Rob, Interesting Electrical Tidbit

[randyp]

Rob, I just read an article in Popular Mechanics magazine, car repair section. A consumer wrote in about having to replace front CV joints and wheel bearings bout every 6 months and dealer could not figure out why they kept failing. He said they would start making unusual noises very soon after replacement, then shortly after, fail again, dealer mechanic was stymied. PM magazines diagnosis, which they also said was not that unusual, is that the car had a bad grounding strap or maybe two, so current was finding an easier, lower resistance path from engine to chassis passing through the wheel bearings, axles, and CV joint internals. The high current, transmitted through small points of contact between the machined races and the rollers or balls, strikes tiny arcs, damaging the smooth surfaces. Within a few hundred miles, the joint or bearing fails. I have always been careful welding on trucks, bout where locating ground, so as not to route current through wheel bearings. I thought was an interesting article, a lil unusual, but worth passing on. You gave a good dissertation in a post good while back bout importance of good clean, tight electrical connections, so, there you go Dr. Rob! randyp

[Rob]

Rob, I just read an article in Popular Mechanics magazine, car repair section. A consumer wrote in about having to replace front CV joints and wheel bearings bout every 6 months and dealer could not figure out why they kept failing. He said they would start making unusual noises very soon after replacement, then shortly after, fail again, dealer mechanic was stymied. PM magazines diagnosis, which they also said was not that unusual, is that the car had a bad grounding strap or maybe two, so current was finding an easier, lower resistance path from engine to chassis passing through the wheel bearings, axles, and CV joint internals. The high current, transmitted through small points of contact between the machined races and the rollers or balls, strikes tiny arcs, damaging the smooth surfaces. Within a few hundred miles, the joint or bearing fails. I have always been careful welding on trucks, bout where locating ground, so as not to route current through wheel bearings. I thought was an interesting article, a lil unusual, but worth passing on. You gave a good dissertation in a post good while back bout importance of good clean, tight electrical connections, so, there you go Dr. Rob! randyp

I've actually seen this phenomena a couple times in the past with import nameplates. Both had to do with extra stereo equipment installed aftermarket with insufficient grounding. One car was a Honda Civic, the other a Mitsubishi Evo. When you get into strong current draw there has to be effective grounding from the battery to frame, engine, and equipment or attachments as a continuous loop.

Current carried through a rotating mass, (such as roller bearings) will quickly "gall" the friction surfaces and destroy the bearing itself.

Thanks for the post.

Rob

[mackmixer]

This also applies when you are electric welding on trucks or equipment.

Don't put your ground lead where you will have a welding current passing thorough a bearing...

[Rob]

This also applies when you are electric welding on trucks or equipment.

Don't put your ground lead where you will have a welding current passing thorough a bearing...

On cars with an ECM, (1984 and newer, therabouts) I always take the battery cables loose before welding. I've never burnt anything up electronic, (so far).

Rob