Expert: Ernest (Ernie) Kenward - 12/19/2008

Question
Last Friday my 2002 RSX had its first electrical problems ever. For 5 minutes in the middle of a 2 hour drive, the needles on the gauges were going crazy and the radio was turning on and off (mostly off). At the end of the approx. 5 minutes, everything was fine. I went out to dinner later that night and on the ride home, the lights starting dimming and the car just died on the side of the highway. I had the car towed to a Honda dealer, as the following day was Sat. and to my knowledge no Acura dealers were open. The dealer replaced the battery and thought that they solved the problem.

When I picked up the car at closing on Sat., the car ran fine. Within about 10 minutes of driving, the check engine light came on, denoting, according to the users manual that something was amiss with the emissions system.

I had just had emissions testing the Monday prior and the car passed easily.

The next morning (Sunday) when I started the car, the check engine light was still on and the check battery light was also on.

I took the car back to the Honda dealership on Monday morning. Halfway to the shop, the check battery light went off. The dealer took the car for a ride and the light never came back on. They also ran some diagnostics on the electrical system and said they found nothing wrong, however one of the 02 sensors was bad.

Not having much faith in the Honda dealer, I brought the car to the Acura dealer. They replaced the O2 sensor and also the serpentine belt for the alternator.  

I was away, so my wife picked up the vehicle on Tuesday night. It ran fine for her from Tues. night until Thursday morning when she drove my car to work and the gauges starting going crazy again and the radio went on and off. She drove it back to the Acura dealer and now they're saying that the car needs a new alternator.

I'm not sure whether or not the alternator is the problem and I hate to pay for its replacement if that isn't the problem.

The dealer said there was also some evidence of mice having been in the engine compartment, but said they didn't do any major damage.

What do you think is causing my trouble? Thanks for your help.

Pete

Answer
The only realistic advice that anyone can give you from a distance for any problem of a random and intermittent nature is that the car needs a systematic and thorough investigation of its electrical system.  One or more key circuits, likely power distribution circuits, is intermittently either becoming open-circuited, or is shunting to neighbouring circuits or to the vehicle common, most likely via a short circuit to the body or chassis.

Inasmuch as the presence and activities of rodents has been detected, my instinct is that you or a good investigator will find gnawing damage to one or more harnesses or perhaps connectors, and this type of damage could certainly lead to the problems you have been experiencing.

A thorough investigation would include close visual inspection of all those circuits that are readily accessible to sight, and multimeter (with low-ohm range) testing of continuity within circuits and verification of insulation  between circuits which should be isolated from each other.

Regarding isolation: while I believe that alternators can be discounted as a cause in the bulk of the problems of this type, there is one plausible scenario in which an alternator can create wild voltage transients, transients which can cause erratic operation.  If the field rotor has an intermittent fault in its insulation, especially a short to the rotor's frame and hence to the chassis, the voltage regulator output that drives this field typically will oscillate at a rapid rate between high field current into the fault and off again as its short-circuit protection circuit cycles on and off; this will cause an alternator output that is both erratic and high amplitude.  

If this IS a problem, it usually will not manifest itself until the alternator has warmed up after a period of driving; the thermal expansion caused by the warming will bring the conducting surfaces together through the damaged insulation.  Checking an alternator for this type of problem could be done by monitoring its output using a lagging multimeter or - better yet - a scope.  Should the described problem exist, the alternator output would change from being a more-or-less constant DC level (14.2 to 14.3 V initially to about 13.8 to 14.2 after normal warm-up) to what could best be described as a "very sawtoothy waveform of random amplitude", coincident with the appearance of the symptoms you have described.

I do think, however, that the electrical harnesses will turn out to be the culprit in this case.

Depending on your own electrical skills, you may want to get the car's electrical diagrams (OEM or Mitchell's Online) and take the bullwork of this task on yourself.  Alternatively, you might check with fleet operators to get a recommendation to a good independent auto-electrical specialist to take this task on for you.

Good luck and happy hunting ... EGK