connectors, headlights, taillights, dash, etc and fix anything before I install it back in the car.

Thanks
Gary

[Matthew Abate]

I’m wondering the same thing.


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[Captain Obvious]

Of course every car is different, but I've found the majority of electrical problems come from two sources:

1) Dirty or loose contacts
2) Previous owners

The wires inside the harness should be pretty much trouble free unless they have been overheated in the past and melted through their insulation.

If all the terminating contacts in the connectors and devices they connect to are clean and tight, and there are no signs of previous owner mods (hacking, cutting, changing the harness), then my inclination would be to try the original harnesses and see if they work.

To do a quick and dirty test for gross problems, you can connect all the harnesses together out of the car and connect to a current limited power source and see what happens. Maybe install a couple key components like the dash and ignition switch. And with all the history of problems with the headlights and turn signals, I would take a good look at the control stalks too.

[JSM]

What CO said above. 

Also, it’s good to admit your limits. Since you were honest already, I would focus on the connectors and wires themselves and not apply any power. The last thing you want to do is add power, have mistakenly missed covering a hot wire and accidentally fry the whole harness. 

You can add a lot of life reducing resistance in poor connections. Steel wool, electrical cleaner, emery cloth, cut finger nail files can do a lot. 

Hopefully, you were super anal, labeled and photo everything. Engine harness is easy, but the under dash wiring can get messy.