MG CAR OWNERS FORUM

I've had the car for six years, and I absolutely love driving with the roof open. The car's ability to open and close the roof is absolutely mind-blowing. I always thought that would be the first part to break, but I haven't experienced any problems with it. 51630 is a relatively low mileage for the year.

A new thermostat was installed after the red warning light and limp mode were activated in January by the garage I took it to. Just like another user on the forum, I've recently had the same issue in slow traffic. The car drove smoothly after turning off and starting again. Even in slow traffic yesterday, turning off and then starting again didn't fix the problem. Pulling in and donning the hazards was something I had to do multiple times. We made it home safely after I got up and running and drove it swiftly. I noticed that someone else also mentioned that I'm now receiving the "key card battery low" message. Since the message persists after inserting a fresh battery into the key card (which came from a 4-pack), I will attempt using a fresh battery first and provide an update. I would be eternally grateful for your assistance.

Your limp mode is unrelated to the keycard battery, which solely powers the remote locking.
The first step should be to get a diagnostic scan.

I really appreciate it; I had no idea it had anything to do with the big issue. After a few MOT warnings that the battery wasn't 100%, I finally got around to fixing it, reasoning that the car would just say "start engine battery low" when it needed charging. Therefore, I looked up whether an old battery could be at fault on Google and found that it could be. The reasoning behind this is straightforward: a strong battery won't be needed when it's moving quickly, but a weak battery won't be able to compensate for slow speeds. I will provide an update after tomorrow when I get one fitted.

My apologies, but "the car tells me" is the correct expression.

Everything goes wrong when the battery dies. At most, I swap out mine every four years. It may last another year now that I have it set up on a permanent trickle charge.
This is an excellent starting point, but if yours is younger, you might have additional issues.
As an aside, running at low revs is perfectly fine for the alternator when charging the battery.
Take a look at the battery voltage first thing in the morning before you set out on your journey; anything below 12V raises suspicions.
Checking the voltage at idle—which should be about 14.5V—is a good way to test the alternator. After that, you can turn on the heater fan and the voltage and lights should remain relatively constant. A possible defect could be a significant drop.