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OBC...again....!!!

colin129

colin129

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I know this has been posted before (I think I did about 3 yers ago!)

I have got the chance (finally) to buy an OBC to replace my Rev counter. I already have the column stalk fitted.

I understood that it was a straight plug-in swop and the only item which will not work will be the outside temperature display (which I can live without for the time being).

The guy selling it seems to think there is some sort of metal box control unit (his words) between the column stalk and the rev counter/OBC, is this the case or should I be able to simply swop them straight over?

Sorry for going back over this, but my quest is finally over and I'm getting excited [8|]
 
Hi Colin, there are two plugs already on your loom for the OBC. One is just behind the stalks. It's flat in shape and has about 4 wires. This plugs into a similar plug that comes off your 3rd stalk that controls the OBC.

The plug for the tacho is deep inside the dash and will be tie wrapped to the loom (mine was behind the speedo).

The OBC tacho will either be a MPH or KPH specific - so check which one he is selling as you can't swap between MPH and KPH.
 

ORIGINAL: Steve Brookes

Hi Colin, there are two plugs already on your loom for the OBC. One is just behind the stalks. It's flat in shape and has about 4 wires. This plugs into a similar plug that comes off your 3rd stalk that controls the OBC.

The plug for the tacho is deep inside the dash and will be tie wrapped to the loom (mine was behind the speedo).

The OBC tacho will either be a MPH or KPH specific - so check which one he is selling as you can't swap between MPH and KPH.
Click to expand...

Steve,

I have just spent most of the day going to see this OBC, which is indeed the genuine article & UK spec, bingo I thought, this is going to easy!

Oh dear, having removed all of the gauges on my car & had a good root around behind the dash, scrapped most of the skin off the back of my hands in the process, I simply couldn't see any evidence of there being another connector.

On the doner car the connector plug was fairly substantial & not that easy to miss and in fact I could see the connector plug for the non-OBC rev counter cable tied just a few inches further up the loom, clearly visible.

Either I'm blind or my loom, for some reason, does not have the connector plug for the OBC.

Any other ideas? Your help would be greatly appreciated.

Thanks

Colin
 
As yours is a 1990 like mine I can't see why it wouldn't be there. Get the negative battery terminal disconnected so you don't disturb anything and then with the tacho and speedo removed (at least) follow the current tacho cable to the main loom and then work your way from there. It's a long time ago since I did mine but I seem to remember the OBC plug being near the clock and possibly tied the other side of the loom (i.e. windscreen side).
 
Still can't see any sign of the plug connector.

I have looked at the wiring diagram from the Porsche manual, which shows the OBC and also the outside temp sensor, which I don't think works unless it was standard equipment.

Is it possible that your car was originally fitted with an OBC rev counter and had a standard rev counter fitted subsequently, does the option appear on the option codes for your car?

What is really baffling is that the car it came off, had the none OBC rev counter plug connector cable tied to the loom just a few inches down from where the OBC plug exited the main loom bundle.
 
No the OBC is not on my options list - my car's original spec was very basic. Others have also retro fitted the OBC by plugging it in just like me.

I almost gave up trying to fit mine when I saw that my normal tacho plug was different to what the OBC tacho needed and then spotted the tie wrapped plug when looking around with a torch inside the dash.

Is there any chance your car is a 90 model year that was made in 89 as there is a thought that 89 cars might have a different loom. Info about that and picture of the plug you're looking for at the link below:

http://forums.rennlist.com/rennforums/964-forum/559676-obc-plug-in-an-89-c4.html?highlight=OBC

Here's another thread about people retro fitting OBCs

http://forums.rennlist.com/rennforums/964-forum/174942-obc-retrofit-help.html?highlight=OBC
 
I fitted the obc to my car last year and it is like Steve says. The plug is clearly visible tied to the loom just behind the non obc connected. I would guess that your car may be an 89 model without the extra wiring present [:-]
 
My car was registered in February 1990 which would suggest an '89 build date, hence explaining the absence of the OBC connector. It must have been one of the very earliest built.

The Porsche manual wiring diagrams (Volume 7) gives the following section headings

Wiring diagram type 911 Carrera 4 model 89
Wiring diagram type 911 Carrera 2/4 model 90

Suggesting that the wiring should be there for 90 model years (which although built in 89, mine would probably be 90 model year). There is also wiring for e.g. Airbag present on the same diagram.

The answer therefore appears to be that the OBC connector was not added until later in the build year, I think that the 91 model year starts to be built in the final third of the year before.

Needless to say I am dissappointed as it has taken me ages to finally find a proper UK spec OBC.

I guess I'll have to spend the money on a G-pipe or something instead...[:D]
 
Colin, mine's a 90 model year as denoted by L in the VIN. It was made in April 90 but not registered until August 90. Officially 89 cars are denoted by K in the VIN and were made between August 88 and July 89 and were only C4s.

So as you can see I'm stumped as to why yours wouldn't have the plug [&:]
 
Mine also has an L in the VIN, but it has to have been built in 1989 to have been delivered & registered by the 14th of Feb (a Valentine's gift?).

Thing is I can't think of where else to look for the cable, I had all the gauges out, I felt all along the loom by hand & using a torch. I reached behind the ventilation pipe behind the instruments, I have look in the front boot where the loom enters, where there are several unconnected wires but none anything like the required connector.

Having seen the installation in the donor car, the plug for the non-OBC connector was right in front of you, not hidden at all, I even took a pic of it, you can see it in the middle of the photo with the OBC connector plainly visible. It is quite an obvious thing to miss.



936FB3B26B1C4C12B8CA77B1A728349D.jpg
 
You're right...the photo of the donor shows how obvious it is. Even being white(ish) compared to other plugs! Have you already bought the OBC and if so and if you can't fit it to yours, do you want to sell it?
 
I went to buy it with the intention of confirming it was working before parting with the cash, obviously I wasn't able to do this so didn't buy it.

It is currently on fleabay, but I think he will take somewhat less that the advertised price.

Readers my be interested (or shocked) to know that the car it came off, a Tip Cab, was damaged on the nearside quarter/front and written off, the guy reckoned it could have been repaired for £1K, but I would have put the figure nearer £5K or £6K, still far below the value of the car. Not sure why they wrote it off, but once written off, they have to cut it in half and take out a section, to stop anyone from reselling it, sad to see the car in half like that.
 
I have a electrical drawing for wiring it up if you don't have the plug. You would need the plug from the donor car though. It's easy ish to wire. Do you have the plug for the stalk? I fitted obc the other week and my plug was difficult to find. In the end it was tied behind the speedo. Next I am retrofitting cruise control!

Tim
 
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