Last year I had a problem with a defective electrical connection on the fuse box of my 98 Legacy Postal. In the process of tracing the bad wire, the dealer used one of those electrical probes that pierces a small hole in the wire when checking connectivity. They found and fixed the problem but this past week I started having the same problem again plus other things started acting intermittant and then stopped altogether. I started tracing the wiring and found that in the center of the car under the radiator there is a wiring harness with a number of wires in it. Four of them were broken. Apparently this winter water got into the harness and made its way into each of the tiny holes poked into the wire by the technician. The wires then corroded - the copper turned green and then brown when it burned through. I suspect the corrosion took place so fast due to the fact that this area uses lots of salt on the roads in the winter and that this got to the wire. I talked to the Subaru dealer about it and he just shrugged and said that the normal way to troubleshoot and he never heard of anyone ever sealing up the holes poked in the wires.

The reason for this posting is just to provide a warning to any of you that use the probe type continuity checkers. If the wire you are checking is down low on the car and subject to getting wet, be aware that water can get into the wire via capillary action and will destroy the wire in short order. I replaced the wires, taped them and coated them with a liquid rubber goo and everything appears fine now. I am wondering if anyone else has had this same experience?

 

John C.

not for years as I live in CA now, but it was common on large commercial trucks and busses that ran cross country. It really ruins the wires when a tech does that in an exposed area.

[...]Apparently this winter water got into the harness and made its way into each of the tiny holes poked into the

wire by the technician. The wires then corroded - the copper turned green and then brown when it burned through. I suspect the

corrosion took place so fast due to the fact that this area uses lots of salt on the roads in the winter and that this got to the

wire. I talked to the Subaru dealer about it and he just shrugged and said that the normal way to troubleshoot and he never heard of

anyone ever sealing up the holes poked in the wires.

Puncturing insulation in order to check continuity isn't a good practice. It's usually done, unfortunately, to save the tech some time. Sometimes the saved time will be passed on to the customer as cost savings. In my opinion, unless connectors are very difficult to get to, back-probing them is the better approach, even if it means a few minutes/dollars more.

 

I've never had (on my own cars) wire conductors damaged by intentional punctures. However, I've experienced corrosion as you described due to accidentally damaged insulation combined with road-salted water, so your concern makes sense.