CD Player/Headunit no longer powers up!!!

[Wiker Man]

My Sony CD player head unit has stopped powering up. I have tested the player on a  ac power 12v atx supply and it worked (Red + yellow wire is positive and black is ground). So the head unit itself is good, however something is wrong in the car connections.  I checked the fuses inside the engine bay they were okay except fuse 26 (10a which I replaced).

I thought its a power issue so I used my multimeter and measured the yellow, red and black connectors and sure enough there was no 12V power going to the cd head unit. I checked radio fuse 9 and 44 and both are good. 

Can you guys with the audio/electrical department of these cars or faced such issues please help me through what should i be looking to troubleshoot powering the head unit in the car?   I am a car audio and electrical newbie but have a multimeter too if it helps. I am not looking to take apart my entire dash board apart, again! Are there any hidden fuses? or something?  Recently I have been having some electrical issues with my car after taking it out of the garage after some time(a year or more) At first the alarm started to act up and would refuse to disarm itself after 30 mins had passed and then I noticed the heater pumps only hot air (no cool ac) and then noticed the CD player didn't work.   

[DesktopDave]

I'd start with testing the battery. A healthy battery should have a resting voltage well over 12VDC, measured between the + & - terminals. If you get a low reading, haul it out to a few auto parts stores for a load test. That's the best way to determine how healthy the battery is.

If the battery is strong, I'd double-check the fuse box for loose terminals. The springs are very high quality, but over the years they can loosen up and cause all sorts of electrical maladies. Loose fuses will generate high resistance and heat, enough to deform the fuse or even the fuse box itself.

A lot of aftermarket stereos will have an inline fuse on the unswitched (battery) power leads instead of in the head unit itself. I've noted that those fuse housings can fail as well as the fuses. Fuses can also look good, but be broken internally. Have you checked the radio harness for one? Some splices can also fail, especially those cap crimps and Scotch-Lock connectors that stereo installers prefer to use.

[Wiker Man]

The battery is good, its the connection, it has no power, i checked the fuses, replaced them and I saw there is 12V at fuse 9 and fuse 44. however there seems to be no power at the white/violet wire in the dash.


man I  hate working on these e36 cars, people dont maintain them and they have way too many electrical problems. I just didn't want to take it to a mechanic and drop hm 500 bucks to find out it was a stupid wire or fuse somewhere.  but looks like thats just what i gotta do.

[DesktopDave]

Did you check fuse 28? According to the ETM, that's where the WH/VI wire draws power.

IMHO one of the reasons BMW is such an awesome company is their documentation. If you don't have an ETM, find the one for your E36 here, and download it.

I like to think of wiring as plumbing. A DMM is easy to use once you learn three basic functions (volts DC, resistance, continuity), and wiring in cars is usually pretty simple. I've come to prefer wiring problems to mechanical ones, LOL. Best of all, your friends will start to think you're a genius. I know that there are some logic wires in the E36, but the basic stuff will still get you a long way. Even cheap DMMs are surprisingly powerful. Come to think of it...I haven't even bothered with the logic functions on mine yet. Bet I could fix a lot of newer BMW junk that way!

Knowing how to use a DMM will save you a small fortune with these cars. I have lost track of how many cars I've towed to my house not running - it's a running joke with my wife. All of them had simple electrical problems. All of the previous owners had also "thrown in the towel." Their loss, my gain!
'91 318i - dirty crank position sensor
'82 633CSi - bad position sensor, bad fuel pump relay, lift pump plug, battery positive post was a mess, injectors needed overhauled
'84 745i - bad fuel pump relay

Moral of the story? It's frustrating to track down an electrical fault, but it's cheap! A really good DMM is about $50 these days. I'm considering an '82 Euro 735i 5-speed now...betcha it'll have lots of electrical problems! Even better, the nightmare vacuum servo HVAC will need overhauled. No way anyone else will be touching that car; bringing old iron like that back to life is tremendously rewarding.

You know what I used to do for motivation? I'd get a few hundred in cash out of my bank account and put it on the dashboard while I worked. It's incredibly motivating to see what you're earning instead of paying out. A penny saved...

[Wiker Man]

Hey thanks for getting back to me. you know I often have these kind of frustrations with electrinics before I make a break through. I was also having problems with my alarm which would stop disarming the car after a few hours had passed. I think I have managed to reset now (fingers crossed).

Sorry for being down then, I got frustrated since I am shifting places and cant find enought time to sit down and look at it myself. but thats what I am going to do next week. Hopefully. I have a multimeter.

if you know other members good with cd players and stuff ask them to chip in too please.
I will see what I can do and come back here when I am ready, in a few more days. 

Thanks

[Wiker Man]

hey dave, I figured it out!! it was a small connector just under the passenger footwell. it has a red wire with a white stripe which I think provides the 12V power to the CD Player Slash Headunit. It has a 1 foot by 1 foot plastic box with some other connectors left inside. So when I did the interior of my car I must have forgot about reconnecting. now that I have reconnected it the power is restored back to my head unit. I also think it may have caused issues with my alarm which I will rewire up tomorrow and look.

thanks for your suggesting and urging me to look in there even for one last time

[DesktopDave]

Always good to hear about a solution. I prefer mechanical problems to electrical troubleshooting, but you can't argue with a "free" fix.

I'd rather spend time than money, that's for sure!