The horn by the heater blower won't stop!

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Brucey
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Post by Brucey »

Note that the OBC display is not an LED display; it is a backlit LCD display. Often the backlight fails or goes intermittent but the OBC continues to function. You can tell this by using an angled light to examine the OBC display when it appears to be 'off'; you will still just be able to read the numbers if the OBC backlight only has failed.

Note also that the way the OBC is configured is done in at least two different ways depending on the age of the car, so you need to be 100% sure which parts you are dealing with. I think there was a significant change around the date of the OP's car.

Just assuming that 'you have an 83' or whatever isn't good enough, you need to use the chassis number to find the exact build date and then identify which parts you should have according to the ETK. Having done that, compare the parts you have with photographs of the exact same part numbers to be sure.

cheers
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songzunhuang
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Post by songzunhuang »

Brucey wrote:Note that the OBC display is not an LED display; it is a backlit LCD display. Often the backlight fails or goes intermittent but the OBC continues to function. You can tell this by using an angled light to examine the OBC display when it appears to be 'off'; you will still just be able to read the numbers if the OBC backlight only has failed.

Note also that the way the OBC is configured is done in at least two different ways depending on the age of the car, so you need to be 100% sure which parts you are dealing with. I think there was a significant change around the date of the OP's car.

Just assuming that 'you have an 83' or whatever isn't good enough, you need to use the chassis number to find the exact build date and then identify which parts you should have according to the ETK. Having done that, compare the parts you have with photographs of the exact same part numbers to be sure.

cheers
Brucey, thanks for chiming in.
I do have comment though. Are you sure my OBC display is not a red LED display? I've replaced the bulb back there and lights up the keypad, but does nothing for the numeric display. In fact, in my side by side picture you can see how it all keypad keys are lit even when the display is out.

Also, given how the numbers are segmented when they do light up, it really looks like an LED. LCD have a very distinct look to them. There's also a little dot of red that lights up when the time is PM. It's just left of the display itself. That's got to be an LED and it matched the numerals exactly.

Looking at the info I've been able to dig up, I had a suspicion that all the computer setups were not the same. It'll take some digging to see which one I actually have.

I have a downloaded manual for a M6 and there's mention of a chime locate above the glove box (close to the OBC) that comes on when you exceed a certain speed or when the temperature drops to a certain point. I guess it's a warning chime to let you know when you are speeding or if there may be ice on the road. I've seen these thing in other cars. However, in my case, it just chimes when I turn the ignition key. I haven't heard it at other times.

The adventure continues.
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Song Huang
1984 633CSi
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Brucey
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Post by Brucey »

OK if your display is self-illuminating you may have a gas-plasma display there (or indeed an LED as you say); early model OBCs (with which I am less familiar) maybe had those but later ones had LCD displays for sure.

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songzunhuang
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Another piece of the puzzle

Post by songzunhuang »

I drove the car almost 100 miles today. After the first 45 miles, the OBC display came back on again. I took the car to a place for lunch and then drove all the way home without a hiccup.

During my drive I checked the outside temp, range, mpg and I timed my drive home at 48 minutes. It all worked perfectly.

Emboldened by all this goodness. I left the car running for a moment when I got home and opened the hood to plug in the horn. Guess what? It did not blare. While the OBC display was working just fine, the horn wasnt triggered.

Last night when the display was not working, I also tried to hook up the horn and it blared like crazy. There is some link between whatever is disabling the display and what is triggering the horn.

This is going to be a tricky one to find. I'm thinking that it's something in the wiring. Perhaps something is occasionally causing a short circuit, but not enough to burnout any fuses.

Anyone ever have similar symptoms in their OBC? This may take a while to find. Meanwhile I have driven over 150 miles on this tank of gas and my fuel gauge still says its full. OBC says i have 147 mile range left. Does this mean a full ta of gas is good for 197 miles? Hmmm...maybe time to check the sender.
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Song Huang
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baders
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Post by baders »

Song you need to pull that On Board Computer box and take a good look at it. You said you have pulled it apart to replace a fuse before ?

The OBC gathers the fuel level from the sender unit in the tank. It uses this to calculate range. The sender is easy to check, as per Bentley. I made up a potentiometer unit for my testing, simulating the sender.
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songzunhuang
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Post by songzunhuang »

baders wrote:Song you need to pull that On Board Computer box and take a good look at it. You said you have pulled it apart to replace a fuse before ?

The OBC gathers the fuel level from the sender unit in the tank. The sender is easy to check, as per Bentley. I made up a potentiometer unit for my testing, simulating the sender.
Yes I pulled it before, opened it up and replaced the burnt fuse. At the time, I thought envy thing in the Seimens box looked exceptionally clean. It had been well protected.

I'll pull it again and take a close look. I'm thinking that I need to look for something that is "relay" like and looks burnt. Not sure what else to look for at this time.

I hope I have time to get to it this weekend.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383
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Brucey
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Re: Another piece of the puzzle

Post by Brucey »

songzunhuang wrote:
Last night when the display was not working, I also tried to hook up the horn and it blared like crazy. There is some link between whatever is disabling the display and what is triggering the horn....
I think this has to be either a failure of the power supply to the OBC or a failure of the internal power supply (it will be converted to 5V internally I think) within the OBC.

Doubtless the system is designed so that in the event of a partial failure of the security system (which could be an attempt to bypass it) the horn sounds; probably this would be done by using a 'normally closed' relay.

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songzunhuang
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Re: Another piece of the puzzle

Post by songzunhuang »

Brucey wrote:
songzunhuang wrote:
Last night when the display was not working, I also tried to hook up the horn and it blared like crazy. There is some link between whatever is disabling the display and what is triggering the horn....
I think this has to be either a failure of the power supply to the OBC or a failure of the internal power supply (it will be converted to 5V internally I think) within the OBC.

Doubtless the system is designed so that in the event of a partial failure of the security system (which could be an attempt to bypass it) the horn sounds; probably this would be done by using a 'normally closed' relay.

cheers
So crazy. After a few days of not working and chiming unpredictably, my OBC came back on again today and it's working correctly. For now.
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Song Huang
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Re:

Post by KINGJOHN808 »

songzunhuang wrote: Fri Nov 13, 2015 5:15 am
baders wrote:Referring to the above diagram, look for the box with a C1 plug (there should also be a C2 plug) and a brown/yellow wire going to pin 17, that be your culprit. Indeed, this box http://www.ebay.com/itm/NEW-OEM-BMW-658 ... 1554229734 has two plugs :D
Thanks guys. You've confirmed what I suspected thus far. The panel is definitely the thing in the dash with the buttons and LED display.

The main control unit has the 2 plugs, just like the picture you linked to on eBay. It was this unit that I removed a while back and replaced a fuse, which resulted in everything turning on and working for about a month.

The current behavior has got me really confused. I've noticed a few odd things.

1. When the LED display is NOT working, turning power on via the ignition switch will result in a chime that I swear is coming from the display. The display doesn't work, I just hear a chime that I've never heard before.

2. On the way home today, the LED panel turned on again! I set the time to 7:33pm and it was fine for about 2 minutes. Then it shut it self off again. What?

I thought that the dead display may have been my fuse again, but the fact that it came on for a few minutes kills that theory.

Meanwhile the ETM scan shows something interesting. The OBC horn is clear on the left (upper part in the picture), However there's another thing at the lower left labeled as an "Alarm Horn Control". What that? I can't tell from the diagram if it's a separate part of if it's part of the main control unit. Any ideas?
Question about the OBC. I changed the fuse, the OBC now works (time, temp, etc). However, the buttons do not illuminate. I know the bulb is good because I checked it by applying 12v directly to it (the bulb). Also, changed the bulb multiple times with multiple different bulbs (all known to be good).

Still no illumination. Checked the “pad” where the bulb housing attaches and appear to have power (10.7 VDC). I’m completely stumped at this point. All other lights work around the dash and the temp control sliders, just the OBC buttons do not illuminate?

What’s the secret or what am I missing?
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