92 E36 Window Mystery

[andyleonard]

All 4 electric windows and sunroof work fine...*unless* the outside temp is @ 100*...in which case - nothing. The whole windows/sunroof circuit is dead. After the car cools down, all is good. Finally the other day the circuit breaker in the dash exploded and I bypassed it with a 20A fuse and windows/roof have been just fine regardless of temp. I was sure I had it licked until today.

It did it again, shut everything off when hot, but didn't self-correct when the car cooled down. I pulled over, changed the fuse, nothing. Finally, after furiously pushing all the window buttons and changing the fuse and jumping the circuit breaker with a paperclip and wiggling the ignition key, etc., I reinstalled the original fuse, pushed the window switch one last time...and the fuse blew.

I replaced the fuse with a new one and...everything works.

What's happening? Is the heat sticking a relay or a motor? Help.

[shogun]

you probably have an overload in the system, clean all window lifter rails, remove old hardened grease etc, maybe it is similar to E34 and E32, short description of the system:

here is a German language detailed description of the ZKE central chassis electronics for E34 and E32, I assume on the E36 it is similar http://www.e32-schrauber.de/bmw/s-zke.htm
section 11 has the function diagram of electric windows and electric sunroof.
there is a internal reversible fuse inside the GM general modules for this.
The relay switches off
-if there is longer than 60 seconds a current of about 36A or
- if longer than 0.3 seconds a current between 36 and 60A, or (overloading)
-if longer than 0.1 seconds, a current greater than 60A flows (short circuit)

To protect the load circuits, TSH / ZV /ZS / FH / SHD from overload, there was installed in addition to that an electronic fuse 30A (reversible). In the GM the voltage drop is measured at the RM = relay module, and depending on the voltage drop (current threshold) interrupts the safety relay is the load current.

The switch off values of the 30A fuse will not be reached here (it would just melt when there is a defect in the electronic security). The threshold of this electronic fuse is positioned so that is always switches off automatically before overload of the connected controllers. An automatic restart is only possible after 60 seconds!! But only if these consumers were turned off, or there is no short circuit. Automatic resetting can be made 6 times when terminal 15 is switched on. This lock is released again by switching off the terminal 15.

Silicon spray the rubber parts of the windows so that there is not so much friction between the glass and the seals. Also the guide rails inside the door.

TSH = Tuerschlossheizung = door lock heating
ZV/ZS = ZentralVerriegelung mit ZentralSicherung = central locking with central dead locking
FH = FensterHeber = door lift
SHD = StahlHebeDach = steel slide/lTilt sunroof

[andyleonard]

How would the heat affect the overload and why would the system shut down with NO buttons being pushed?

[shogun]

just a guess: with heat material expands and that can could more friction + overload. Or what you assume:
Is the heat sticking a relay or a motor?

Do not by-pass a circuit breaker or use a bigger fuse, might be dangerous.

[dworthy]

Do not by-pass a circuit breaker or use a bigger fuse, might be dangerous.

^^ FACT! Every wire can handle a specific amount of current, once it get overloaded, they melt/burn. When the car is engineered, they always will have a safety factor in there of a couple of amps below the max, so if it's a 7.5 amp fuse, normally the circuit can handle 8 - 9 amps before catastrophic failure.

With any fuse, it can age and get weak. Like noted above, clean the rails out and put fresh grease back in. After 30 years I am sure it's tired and needs a bit of help going up/down. The white plastic slider can be replaced as they too get worn, and can cause binding. If the GM-3 senses over-voltage, it will think the motor is binding against something and not work, part of the Anti-Trap built into the car.

[shogun]

CENTRAL BODY ELECTRONICS (ZKE IV) , Models: E36 and Z3, Production Date: E36 1994 MY (including 318ti) to End of Production Z3 Coupe, http://www.mdv.se/bmw/bmw%20sheets/3%20ZKE%204%2004-26-01.pdf
Power Windows/Sunroof
Purpose of the System
The features of the power windows and sunroof system include:
• One-touch operation in both directions (up/down) on the front windows, down only on the rear windows.
• Anti-trap detection is on the front windows only (initialization required for one touch operation).
• The control of the rear windows is carried out through a Relay Module (RM IV).
• The switches in the center console controls all four windows and the rear window lock out feature.
Principle of Operation
All window operation request signals are digital inputs to the GM.
• Comfort Closing of the windows from the driver’s or passenger’s lock cylinder when held in the locking position.
• When the ignition key is in accessory or “ON” press the switch to open or close the windows. Window operation is possible with the ignition switched off until a front door is opened or 16 minutes (maximum) has elapsed.
• Power protection against a jammed or seized motor is monitored by the hall sensors in the window motors. The GM will interrupt the power to a jammed motor. Rear windows utilize current sensing for shut off.

The one-touch function is activated by momentarily pressing the window switch to the second detent. Window travel will cease when the full up or down position has been reached. One-touch can be canceled by pressing the window switch a second time. Antitrap is provided by the GM monitoring the door glass movement from the hall sensor. If the door glass encounters resistance in the closing direction (>100Nm) the motor will stop and reverse direction for 50 mm of travel.

Window Operation specific to the E36 Convertible:
• Central Window Switch: Located in the center console, the switch will raise or lower all four windows at the same time. The window lowering has the one-touch feature.
• Convertible top operation: Prior to lowering the top, the top control module signals the GM to lower all four windows half way.
- If the top switch is held after the top is fully lowered, the windows will close fully.
- If the top switch is held after the top is fully closed the GM will close the windows.
• With the introduction of the fully automatic convertible top, the comfort close feature of the convertible was also added.

Window Operation specific to the Coupe, Convertible and Z3 Coupe:
The design of the E36 Coupe, Convertible and Z3 Coupe required changes in the window operation.
• When opening the door, the door glass is automatically lowered by approximately 10mm. When the door latch opens (switch closes), the window will drop. It remains down until the door contact switch opens when the door is closed. The window will then raise back into the door seal.
• When the door is closed, the glass is raised back into the seal. This allows the glass to drop out of the door seal when opening the door and provides a tighter seal when the door and glass are closed.
• The window motor contains a Hall sensor for this feature that is monitored by the GM.

[andyleonard]

FWIW this is an early 92 and doesn't seem to have the "one-touch" stuff. What's confusing me about the concept of a "stuck motor" is that it makes no difference which window or SR button I touch, there's NOTHING. Then when the temp comes down it's all good. I'm suspecting a cold solder joint in a module or relay somewhere.

But where?

[shogun]

yes, could be a solder joint in a module or relay. Try to check systematically which items are suspects, must be something "central" which receives/sends a signal to all windows, here are the wiring diagrams by built year
http://wedophones.com/BMWManualsLead.htm
maybe someone had a similar problem and can chime in with some hints

[andyleonard]

This being an early car, it seems the "Comfort Relay" under the dash is the place to look if seats and sunroof work...but no windows, sometimes. I'm betting on a cold solder joint. Will report back.

[andyleonard]

Yup. Cold solder joints in "Comfort Relay" under left side dash behind impact plate. Not only do the windows/roof now always work regardless of temp, but "one touch" feature has also reappeared after 10 years.