I’m having problems with my 2006 Ford Five Hundred Limited AWD CVT. The car recenty started having minor electrical surges - the headlights would brighten then dim, sometimes more, sometimes less. Then recently it started getting worse - all the lights (dash, AC system, headlights, etc) all started surging, then the check charge system light came on, and would go off. This problem would happen intermittently. When I pulled into a Ford dealer, the problem went away - and we took the car out on the road and couldn’t replicate the issue.
On the first visit the dealer replaced the battery. The problem still occurred, again and again. I took it in and they couldn’t diagnose. They checked the TSBs and tried everything listed, but nothing panned out. They think it’s a chafed wire somewhere, but don’t want to start randomly replacing things until they can figure out what’s wrong (concern is high repair costs that may not fix the problem).
I’m worried - the car is getting dangerous to drive; the speedo and tach will flip up and down when the lights go haywire, and then everything will be fine, and then everything goes haywire. The trasmission also appears to be occasionally disengaging at times (for a few seconds each time). But the last time I took it in the dealer again couldn’t figure out what was wrong, and said that until they could replicate the issue, they wouldn’t be able to do anything.
I need help! Any thoughts?
Make sure there is a good engine to body ground connection. The alternator, engine block, car body all must have the same ground. If that checks out, replace the alternator (assuming it contains the voltage regulator).
You could use a lighter plug to provide a voltage sample to a digital volt meter which you could monitor as you drive. If it EVER goes over 14.5 volts, replace the alternator. (after you have checked the ground connections I mentioned)
Are you out of warranty? Is this repair on you,if it’s warranty they must keep looking.
I had a customer with something similar,we could never duplicate so we sent them away,they were on vacation,filming out the window while driving and the car did it’s crazy instrument swings and flashes,they had us, it was on film now. I replaced the entire underhood harness (98 S-Blazer) never saw them again,hope that means it was fixed.
Sometimes in cases like yours we connected a data recorder (GM supplied) and had a record of the event.
Whenever anything electrical seems to have problems I check the ground wire from engine to body. There are different places to put them, but they always go from something metal on the engine to some part of the body. You can make a test cable with alligator clips and clip it on where it won’t tangle in anything mechanical. If the problem stops, you had a bad ground there. There are also some grounds from the dashboard going to the firewall inside. They could be near the top of the carpet.