SL/R230: Voltage regulator replacement
Thread Starter
Member
Joined: Jan 2003
Posts: 185
Likes: 18
From: Cedar Park, Texas
2013 Porsche 911 Carrera 4S, 2004 SL55, 2012 Lexus IS250, 2021 Toyota Highlander
Voltage regulator replacement
I've ironed out the BCM issue that I had thanks to the SL guys, but now I've got a red light battery warning that comes on again. The lights pulsate and I can hear the hum of the ac rise and fall. When I read the voltage from to both batteries they look fine at around 14V. I'm thinking it's a voltage regulator and I raised the car today and I could see the regulator but what I can't find a picture of is how to take the cover off to get to the screws to remove it. Anybody have picture of what the cover looks like attached. I'm trying to figure out if I need a screwdriver to remove the cover or a socket. It looks fairly straightforward once you get the cover off. Any guidance would be greatly appreciated.
Thread Starter
Member
Joined: Jan 2003
Posts: 185
Likes: 18
From: Cedar Park, Texas
2013 Porsche 911 Carrera 4S, 2004 SL55, 2012 Lexus IS250, 2021 Toyota Highlander
Thanks. This helps. I also felt a screw near the top (or side considering the way it's mounted). Correct? Just wanted to get my bearings straight before I tackled it.
Junior Member
Joined: Oct 2025
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Likes: 8
I've ironed out the BCM issue that I had thanks to the SL guys, but now I've got a red light battery warning that comes on again. The lights pulsate and I can hear the hum of the ac rise and fall. When I read the voltage from to both batteries they look fine at around 14V. I'm thinking it's a voltage regulator and I raised the car today and I could see the regulator but what I can't find a picture of is how to take the cover off to get to the screws to remove it. Anybody have picture of what the cover looks like attached. I'm trying to figure out if I need a screwdriver to remove the cover or a socket. It looks fairly straightforward once you get the cover off while also searching Houses for rent in Greece for another project. Any guidance would be greatly appreciated.
Thread Starter
Member
Joined: Jan 2003
Posts: 185
Likes: 18
From: Cedar Park, Texas
2013 Porsche 911 Carrera 4S, 2004 SL55, 2012 Lexus IS250, 2021 Toyota Highlander
Something interesting has happened. While I couldn't remove the voltage regulator because I couldn't feel my way around to find the screws but I was able to remove the nuts that were holding it down. I put them back on and turned on the car to make sure I didn't mess anything up, and now the battery warning has gone away. It would come on and off several times during a short drive. I haven't seen it in a few days now. Is it possible that it was the connection to the voltage reg instead of the voltage reg itself?
Super Member
Joined: Sep 2021
Posts: 546
Likes: 118
From: Ann Arbor, MI
2004 SL600
The fact that you got 14V made me think the regulator and alternator were OK. It sounded more like a bad connection as mentioned in post #5. Or that the replacement BCM was sending mixed signals.
Hopefully your work in the area fixed it.
Hopefully your work in the area fixed it.
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Thread Starter
Member
Joined: Jan 2003
Posts: 185
Likes: 18
From: Cedar Park, Texas
2013 Porsche 911 Carrera 4S, 2004 SL55, 2012 Lexus IS250, 2021 Toyota Highlander
To add to this mystery, I've noticed a trend. I only appear to be getting the red battery warning when using keyless go. When it insert the key, I haven't been getting the warning. I do notice that when using keyless go, I sense that the starter seems slower to start the car. When I use the key, it's almost immediate.
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Super Member
Joined: Sep 2021
Posts: 546
Likes: 118
From: Ann Arbor, MI
2004 SL600
What was your BCM issue?
Makes me wonder if the K57 relay is engaging due to the BCM "thinking" there is an issue. This is causing the front battery to power the entire car; hence the slower cranking. And the Red Battery warning because the BCM is reporting an issue.
Makes me wonder if the K57 relay is engaging due to the BCM "thinking" there is an issue. This is causing the front battery to power the entire car; hence the slower cranking. And the Red Battery warning because the BCM is reporting an issue.
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