A couple of quickies
Posted: Tue Aug 21, 2018 10:13 am
Had an issue with a '13 Ford Focus. Rear lights would go batty and send false messages to information screen. No rhyme or reason. Trunk would pop open, plate, parking and brake lights would act erratically. The updated harness was installed at dealer and other shops had runs at it. It finally arrived a my door and the customer had a novel about the issues and steps taken. After about ten minutes I asked him to leave it on the front seat and expressed my gratitude for the help I may receive using it. After about 15 minutes I found the primary ground wire broken inside the harness just prior to it entering the plastic collar attached to the right trunk deck hinge. There wasn't any feedback from circuits using others as grounds so it had to be the primary. A quick wiggle test with the meter attached (I like using ohms in issues like this. I know, wicked old school but saves modules from spikes, my specialty.) If I locate the break usually both sides of it are effected by heat so I just cut it out, loop the wire I'm installing and I use weatherproof splices no matter where I'm working on a harness and another thing I'm in the habit of doing now is running my fingers along any open wire looking for bumps meaning pierced wires leading to possible internal failure. Another place voltage will show true giving false information leading to incorrect repairs.
Another one was a Maxima that the battery would die overnight. All tests showed absolutely no draw and battery tested perfect. The battery would be stone dead in the morning and this car defied all I knew about system draws. From relays down to KAM's. With my meter on and bridging the negative cable I would start getting a pulse after about 20 minutes. When I held the cable against the post I would get a contact arc and then I would settle back to it's 10 volt draw. I was getting ready to set up the meter so I would be able to calculate the amp load when it started pulsating again. I charged the battery and tested it again and it proved 90%. I got interrupted and walked away for a few hours and when I got back to it the surface charge was 11 volts. I let it sit a while longer and it dropped to 10 and remained there. What I found to be happening was at that low of a voltage a few of the power relays were booting up and staying on. I isolated those and opened them up discovering that the contact points were burned and pitted. Replace battery and four relays and everything worked great. I'm sure I'll come up with more little time savers I can share.
Another one was a Maxima that the battery would die overnight. All tests showed absolutely no draw and battery tested perfect. The battery would be stone dead in the morning and this car defied all I knew about system draws. From relays down to KAM's. With my meter on and bridging the negative cable I would start getting a pulse after about 20 minutes. When I held the cable against the post I would get a contact arc and then I would settle back to it's 10 volt draw. I was getting ready to set up the meter so I would be able to calculate the amp load when it started pulsating again. I charged the battery and tested it again and it proved 90%. I got interrupted and walked away for a few hours and when I got back to it the surface charge was 11 volts. I let it sit a while longer and it dropped to 10 and remained there. What I found to be happening was at that low of a voltage a few of the power relays were booting up and staying on. I isolated those and opened them up discovering that the contact points were burned and pitted. Replace battery and four relays and everything worked great. I'm sure I'll come up with more little time savers I can share.