Rear window defroster/1989 930
11-28-2003, 01:38 PM
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Rear window defroster/1989 930
Hi whizz kids,
This may sound a bit "basic", but I don't know the answer, though I am sure there are a few of you out there that do!
Car is a 1989 930 (one of the last). Problem is that the top and bottom portions of the rear window defroster are not heating up. The middle portion is OK.
The window appears to be divided into 3 heating areas, noticeable by a seperation in the elements along one side of the window into 3 (one continuous element on the other side). I presume that the electrical connection to the heating elements is to the center section, and concealed behind the seal, as I cannot see it.
Fuse is OK (looks OK, and other systems on the same circuit work fine).
Any input appreciated.
Regards,
Keith
This may sound a bit "basic", but I don't know the answer, though I am sure there are a few of you out there that do!
Car is a 1989 930 (one of the last). Problem is that the top and bottom portions of the rear window defroster are not heating up. The middle portion is OK.
The window appears to be divided into 3 heating areas, noticeable by a seperation in the elements along one side of the window into 3 (one continuous element on the other side). I presume that the electrical connection to the heating elements is to the center section, and concealed behind the seal, as I cannot see it.
Fuse is OK (looks OK, and other systems on the same circuit work fine).
Any input appreciated.
Regards,
Keith
11-29-2003, 01:05 AM
#2
Instructor
YIMEX,
Interesting!
I have a similar problem with the CENTER section (more or less) of the rear window on my 1986 U.S. spec Carrera 3.2. It's a real pain as that's where the interior rearview mirror has its primary view. It might also be important to note that my rear window has 19 heating elements that appear to be orange in color when viewed from the outside of the vehicle (sorry, didn't want to go into TOO much detail but sometimes... ;-) ).
I just went out to the garage and poked underneath the exterior rubber seal on the rear window. I couldn't spend too much time as dinner was getting ready but it does seem (as you mentioned) that a constant connection strip (power or ground I know not) ran down the right (passenger) side of the window.
A quick check of the left (driver) side of the window (again, under the exterior seal) found a definite and 'as designed' break in the window's internal heating element circuitry.
I'll check this out further tomorrow under better lighting and let you know what I find. I've got electrical schematics and will bone up on them.
At this point I'd say that you (and I) do not have a fuse issue. If ANY of the elements heat (19 total with 4~5 not working in my case), you've got power and appropriate ground from the car's electrical distribution system.
When I noticed my problem, my initial thought was that vibration or corrosion from water seepage had done me in on the inop segments and that the only fix was (take cover) a new rear window, but let me check on how this thing is supposed to work and I'll get back.
A new rear window w/heating elements may be the only real solution but there is much to be said for researching the issue and thinking good thoughts!
In the meantime, could you tell us how many heating strips (individual wire elements) your rear window has, what side of the window has the 'continuous' connection, what side of the window has the 'segmented' connections and how the segments are grouped with respect to the individual wire heating elements they connect to?
I'll know the answers to these questions tomorrow for MY car and I'd be surprised if we're different but you never can tell! Look for my next post.
Barry
Interesting!
I have a similar problem with the CENTER section (more or less) of the rear window on my 1986 U.S. spec Carrera 3.2. It's a real pain as that's where the interior rearview mirror has its primary view. It might also be important to note that my rear window has 19 heating elements that appear to be orange in color when viewed from the outside of the vehicle (sorry, didn't want to go into TOO much detail but sometimes... ;-) ).
I just went out to the garage and poked underneath the exterior rubber seal on the rear window. I couldn't spend too much time as dinner was getting ready but it does seem (as you mentioned) that a constant connection strip (power or ground I know not) ran down the right (passenger) side of the window.
A quick check of the left (driver) side of the window (again, under the exterior seal) found a definite and 'as designed' break in the window's internal heating element circuitry.
I'll check this out further tomorrow under better lighting and let you know what I find. I've got electrical schematics and will bone up on them.
At this point I'd say that you (and I) do not have a fuse issue. If ANY of the elements heat (19 total with 4~5 not working in my case), you've got power and appropriate ground from the car's electrical distribution system.
When I noticed my problem, my initial thought was that vibration or corrosion from water seepage had done me in on the inop segments and that the only fix was (take cover) a new rear window, but let me check on how this thing is supposed to work and I'll get back.
A new rear window w/heating elements may be the only real solution but there is much to be said for researching the issue and thinking good thoughts!
In the meantime, could you tell us how many heating strips (individual wire elements) your rear window has, what side of the window has the 'continuous' connection, what side of the window has the 'segmented' connections and how the segments are grouped with respect to the individual wire heating elements they connect to?
I'll know the answers to these questions tomorrow for MY car and I'd be surprised if we're different but you never can tell! Look for my next post.
Barry
11-29-2003, 08:14 AM
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Hi Barry,
Thanks for your input. Appreciate the detail (impossible to trouble-shoot otherwise).
My car is a European spec 1989 930 (one of the last). The rear defroster has 19 orange elements, split into 3, 9 and 5, from top-to-bottom. The LHS (passenger) side (vertical) element is divided into 3 sections, while the RHS (vertical) is continuous. The middle (9) work normally, but neither of the others seem to.
I would be very interested to hear what you find out, particularly as you have the wiring diagrams. I cannot help wondering if there is some form of built-in load-shedding, but that would seem pretty sophisticated for a car!
Regards,
Keith
Thanks for your input. Appreciate the detail (impossible to trouble-shoot otherwise).
My car is a European spec 1989 930 (one of the last). The rear defroster has 19 orange elements, split into 3, 9 and 5, from top-to-bottom. The LHS (passenger) side (vertical) element is divided into 3 sections, while the RHS (vertical) is continuous. The middle (9) work normally, but neither of the others seem to.
I would be very interested to hear what you find out, particularly as you have the wiring diagrams. I cannot help wondering if there is some form of built-in load-shedding, but that would seem pretty sophisticated for a car!
Regards,
Keith
11-30-2003, 10:46 PM
#4
Instructor
YIMEX,
The schematic's I have (Bentley's) indeed show some interesting stuff!
First, it shows that the Rear Window Defogger (1986-1989) heater elements embedded in the glass are indeed divided into three segments (as we have found), although it doesn't show how many elements are connected to each segment - no worry as I think we can see this easily by gently poking under the seal to see what elements run where (again, as both of us have done and our info matches - except for you having to drive on the wrong side of the car ;-) ).
Second, the schematic shows that two of the segments share a common power source and ground. The third has it's own power source and ground.
There is also (apparently) a relay in the engine compartment that controls power distribution to the two positive feeds mentioned above.
YOU have TWO segments inop and I have only ONE and this is interesting to say the least! The problem with the schematic is that it's not clear in its layout as to what segments would be identified as TOP, CENTER and BOTTOM. Oh well, we'll find out...
Step one is to check the two power sources coming from the engine compartment relay to make sure the relay is working correctly and providing power to the heater elements.
Step two is to find the actual connections to the heater elements in the window. According to the schematic we're looking for two primary power connections (as sourced by the relay) and two ground connections PLUS one cascading power connection and one cascading ground connection for the two segments that are inter-connected.
The latter, 'cascading', connections might be incorporated in the glass itself but the schematic shows connection points that would be typical of a blade type connector and I hope that's the case!
All of this, unfortunately, takes time to research and I'll probably not be able to get back on this for a week or two due to the holidays but keep the faith!
One other thing on this. I have a 'black box' attached to the upper right interior portion of the rear window via a white adhesive pad. Some sort of printed circuit (PC) board w/solder is visible around and underneath the pad. It has a 'coax' type cable connection running to it and I always thought that this had something to do with the rear window defogger but I don't see it on the schematic and (from the outside of the car) don't see any 'real' connection from it to the window heating elements.
What is this? Is it factory theft-alarm related (rear window breakage?) or am I being tracked by Aliens?!?!? ;-)
Barry
The schematic's I have (Bentley's) indeed show some interesting stuff!
First, it shows that the Rear Window Defogger (1986-1989) heater elements embedded in the glass are indeed divided into three segments (as we have found), although it doesn't show how many elements are connected to each segment - no worry as I think we can see this easily by gently poking under the seal to see what elements run where (again, as both of us have done and our info matches - except for you having to drive on the wrong side of the car ;-) ).
Second, the schematic shows that two of the segments share a common power source and ground. The third has it's own power source and ground.
There is also (apparently) a relay in the engine compartment that controls power distribution to the two positive feeds mentioned above.
YOU have TWO segments inop and I have only ONE and this is interesting to say the least! The problem with the schematic is that it's not clear in its layout as to what segments would be identified as TOP, CENTER and BOTTOM. Oh well, we'll find out...
Step one is to check the two power sources coming from the engine compartment relay to make sure the relay is working correctly and providing power to the heater elements.
Step two is to find the actual connections to the heater elements in the window. According to the schematic we're looking for two primary power connections (as sourced by the relay) and two ground connections PLUS one cascading power connection and one cascading ground connection for the two segments that are inter-connected.
The latter, 'cascading', connections might be incorporated in the glass itself but the schematic shows connection points that would be typical of a blade type connector and I hope that's the case!
All of this, unfortunately, takes time to research and I'll probably not be able to get back on this for a week or two due to the holidays but keep the faith!
One other thing on this. I have a 'black box' attached to the upper right interior portion of the rear window via a white adhesive pad. Some sort of printed circuit (PC) board w/solder is visible around and underneath the pad. It has a 'coax' type cable connection running to it and I always thought that this had something to do with the rear window defogger but I don't see it on the schematic and (from the outside of the car) don't see any 'real' connection from it to the window heating elements.
What is this? Is it factory theft-alarm related (rear window breakage?) or am I being tracked by Aliens?!?!? ;-)
Barry
12-02-2003, 12:13 PM
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Hi Barry,
I have been checking with a couple of other sources (911 specialists), and they confirm all the info in your message.
Apparently, the most likely culprit is the relay, which sits on the LHS wall of the engine compartment (it is the forward-most of 3, along with 3 fuses, in the 930, behind a plastic cap. The non-turbo models probably have 2 relays, as the centre one is for the air metering valve and intercooler). The said relay also acts as a power distributor, with (as you say) two separate sources, one powering the centre section, and the other the other (upper and lower) two sections of the demister.
Playing with the relay and lubricating the contacts (needs a 10mm socket to remove) has cured the problem with my car, at least temporarily. The relay will probably need to be replaced at some point.
Is the "black box" stuck to the inside of your rear-screen not a GPS antenna (these "see" through the glass, and do have a co-ax type cable)?
Regards,
Keith
I have been checking with a couple of other sources (911 specialists), and they confirm all the info in your message.
Apparently, the most likely culprit is the relay, which sits on the LHS wall of the engine compartment (it is the forward-most of 3, along with 3 fuses, in the 930, behind a plastic cap. The non-turbo models probably have 2 relays, as the centre one is for the air metering valve and intercooler). The said relay also acts as a power distributor, with (as you say) two separate sources, one powering the centre section, and the other the other (upper and lower) two sections of the demister.
Playing with the relay and lubricating the contacts (needs a 10mm socket to remove) has cured the problem with my car, at least temporarily. The relay will probably need to be replaced at some point.
Is the "black box" stuck to the inside of your rear-screen not a GPS antenna (these "see" through the glass, and do have a co-ax type cable)?
Regards,
Keith
03-01-2004, 05:01 AM
#7
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Keith,
I have read all this and it appears I have exactly the same problem as you. I read that you just messed with the relay and that cured the problem for now. I do not really know how to mess with relays! I'm going to buy one, but is this definately the reason? Did you end up buying a new one anyway? How can a faulty relay just make the middle section demist?
Cheers,
Justin
I have read all this and it appears I have exactly the same problem as you. I read that you just messed with the relay and that cured the problem for now. I do not really know how to mess with relays! I'm going to buy one, but is this definately the reason? Did you end up buying a new one anyway? How can a faulty relay just make the middle section demist?
Cheers,
Justin
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03-01-2004, 12:42 PM
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I know on my '76, targa, there is a 2 stage rear defrost. Not sure exactly how it is supposed to work as mine doesn't but, I can tell you that I need to replace the relay. I haven't because I have found so many other things to spend the $100 on!
03-01-2004, 02:06 PM
#9
Instructor
Keith, Barry, OR Anyone
Before I buy this relay, I checked the electric lines running across the back window:
We found there were 3 sections on drivers side (top, middle, bottom) and one on the passenger site.
When I use the multimeter with the defroster switch on, I get a 12v signal between the middle section and passenger side section, but nothing on top or bottom to the passenger side section.
I also get a 12v signal from top to middle, and middle to bottom.
What is this telling me? Does it mean I need a relay? How can I test the relay.
Anyone who can help, thanks.
I dont want to waste money on a relay, becuase they are non-returnable.
Cheers,
Justin
Before I buy this relay, I checked the electric lines running across the back window:
We found there were 3 sections on drivers side (top, middle, bottom) and one on the passenger site.
When I use the multimeter with the defroster switch on, I get a 12v signal between the middle section and passenger side section, but nothing on top or bottom to the passenger side section.
I also get a 12v signal from top to middle, and middle to bottom.
What is this telling me? Does it mean I need a relay? How can I test the relay.
Anyone who can help, thanks.
I dont want to waste money on a relay, becuase they are non-returnable.
Cheers,
Justin
03-01-2004, 02:41 PM
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As has been said, it is a two stage defroster. When you pull the switch out to the first detent, only the middle is energised. Pulling the switch out all the way energises both middle and top/bottom circuits. So, if the relay is faulty this can happen. Also, if--like some of us with older cars--all the traces on the window are open due to damage, this can stop part of the defroster from functioning. To find out, pull the switch 1/2 way, test for power @ the window connections. Then pull it out al the way and test again. If you have power at one point on low, and all points on high, the relay is OK. If not, confirm you have continuity through your window traces then replace the relay.
D Gaunt
D Gaunt
03-01-2004, 04:01 PM
#11
Instructor
I think you are talking about older cars. On my car I press a button, and it pops out. There is no other setting that I am aware of. I don't want to go outside and check, but I'm pretty sure its either on or off and no two stages.
Can someone confirm this? I have an 89 3.2 Carrera.
Can someone confirm this? I have an 89 3.2 Carrera.
03-02-2004, 03:26 PM
#12
Instructor
Just put the relay back in, and now none of the rear window demists 
Before it was just the centre part. Any ideas anyone? Is it definately the relay being the problem?
Cheers
Before it was just the centre part. Any ideas anyone? Is it definately the relay being the problem?
Cheers
03-02-2004, 03:27 PM
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Probable right about the older car thing. I have a two stage pull/push switch. Perhaps a newer car wonder can tell how it works. There must be a way, if it is still a two part defroster, unless they use a thermal sensor or something?
03-02-2004, 06:02 PM
#14
Instructor
Hi,
I've seen this part advertised on www.berlyn-services.co.uk/
RELAY 2 STAGE HEATED WINDOW
PART NO. 911.615.115.00
It is described as a 2 stage relay (what does this mean? centre and top/bottom?)
Anyway, it is the SAME part nmber as the relay I have (1989 model 3.2)
Maybe I'll just buy it (I can't get to the connections on the window under the rubber seals, too tight I think)
Cheers,
Justin
I've seen this part advertised on www.berlyn-services.co.uk/
RELAY 2 STAGE HEATED WINDOW
PART NO. 911.615.115.00
It is described as a 2 stage relay (what does this mean? centre and top/bottom?)
Anyway, it is the SAME part nmber as the relay I have (1989 model 3.2)
Maybe I'll just buy it (I can't get to the connections on the window under the rubber seals, too tight I think)
Cheers,
Justin
02-22-2008, 06:50 PM
#15
Instructor
Folks,
After 5 years (you can see where this went with regards to priority for me!) I back on to this.
Does anyone have electrical knowledge of the relay (911.615.115.00) used in this circuit? I'm confounded by its design. Bentley has a good representation of the circuit on page 970-55 in the wiring diagram section.
This 'relay' actually has TWO relays built in and here's what I've deduced so far. Power (+12V) for (and only for) the window elements themselves is provided through pin 30 on the unit and is always hot. The opened/closed state of the two relays dictates whether or not this voltage is appliled to the heating element segments.
Ground is provided to the unit on pin 31. One relay has its positive connection on pin 86 and when voltage is applied to this pin (as when the defog switch on the center console is depressed) the relay closes and provides voltage to ONE section of the three-section heating element via pin 87. This relay is very simple in that it should always have a ground (pin 31) so given voltage on pin 86 you should see pin 30 voltage immediatey appear on pin 87.
The second relay has its positive connection on pin 86a which is 'ganged' to pin 86 via the wiring harness so when 86 has voltage so should 86a. If the relay closes, pin 30 voltage is destined to appear on pin 87a which is routed to a SECOND section of the heating elements. This section is 'ganged' to the remaining THIRD section so in design this second internal relay actually controls TWO of the three heating elements.
What's different with this 'second' relay is that its access to ground is in no way as simple & direct as the first relay. THIS relay has additional circuitry (8 resistors, 2 diodes, 1 capacitor and three transistors) that appear (?) to determine whether or not this second relay gets the ground it needs to operate.
In my case I can get BOTH internal relays to close by providing +/- to their appropriate component pins directly on the circuit board they are mounted on, so I know the windings of the relays are good. Their contacts also pass voltage from pin 30 when doing so, so the relays themselves appear to be fine.
With regards to the second relay's additional circuitry, one resistor appears to be way out of spec and the two diodes are questionable but I don't know their composition or forward/reverse bias specs. The three transistors are another question and I don't know their pinouts (EBC) or design although two are the same with one having a different part#.
In short, the 86-87 relay always works but I can't get the 86a-87a relay to operate unless I bypass its additional circuitry. Why oh WHY is this second internal relay 'blessed' with this extra crap???
What oh WHAT is this 'extra crap' attempting to do with the two heating element segments it controls???
Why do I care? 1) The relay cost: US100.00+ 2) I haven't spent US100.00 in beer on this problem yet. I have a rule that states don't buy a new electical part to replace something that's 'repairable' until the cost of 'trouble-shooting beer' exceeds the cost of the new part. ;-) Anyway, after getting into this I JUST HAVE TO KNOW... why is this thing SO DAMN COMPLICATED???
Barry
Who could work on this for years 'cause Bud-Light's pretty cheap hereabouts...
After 5 years (you can see where this went with regards to priority for me!) I back on to this.
Does anyone have electrical knowledge of the relay (911.615.115.00) used in this circuit? I'm confounded by its design. Bentley has a good representation of the circuit on page 970-55 in the wiring diagram section.
This 'relay' actually has TWO relays built in and here's what I've deduced so far. Power (+12V) for (and only for) the window elements themselves is provided through pin 30 on the unit and is always hot. The opened/closed state of the two relays dictates whether or not this voltage is appliled to the heating element segments.
Ground is provided to the unit on pin 31. One relay has its positive connection on pin 86 and when voltage is applied to this pin (as when the defog switch on the center console is depressed) the relay closes and provides voltage to ONE section of the three-section heating element via pin 87. This relay is very simple in that it should always have a ground (pin 31) so given voltage on pin 86 you should see pin 30 voltage immediatey appear on pin 87.
The second relay has its positive connection on pin 86a which is 'ganged' to pin 86 via the wiring harness so when 86 has voltage so should 86a. If the relay closes, pin 30 voltage is destined to appear on pin 87a which is routed to a SECOND section of the heating elements. This section is 'ganged' to the remaining THIRD section so in design this second internal relay actually controls TWO of the three heating elements.
What's different with this 'second' relay is that its access to ground is in no way as simple & direct as the first relay. THIS relay has additional circuitry (8 resistors, 2 diodes, 1 capacitor and three transistors) that appear (?) to determine whether or not this second relay gets the ground it needs to operate.
In my case I can get BOTH internal relays to close by providing +/- to their appropriate component pins directly on the circuit board they are mounted on, so I know the windings of the relays are good. Their contacts also pass voltage from pin 30 when doing so, so the relays themselves appear to be fine.
With regards to the second relay's additional circuitry, one resistor appears to be way out of spec and the two diodes are questionable but I don't know their composition or forward/reverse bias specs. The three transistors are another question and I don't know their pinouts (EBC) or design although two are the same with one having a different part#.
In short, the 86-87 relay always works but I can't get the 86a-87a relay to operate unless I bypass its additional circuitry. Why oh WHY is this second internal relay 'blessed' with this extra crap???
What oh WHAT is this 'extra crap' attempting to do with the two heating element segments it controls???
Why do I care? 1) The relay cost: US100.00+ 2) I haven't spent US100.00 in beer on this problem yet. I have a rule that states don't buy a new electical part to replace something that's 'repairable' until the cost of 'trouble-shooting beer' exceeds the cost of the new part. ;-) Anyway, after getting into this I JUST HAVE TO KNOW... why is this thing SO DAMN COMPLICATED???
Barry
Who could work on this for years 'cause Bud-Light's pretty cheap hereabouts...
