Hi,
I have a 1985 280SL (UK RHD). Just bought the car and it was running fine. The wiper switch was acting weird so I changed the indicator stalk and then the wiper relay - now the wipers are running fine. I also took the opportunity to change the dash bulbs while I was there. However, since doing this, I have a new problem with the ABS. When turning the ignition on, the ABS light flashes twice and then goes out, then all the other lights come on (such as alternator, brake wear, etc). The car then starts up fine, however warm idle seems to be at just over 1000RPM. As I have only owned the car briefly, I think the idle was fine before. I have checked the OVP relay fuse and even swapped the OVP relay with a used one off eBay - however I can only presume that it is not faulty also. I have also changed all the fuses now on the car just in case.
It should come on with all the others, stay on for a short while, and go out. If the change in behaviour is definitely coincident with the changing of the bulbs and stale, then I'm gussing you upset something. The connector block at the back of the dash can be a bit fractious if not fully home, and there isn't much slack in the wiring.
Is the idle 1000rpm in neutral, or in D. If in neutral, then that's what happens when you take the 'drag' of the autobox off the engine. With it in D and you clamping down on the footbrake, you should be idling between 700-800rpm. With these older fuel-injected models, the electronincs don't differentiate between a loaded and unloaded idling motor, like they do on the more modern stuff.
when Cold, in neutral, mine will idle up to 1100rpm, then work itself down to about 900-950 as it warms up. That equates to about 800 in D, down to about 650 when fully warm.
It should come on with all the others, stay on for a short while, and go out. If the change in behaviour is definitely coincident with the changing of the bulbs and stale, then I'm gussing you upset something. The connector block at the back of the dash can be a bit fractious if not fully home, and there isn't much slack in the wiring.
Is the idle 1000rpm in neutral, or in D. If in neutral, then that's what happens when you take the 'drag' of the autobox off the engine. With it in D and you clamping down on the footbrake, you should be idling between 700-800rpm. With these older fuel-injected models, the electronincs don't differentiate between a loaded and unloaded idling motor, like they do on the more modern stuff.
when Cold, in neutral, mine will idle up to 1100rpm, then work itself down to about 900-950 as it warms up. That equates to about 800 in D, down to about 650 when fully warm.
Its idling at 1500 when cold coming down to just over 1000 when warm in Park. It used to idle at 700-800 I think. I tried to post the link to the video of the lights. Try this instead:
That does sound bad. and possibly expensive. I know mine's a V8 and not an I6, but when i bought it, it had the same high idle. I knew that was the air-by-pass valve, and i had limited results fixing it, and ended up popping for another from a used parts dealer.
If you've not put the steering wheel back on yet, just slip the cluster out again and check your multi-pole block connector is home properly. When mine wasn't ( the first time I did the job), I had all sorts of indicator and hazard light gremlins.
I'm afraid I'm going to have to advise you use the search function, as you now have the sum of my experience on these faults. Sorry mate.
Thanks. The ABS light is wired separately to the rest of the cluster. I am pretty sure I have checked everything at the back but I'll have another look. If you see the video, it almost looks like some kind of short with the brake wear light as that does not come on until the ABS light goes out. It fixed itself once yesterday until I changed the rest of the bulbs so I tried seeing if there was something lose but to no avail. Might be an earth? Does anyone have a wiring diagram of the ABS system as the Haynes manual is pre-ABS.
it does look wierd mate. I'd be definitely looking at the back of the cluster again. with some contact cleaner spray handy as well. slip the connector off, give it a squirt and reassemble.
Looking at the wiring diagram, I think this may have happened: the charge/alternator bulb holder fell apart, so I put it back together. It did not light first time so I figured I got the pins the wrong way around as there is a lead only on 1 pin. I presume it picks up earth from the cluster housing. I turned the pins around and it worked fine the 2nd time. Maybe this shorted pin 15 on the ABS control unit to ground damaging it?
I will remove the battery and see if it resets things. The light blinking is almost like the ABS ECU trying to start up but failing I am guessing. Are the ECUs expensive? Do they need to be coded to the car or will any ECU from the same era do?
No, circuit 15 is +12V after the ignition switch. If you look carefully at the drawing you will see a reference to circuit 61, it is connected to the generator and all the other dash lights (low side).
The ISC is located behind the glove compartment, see attached figure (N8), pop plastic rivets to remove inside liner.
I've pulled the bulb and reinserted it a few times. What I think is odd is that the brake wear indicator does not light up until the ABS light has done its thing.
If it's not a change in the wiring as a result of the lamp holder reconstruction, my money is still on the OVP relay. If we are getting faulty electrical parts when purchased new, there's no guarantee that a used item from eBay will be perfect.
I do have a 1984 500SL - I presume the OVP is the same? Could try swapping it but there is no guarantee that it is fine as its a car in need of restoration.
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