Odd Electrical Issue, w/ Video.

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Odd Electrical Issue, w/ Video.

Postby Nsquared97 » Wed Feb 27, 2013 6:24 am

So I tried to start my car to get to work today ('87 325is, M20B25, 5spd etc.) and it acted as if the battery was completely dead. Didn't even attempt to crank, no lights on the dash at all, etc. Took my buddies car to work, just got home and tried it again, here is what it's doing when I turn the ignition to run:

I put a battery changer on the battery, but with a DMM I am reading 12.3-12.5V across the battery, so I don't think that's the issue, and it was new less than a year and a half ago.

Only electrical issue I can think of lately is over the last two days the engine oil idiot light (not the check light, the one in the cluster) would flicker occasionally when I let off the gas to slow down for a stop light. Other than that the car has been running just fine.

I am guessing maybe a relay or something, I am going to start looking through wiring diagrams and see if I can figure anything out. Any help is greatly appreciated.
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Re: Odd Electrical Issue, w/ Video.

Postby Yoshi » Wed Feb 27, 2013 12:40 pm

Try a different battery. Maybe a dead cell? That's very odd...

check voltage at the junction area at the front of the car passenger's side.
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Re: Odd Electrical Issue, w/ Video.

Postby M20_fever » Wed Feb 27, 2013 2:06 pm

did you check the main ground connection? Tried starting it on a jump pack it jump starting it?
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Re: Odd Electrical Issue, w/ Video.

Postby Yoshi » Wed Feb 27, 2013 3:16 pm

yea could be that. odd that it would suddenly shit itself though. Essentially, you put the key to on, the power runs through the car until it's saturated in the engine and can't ground through the chassis to the ground. After a while, the electricity dissipates and you can do it again a few hours later.
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Re: Odd Electrical Issue, w/ Video.

Postby AustinR » Thu Feb 28, 2013 1:47 am

Now that is weird.

What's up with you tach jumping up to 2000 rpm at the end of the video? Probably just start by checking your ground connections like Tony said although I'm sure you've already done that.
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Re: Odd Electrical Issue, w/ Video.

Postby Nsquared97 » Thu Feb 28, 2013 5:50 am

Haven't really had much time to try stuff out, but here's an update from today. Jumped the car this morning, she fired right up. Let it sit for a bit to warm up, then took it out to try and charge up the battery some. My plan was to drive enough for the alternator to charge the battery, then let the car sit while I was at work (didn't trust it enough to take it to work, didn't want to be stranded there when I got out). The car ran like absolute crap. Up to ~2500rpm was Ok, then it would buck/sputter/kick like crazy. Took this video when I got back home, just reving the car in neutral, but it behaved very similar driving with the engine under load as well.

Also, what is that green light for that's lit up? Has arrows facing left/right? I have seen it come on at random times before, but very brief and very sporadic. Not sure if that has anything to do with this or not, but it was on the whole time I had the car running.

So, once I got home from work tonight I checked the voltage at the battery again, 12.5V. Tried to start the car, turned the key to run and everything lit up like normal, tried to start and just got a click. After that all the lights died like they did in the original video.

I haven't had a chance to try the tests you guys mentioned, I am going to attempt those in the morning. Unfortunately I don't have a helper so watching the voltage while cranking could prove to be tricky. I'll see what I can figure out tomorrow.
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Re: Odd Electrical Issue, w/ Video.

Postby Nsquared97 » Thu Feb 28, 2013 5:51 am

AustinR wrote:What's up with you tach jumping up to 2000 rpm at the end of the video?


You know my tach is posessed, and it makes you laugh.
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Re: Odd Electrical Issue, w/ Video.

Postby Yoshi » Thu Feb 28, 2013 12:24 pm

heh, you know what? It's a dead battery or a battery that isn't charging. Take the batt lead off while the car is running, see if it still runs. also double check the ground wire on the engine for giggles. I like to run a secondary one from the passenger's side of the AC to the frame.
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Re: Odd Electrical Issue, w/ Video.

Postby M20_fever » Thu Feb 28, 2013 2:32 pm

Yeah, dead battery is my guess. Have you swapped your cluster for a euro version? That green <==> light seems to be a big mystery on all the forums. Pretty interesting it's not in the manual and nobody knows what's it's for. Others who have said it came on were usually experiencing poor running when it was illuminated. Now I'm very curious to know what it's for.
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Re: Odd Electrical Issue, w/ Video.

Postby Nsquared97 » Thu Feb 28, 2013 6:34 pm

M20_fever wrote:Have you swapped your cluster for a euro version? That green <==> light seems to be a big mystery on all the forums. Pretty interesting it's not in the manual and nobody knows what's it's for. Others who have said it came on were usually experiencing poor running when it was illuminated. Now I'm very curious to know what it's for.

Nope, cluster was out of my '87 IC parts car. Just your standard 'I' cluster, nothing special there. If it is a dead battery, I am glad I got the 2 year warranty for it, now to find that receipt...

Yoshi wrote:heh, you know what? It's a dead battery or a battery that isn't charging. Take the batt lead off while the car is running, see if it still runs. also double check the ground wire on the engine for giggles. I like to run a secondary one from the passenger's side of the AC to the frame.

Going to check the grounds right now. If I take that lead off while the car is running, and it keeps running, that would indicate the battery is dead (thus not doing anything) correct?
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Re: Odd Electrical Issue, w/ Video.

Postby Yoshi » Thu Feb 28, 2013 10:52 pm

Nsquared97 wrote:Going to check the grounds right now. If I take that lead off while the car is running, and it keeps running, that would indicate the battery is dead (thus not doing anything) correct?



Yep
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Re: Odd Electrical Issue, w/ Video.

Postby M20_fever » Fri Mar 01, 2013 2:16 am

wait, what? Pulling the battery while its running would test the alternator, not the battery. Car should run off the alternator once its started, not the battery.
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Re: Odd Electrical Issue, w/ Video.

Postby Nsquared97 » Fri Mar 01, 2013 5:12 am

M20_fever wrote:wait, what? Pulling the battery while its running would test the alternator, not the battery. Car should run off the alternator once its started, not the battery.


That's kinda what I was thinking. And wouldn't that also just break the circuit everything runs off of?
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Re: Odd Electrical Issue, w/ Video.

Postby Yoshi » Fri Mar 01, 2013 12:08 pm

M20_fever wrote:wait, what? Pulling the battery while its running would test the alternator, not the battery. Car should run off the alternator once its started, not the battery.



Well, if the alt is running the car, then the battery is probably dead. It's not a sure condition I suppose. I guess the only thing you'd know 100% is that the alternator is working. But then, I'd assume the battery is dead
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Re: Odd Electrical Issue, w/ Video.

Postby M20_fever » Fri Mar 01, 2013 1:44 pm

why? A brand new battery will behave the same way as a dead one when the car is running. I guess if you want to test tje battery this way you would need to start the car and unplug the alternator. Car should run for a few minutes before lights and such start dropping out. Easiest way to check is to take the battery to a parts store and get it load tested, or swap in a known good battery and try it.
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