I’ve had a similar issue with my factory Ford GT charger. I’ve learned to work around its quirks but it definitely has some.
1. Quirk 1: It will do exactly what Kiteboarder says, going into a constant clicking/relay action that doesn't seem right and, over time, seems to not effectively charge the battery.
2. It will charge the battery up to full…and then let the batter fall down to half way, all without ever moving, disconnecting or otherwise changing anything about the car and the charger.
Sometimes the drop off in charge will be associated with the clicking (further suggesting the clicking is bad), but often it will let the charge level drop without any strange/disturbing noises.
SO — what to do, what do do…
I check on the car at least once every 48 hours (unless I’m traveling, which sadly is enough that I get a bit nervous wondering what is going on back in my garage when I’m gone for multiple days…I’ve called my wife to get status updates more than once).
If the charger shows a full charge and isn’t making scary clicking noises I leave it alone. If it is showing less than a full charge and/or making clicking noises I unplug the power cord, unplug the 12-volt charging cable from the GT, and wait about 30 seconds. Then I plug in first the charging cable and then the power cord. It always starts by showing a low charge status, but within 30 seconds moves to where it was when I unplugged it — usually either half or 3/4 of the way charged. I wait about 30 more seconds to make sure no scary clicking noises. Then I walk away.
I developed this protocol over about 6 months of hearing the clicking and/or seeing the car not fully charged after seeing it fully charged and not changing anything. Since I started following this procedure I would describe the situation as thus when I do my 48-hour checks:
1. About 50-60% of the time the charger shows fully charged with no issues.
2. About 30% of the time it shows less than a full charge (even though it was previously full and nothing changed…).
3. About 10% percent of the time it is making the clicking noise and not showing a full charge.
Interestingly, the clicking noise was far more common a year ago, but now it is fairly rare, but still happens on occasion.
One note I should add — I have a dash cam in my car that runs off the battery. It has a backup battery it uses first and it is supposed to power down if the back-up battery gets low, thus avoiding a drain of the car’s battery.
Is this device causing me to not enjoy a “set it and forget it” experience with my battery charger? Very possibly…but I was experiencing this before I installed the dash cam…
And, again, the dash cam isn’t supposed to pull the main car battery down. There’s a setting to prevent that and I’m using it.
But for now, my 48-hour check system seems to keep the battery (mostly) fully charged.