M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Electrical => Topic started by: B318M42W on March 06, 2009, 10:34:26 PM
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hi everyone!
here's the situation... i don't know exactly whats going on with my car but here's what i found out... i only seem to have about 5V to all my circuits and can't figure out why. I bench tested the main relay and it is good. Radio works about 1/2 the time and no lights come on (except for the interior lights) also, i managed to get everything back no "normal" but that didn't last long until i tried to start the engine. It was a sudden and complete blackout and i'm back to where i'm now. does anyone have a idea of why i'm only getting 1/3 of the voltage i should be getting???
(oh and voltage on main relay pins is ok when "off" but as soon as i turn the key 1 position, it drops back to 4-5V :()
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Sounds like a bad earth mate there are a few in the engine bay that can cause this problem
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hope it's only that... thanks!
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(oh and voltage on main relay pins is ok when "off" but as soon as i turn the key 1 position, it drops back to 4-5V :()
That's because you have a big resistance somewhere (see the bad grounds post above).
With the key off, there is no current flow through the bad ground (or whatever it turns out to be) and so there is no voltage drop across it. When you turn the key to "1", there is current flow and a voltage drop of about 7 volts is made across the bad whatever.
I would turn the key to "1" and then start pulling fuses one at a time. From a VERY quick glance at the ETM start with fuses 8, 9, 10 and 12 and the K3 and K4 relays. See if the voltage goes back to normal when you pull any of these. Doing this will help you isolate where the problem is.
Let us know what you find.
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thanks for the methode! only thing is that i just solved it :D
I got tired of screwing around and whatnot so i decided to start and unscrew things... I isolated about every bunch of wires, took out the instrument cluster, unhooked grounds G300 and G104, both battery poles, ABS computer, ECU, clock, about avery connector under the dash and removed all fuses/relays and also unplugged C101. I looked if any wires grounded themselves where they arn't supposed to, and then i found that all fuses that are hot at all times were related to the ground through i'm not too sure what engine accessory. so I unhooked the battery junction block, and then cleaned the contacts. put it all back together... and she started up ljust fine. however, there were still some issues. here they are:
-horn didn't work, but it tripped some light indications on the dash,
-high beam and low beams didn't work
-fog lights didn't work
- front flashers were weak, and didn,t work on "run"
-hazard worked on accy but not on run
- flasher didn't work on "run"
and yeah... i think that about it...
turned out that i didn't put the ground G104 back on properly so it caused all those weird issues. just made sure it was tight and good contact and it all fixed it.
so basicly, not too sure that fixed the initial problem, if it was
a) the fact of taking everything appart and then putting all back together (making proper connections)
or
b) cleaning of the battery junction block
either way, it worked :D oh and i'd like to say a huge THANK YOU to ak96ss ! the manuel you posted in the referance section was my bible (for 3 days...)