Cold weather electrical problem

[lei2015692]

Hello.

I have a 1995 525i that absolutely refuses to start when the outside temperature goes below 40 degrees. I had run the usual and somewhat extensive trouble shooting scenarios. Then while my son was helping me earlier tonight we put a small forced air room heater in the back seat after reemoving it with the air flow directed at the security system components in the rear floor board and waited approximately 30 minutes, the whaalaa, the car started and ran. My question is: What needs to be replaced to alleviate the problem? I will add that the starter, solenoid, ignition switch, neutral safety switch, and fuel pump have been replaced new along with known good battery along with all relays and fuses in engine compartment have been checked and known good. The problem also effects the door locks when the car will not start, meaning they will not function to lock the door and even the key being inserted has no effect on the issue. When the outside is temperature is 40 degrees and above the car starts and runs fine. The problem only occurs when the temperature goes below 40 degrees. As I stated above when the forced air heater is directed right on the electrical components in the rear seat floor board for approximately 30 minutes it will start like there's no problem. I would really appreciate someone to direct me in the correct direction to take to finally rid this old car of its ailment. Thank you.

[shogun]

welcome here.
You mentioned that the battery has already been changed. But better -and that is the easiest and does not cost anything - make a battery test under load.
Other things to check: corrosion on the contacts. Did you use a good electric contact cleaner for all the relays and cleaned the spades of the relays as well as the fuses?

Another maybe far fetched idea: could your fusable link have a haircrack? When it gets warmer, metal expands, so then the haircrack could be less and all works well, worth to check
BMW E34 Website (http://www.bmwe34.net/E34main/Maintenance/Electrical/Fusible_link.htm)
the fusibale link is always next to the battery, so either in engine room or under rear seat

also check the ground cable connection of the battery.

Hints and Tips (http://www.bba-reman.com/content.aspx?content=hints_and_tips#bmw)

[lei2015692]

I made my best attempt at cleaning all electrical contacts. I should also share that while the door locks don't want to work when the 525 is experiencing the intermittent electrical problem, all other electrical such as headlights, dash lights, radio.....etc.... work fine. I can also jump the solenoid to starter and get engine to turn over, but engine will not start. I have not checked for fire or fuel pump operating while the electrical issue occurs. I'm thinking that since the car starts and runs fine when the outside temperature is warm enough that the car will operate that to chase any of those areas would be futile. Also, with all other electrical operating I'd think the fusible link should be fine. I haven't run a complete check of the system components in the rear floor board yet as it was night time when my son and I discovered the forced air on the system itself would alow the car to start. Oddly enough when I did the heater idea previously it did not work, but I did not have the heated air directed directly on to the system. I didn't think there would be that much of a difference but obviously it did. I will look into the link you sent me and see if I can find something. If you can think of anything else please let me know. I've done quite a bit of "wrenching" over the years, but I'll be damned if I've ever seen such cantankerous ghost in an electrical system before. But as I've read before, "BMW's have a way of defying logic sometimes." LOL

[shogun]

just in case you need:
wiring diagrams, includes component location charts, fuses, relays etc
E34 (1988 to 1995 5 Series) Wiring Diagrams (http://shark.armchair.mb.ca/~dave/BMW/e34/)
shop manuals
BMWTIS -- Repair Information (http://www.bmwtechinfo.com/repair/main/)
parts catalog
Welcome, BMW fans! (http://bmwfans.info/)

[Tiger]

I would day you need to replace all your fusible links and the ground cable.

[genphreak]

Seen this before in a '95.

The wipers didn't work either (except on full speed) and the hazard lights would flash intermittently requiring a battery disconnect to reset.

What solved it for me was a new body electronics loom from firewall to bumper. I never isolated the root cause, but would have loved to. It took me 2 years to eventually do it and a big weekend job (more if you're not well organised) as the seats, and carpets and many more little bits and pieces have to come out. :-(

You are however very lucky- you live somewhere cold enough to test the error... so maybe you can remove modules, heat individual items (RM, GM, DWA, relays, fuses, etc.) and find the actual cause.

Suggest you check for (and verify):

1. All grounds under the back seat inc those in the middle and those in the seat bulkhead in front of the battery.
2. Fusible links (they fail microscopically due to vibration, age heat and electrolysis/oxidation.
3. Is the Power Protection relay triggering? (in the rear power distribution box)
4. Remove the power dist box (3 or 4 10mm plastic nuts). Lift it up- is there water, corrosion under the rear power dist box? 5. Any dampness under the carpets? (stick your hand under to see)
5. Remove the DWA unit and re-older the heavy connections on each of the relays mounted on the PCB. Same with the relay module, the joints are known to fail under heat/age/vibration. The DWA unit is in front of the power distribution bix (hiding between it and the the seat bulkhead)
6. Check the ECU for codes. I don't expect EWS or DWA as this is a malfunction that affects much more than starting. A diagnostics checked can read the codes but doubt it will help you pinpoint anything.

One thing my old loom had was corrosion running down the the wiring from the ends and in the joints. There are several meters of excess wiring under the Left hand rear footwell which all bind together, a lot of grounds and other wires joined at the ends that might just need to be re-soldered...

Do keep us posted on your progress. Others have had this I know but I've never heard how they dealt with it.

[lei2015692]

So I've gotten into the back power distribution and I have a question. Will the general module have intermittent issues or will it just go bad? I'm noticing a lot of clicking coming from it both when the car is started and quite a lot of clicking when the car is shut off and key is out of the ignition. I've also noticed that the battery seems to be discharging as it has never done it before. Or I should hadn't done it before we had a 1 degree night. It will charge and stay charged for hours, then over night it will drain. After charging it will start car with no problem and do so consecutively. I did a charge draw test and it was less than 0.1 and while car is running and charging it is at a nice 14.2. I had bought the battery less than two years ago and it has never given a bit of trouble until this last week after the cold spell. I'll take it and get it checked tomorrow. My reason for mentioning the battery issue was to see if it my correlate with my ongoing issue. I'm also really puzzled with the starting and not starting ghost. It will start and not start at will. Sometimes wiggling a wire will correct it, sometimes a blow dryer on the back side of the general module will allow it to start, and sometimes allowing to do nothing more than sit will allow it to start. I will say that it can start at lower temps than it did before since we've messed with it, but nothing has thouroughly fixed it as of yet. My next step I believe is to take each and every one of the connectors out of the housings and inspect intensely and clean and crimp to see if it takes care of issue. I still need to know more about the durability of the general module.

[shogun]

I assume the clicking comes from the RM = relay module besides the GM. The GM is just the brain, execution is by the RM.


My next step I believe is to take each and every one of the connectors out of the housings and inspect intensely and clean and crimp to see if it takes care of issue
good idea.

Of course, the GM can also break like any other electronic part, same like the RM.
But I never had a problem with them since about 20 years on my car, but others had.
http://www.bimmernut.com/forum/5-series-bmw/43782-general-module-problem.html

[genphreak]

Try to use something as good as DeoxIT (http://www.caig.com/), and post close ups before you do of the connectors that plug into the RM and GM through the bottom of the power distribution box. You can pull the insulation back on any wires that are oxidised with your finger nails to assess the wire oxidation.

One notices the clicking form the RM when the seat is out as it shuts it up completely once its in place. If the clicking is the shut down sequences (after the ignition switch is returned to position 0, these will mostly go away after 30s or so, esp. if you lock the doors. (leaving the windows down to listen will not affect the way the vehicle's circuits shut down). This is normal.

If the clicking is constant during engine run or ignition on (and is not the indicator, wiper relay, alarm siren driver, etc.) you have a problem. Maybe some wire or connector's resistance has gone high on a relay feeder circuit or ground, or maybe there is a hairline crack inside some relay's PCB mounting (solderjoint).

[lei2015692]

I want to thank everyone for helping me with this issue. I had my son go through the electrical connections. That didn't fix the issue, but it did need to be done as proper troubleshooting. The fix finally got zeroed down to the general module box. We ordered one off of Ebay for $34.99 USD and as sure as the sun shines the car will start no matter how cold it gets. I'd also like to mention that the excessive clicking is over with. I still have an issue with my remote keyless entry giving me fits. I'm thinking a fresh reprogramming from the remote chip may take of that. If it does I willl also post the outcome. I hope if anyone else having the same issue I had, sees this and it helps to quicken and cheapen the fix for them. Thanks again guys for all your help. PEACE!

[Russell]

Seen this before in a '95.

The wipers didn't work either (except on full speed) and the hazard lights would flash intermittently requiring a battery disconnect to reset.

What solved it for me was a new body electronics loom from firewall to bumper. I never isolated the root cause, but would have loved to. It took me 2 years to eventually do it and a big weekend job (more if you're not well organised) as the seats, and carpets and many more little bits and pieces have to come out. :-(

You are however very lucky- you live somewhere cold enough to test the error... so maybe you can remove modules, heat individual items (RM, GM, DWA, relays, fuses, etc.) and find the actual cause.

Suggest you check for (and verify):

1. All grounds under the back seat inc those in the middle and those in the seat bulkhead in front of the battery.
2. Fusible links (they fail microscopically due to vibration, age heat and electrolysis/oxidation.
3. Is the Power Protection relay triggering? (in the rear power distribution box)
4. Remove the power dist box (3 or 4 10mm plastic nuts). Lift it up- is there water, corrosion under the rear power dist box? 5. Any dampness under the carpets? (stick your hand under to see)
5. Remove the DWA unit and re-older the heavy connections on each of the relays mounted on the PCB. Same with the relay module, the joints are known to fail under heat/age/vibration. The DWA unit is in front of the power distribution bix (hiding between it and the the seat bulkhead)
6. Check the ECU for codes. I don't expect EWS or DWA as this is a malfunction that affects much more than starting. A diagnostics checked can read the codes but doubt it will help you pinpoint anything.

One thing my old loom had was corrosion running down the the wiring from the ends and in the joints. There are several meters of excess wiring under the Left hand rear footwell which all bind together, a lot of grounds and other wires joined at the ends that might just need to be re-soldered...

Do keep us posted on your progress. Others have had this I know but I've never heard how they dealt with it.
sounds like a real mess, Was your car exposed to extremme weather conditions at some point in it's life?

[Russell]

I want to thank everyone for helping me with this issue. I had my son go through the electrical connections. That didn't fix the issue, but it did need to be done as proper troubleshooting. The fix finally got zeroed down to the general module box. We ordered one off of Ebay for $34.99 USD and as sure as the sun shines the car will start no matter how cold it gets. I'd also like to mention that the excessive clicking is over with. I still have an issue with my remote keyless entry giving me fits. I'm thinking a fresh reprogramming from the remote chip may take of that. If it does I willl also post the outcome. I hope if anyone else having the same issue I had, sees this and it helps to quicken and cheapen the fix for them. Thanks again guys for all your help. PEACE!

Thank you for all your efforts. Electrical issues are one of our main concerns as there cars get older.

[lei2015692]

Russell, the old Bimmer was a Phoenix car. It had most definitely seen the extremes of heat. I guess when it came into the cold weather of Missouri it just didn't like it. I hope this fixes it for a while and it can get the use out of it I'm sure that's left in it. It hasn't hit 200,000 miles yet.......just now gettin broken in......lol