View Single Post
Old 09-06-2008, 12:50 PM
EricSilver's Avatar
EricSilver EricSilver is offline
Registered User
Join Date: Mar 2000
Location: Fairfax, VA
Posts: 1,266
Originally Posted by M.B.DOC View Post
Can also be an over-charging OR under-voltage problem. You might watch the system battery voltage as the problem happens.
Would a wet coolant level sensor plug cause a short/ground that would drain the battery enough to cause said low voltage condition?

Three weeks ago I replaced a failed coolant level sensor. In addition to the disappearance of one of the float magnets, I saw that the sensor o-ring had failed, and coolant seeped into the plug, making it visibly wet. Since replacing the sensor, I have not experienced an ASR/limp-home fault under the three conditions that typically cause(d) it:

1.) Car sitting more than 24 hours without being driven.

2.) Significant Variances is ambient temperature and humidity

3.) Sitting overnight after/during a heavy rain.

All of these have occurred since replacing the sensor. Last night, and today, we were/are being hit with hurricane/tropical storm Hanna. I just knew I would see the ASR light this morning when I drove the car. But I didnít.

Adding further support to the low voltage theory is that whenever an ASR fault occurred, the same minimal time interval ( approx 8-10 minutes) needed to elapse before the car could be restarted without re-triggering the fault. I initially thought that some component needed to warm up or dry out, but because the time interval was the same whether it was 90 degrees or 20 degrees, wet or dry, the warm-up/dry out hypothesis did not fly. The time interval was also the same whether the car was moving or idling. The only thing that seems to fit those facts is the battery needing time to build charge to a level that would not trigger the ASR fault.

I am not yet convinced I am out of the woods. I will reserve judgment until tomorrow, when we dry out and have another big change in humidity; and until next week or the week after, when we have the first very big variation in overnight temperatures. But for right now, this is very encouraging.
2008 E350 4matic / Black/Anthracite

Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
Reply With Quote