OBC malfunction - a tricky one

[AndrewL]

Here's a challenge: my OBC gong works fine on the ice alarm but won't gong for the over-speed indicator.

The OBC appears to accept input of the desired speed limit and the red LED on its front flashes as it should if you exceed that - but no gong.

Any suggestions welcome. Has Brian disassembled an OBC?

Andrew

[316eyes]

"Has Brian disassembled an OBC?"

More than likely; if he hasn't he will know a man who can/has.

Patience, patience.

Superspark will no doubt arrive soon.

Over to you, Brian.

[tailoutcharlie]

bloody things, i cant change the time on mine so i have to wait till midnight to reset the clock, then it shows the right time....until i disconnect the battery again!

[AndrewL]

Odd.

Mine's pefect apart from the speed gong which I'd appreciate.

[tailoutcharlie]

tell you what you have my gong and ill have you clock, i really should buy a watch.

[AndrewL]

Get a replacement unit I suppose. I could do that but mine is cosmetically in very good condition.

[tailoutcharlie]

tbh everything else works on mine too, just havinga monday night...sorry tuesday morning moan.

good luck with your prob AndrewL.

[Brianmoooore]

Has Brian disassembled an OBC?

I've disassembled a gong and repaired it, but never an OBC. Never had reason to.
Very strange fault. Probably just a diode gate inside the OBC that's failed, but finding it would be fun. Gong operates by momentarily earthing the control wire. (Other two wires are earth and power).

[AndrewL]

Ah well. Thanks very much Brian. I might see if I can easily swap the clean face I've got on my OBC for a working back part I've got spare.

[orangecurry]

no you can't - I have taken OBCs apart, hoping to be able to replace worn buttons on an otherwise perfect OBC - but they are not designed to swop bits over. And take lots of photos as you dismantle, otherwise you'll struggle to get it back as it was

[AndrewL]

Thanks. I've got one that some cretin on ebay levered out of the dash 'coz he could figure out how it unscrewed. I'll practise on that.

[Royalratch]

Was directed to this thread as my OBC has the memory of a goldfish.

I set the date and time and it lasts between minutes and a max of 24 hours before resetting to flashing '----UHR'.

The Gong is attached and works fine. The temp sensor and alarm horn are not attached.

Why is this happening? Faulty OBC? I appears to work fine otherwise...

[Alyman]

Interested to see if there's an answer to this - my OBC does the same thing. Every time I set the time then turn the engine off the time and date reset to the flashing UHR scenario...

[Royalratch]

But mine does it randomly.

I can leave it over night and it still has the time set or it can reset in minutes.

Never lasts more than 24 hours tho.

It's deffo the OBC as I've fit this to 2 different cars and it's the same with both.

Really P-ssing me off!

[Brianmoooore]

If my wiring diagrams are correct, there is no permanent live going to the OBC, so there must be a rechargeable battery or large capacitor inside the OBC to power the essential electronics when the ignition is off. Would imagine it's a problem with this.
On the other hand, doesn't an OBC reset if you disconnect the battery?
If that's the case, then there must be a permanent live!
There's a red/white wire from pin 23 on the yellow cluster connector, but my diagram doesn't show any connection to this pin inside the cluster.
If C23 on the cluster is permanent live, then it must come from pin A2, via fuse 21, as that's the only permanent 12 volt feed to the cluster.

[Royalratch]

So are you saying check fuse 21?

Or open it up and look for a battery?

[Brianmoooore]

So are you saying check fuse 21?

Or open it up and look for a battery?

Don't know - don't trust my wiring diagrams!
Does the OBC loose its settings (a fully working one) if you pull fuse 21 or disconnect the battery?

[Royalratch]

Don't know.

I'll check that fuse tho.

[Royalratch]

Fuse 21 looks fine.

I set it again today then after 3 minutes of driving the going sounded and it reverted back to flashing temp reading.
I should reiterate here that I have now connected the temp sensor yet - would this affect the settings permanency?

Also, we're not talking about the relay here - could it be that? What function does it serve?

Shame to toss the OBC as it looks and works like new except for the fact that it does'nt work at all!

[Brianmoooore]

Relays are to do with the CODE alarm function only.
If temp sensor is not connected, the gong should sound every time you turn the ignition on, and the display should read some very low temperature.

[Royalratch]

It does exactly that.

Is this confirmation the thing is faulty and I should just get a new one?

This is how I set it, just to be sure it's not that:

Press SET pin with pen.
Set time / date and Imperial / metric etc!
Press SET pin again so separator dot appears.

All is well. Then within 5 minutes the gong chimes and it resets!

The manual does say it will lose settings when disconnected / battery is removed.

[Royalratch]

One more thing - some dude told me (and I just confirmed it on the ETK) that BMW never offered the OBC for 4 cylinder models.

Does this mean it will never work?
I can't see why it wouldn't but has anyone got an OBC fitted to a 4-pot E30 and can confirm it works?

[tomtomiS]

ive heard that u can buy the right coding plug for a 318is. curious to hear the result of this as i was gonna put my obc kit in my one

[tomtomiS]

try this link, its got a chart saying which engine uses which coding plug
http://www.e30zone.net/modules.php?name ... oding+plug

[AndrewL]

I vaguely remember that the 316, not being fuel injection, didn't have the right electronics/sensors to drive the OBC but the 318i did.

Someone more knowledgeable will be along shortly to confirm or demolish this.

[tomtomiS]

looks like the iS needs a 4-1 plug to work properly
the 316 seems to be the only one not listed

[Royalratch]

So the 318iS needs the 4-3 type, according to the chart.

I'll ring the dealer for one - tho this may give more accurate readings I'm not sure it will fix the random resetting - maybe tho...

Good find lads.

[Royalratch]

Number 2 - PN: 65 81 1 394 111

[Alyman]

From what I've heard the OBC was not an option on 4 pot models in the UK, but was in Europe. For example, the 318i requires a type 4-2 coding plug. To retro fit the OBC you'd need to get your local BMW dealer to get the coding plug sent over from Germany.

[Royalratch]

Already on hold to order this sucker!

Got my lottery win at the ready...

[Royalratch]

Okay.

Ordered the 318iS OBC coding plug which came in at £38 plus VAT.

My Touring is a M40 318i.
I should use the donor 318iS clocks too so that coding plugs match?

There's only 5000 miles between them anyway...

[Brianmoooore]

I should use the donor 318iS clocks too so that coding plugs match?

Clocks are all the same - just the coding plug on the front is different.

[Royalratch]

You mean coding plug on the back right?

[Alyman]

Nope, he means on the front. When the clocks are out, look at the area just under the battery symbol. There'll be a removable coding plug there. At least thats where it is on the three sets of clocks I've got kicking about.

[Royalratch]

You're right.

And so is is Brian obviously.

Have ordered the 318iS coding plug so will make sure that it's used with the 318iS clock plug too.