Radio Shuts Off Under power
06-10-2010, 04:52 PM
#16
Rennlist Member
I have seen this exact problem and very likely it is your voltage regulator. The radio has a protection circuit (Zener diodes) built into the system to shut down in case of over-voltage. I suspect your radio is a newer unit.
If you keep doing this, you are likely to damage the DME and cook your battery.
Please put a volt meter on the battery or cigarette lighter and repeat the test. I suspect your voltage will be greater than 16V.
If you keep doing this, you are likely to damage the DME and cook your battery.
Please put a volt meter on the battery or cigarette lighter and repeat the test. I suspect your voltage will be greater than 16V.
Speaking of which,...and it was a long time ago.............................I recall looking through the DME prints (yes, I can read them quite easily), looking for what Porsche did as to circuit board overvoltage protection and don't recall seeing any.....at minimum, I thought they would have installed a simple zener circuit (ess'y: component is all)...but surely no protection circuitry. This is from recollection, mind you.
This thread has sparked my interest in revisiting this DME analysis so off I go,...and look for mods to protect it from such an event...Thanks for reminding me............
I'm sure others will chime in on this notion.....if Lorne's reading, we'll know shortly, the details.....let me see if I can beat him to the punch (although I doubt it).
Best to you,
Doyle
06-10-2010, 05:36 PM
#18
Instructor
Thread Starter
Join Date: May 2009
Location: By the Bay, Maryland
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
Thanks, I ordered a new VR today and will install. I am thinking I should just replace the Alternator as well since I do not know if it was replaced and I have 130,000 on the car now.
06-10-2010, 05:39 PM
#19
Rennlist Member
Doyle
06-11-2010, 09:57 AM
#20
Race Car
Most mercedes cars through the 80/90s have whats known as an overvolt protection relay. they fail all the time and cause minor starting problems. Possibly a simple integration of one of these relays into the wiring harness would be all it takes. Just a thought I had. If I can help with any research on this, I will. I can get part numbers, and I probably have a wiring diagram for any of the Benz cars that have this, along with input/output voltages.
06-11-2010, 01:30 PM
#21
Rennlist Member
Interesting thought on the over voltage protection.
On the flip side, I wouldn't want to be stranded somewhere because my DME was slightly over voltage.
I prefer a voltage meter in the car, and the ability to decide how to deal with the issue.
Perhaps a voltage regulator circuit at the DME, so that if the source voltage exceeded the allowable level, it would be brought into check by the secondary regulator.
Then you could get home and deal with it in due course.
On the flip side, I wouldn't want to be stranded somewhere because my DME was slightly over voltage.
I prefer a voltage meter in the car, and the ability to decide how to deal with the issue.
Perhaps a voltage regulator circuit at the DME, so that if the source voltage exceeded the allowable level, it would be brought into check by the secondary regulator.
Then you could get home and deal with it in due course.
06-11-2010, 10:03 PM
#22
Instructor
Thread Starter
Join Date: May 2009
Location: By the Bay, Maryland
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
Replaced the voltage regulator and it seems to be working. I have to run it a few more times to be sure but so far so good. It wasnt to hard to change out the VR.
