Stop light warning: intermittent problem
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From: Lymington, UK
Stop light warning: intermittent problem
Hello all. My first post...
I have an 84 'S' RHD Euro auto. The stop lamp warning light intermittently comes on triggering the main warning lights. Most the time it's on but sometimes it goes off - usually when I've been driving the car for over a half hour or so. In line with recommendations on previous threads I've checked and cleaned all lamp connections, i've checked all lamps are operational and the stop lamps are an identical specification. I've dismantled the lamp controller and cleaned all connections and the back of the PCB and checked for any solder breaks by eye - there didn't seem to be any visible problems.
I'm not sure what to do next - is there any way of testing the lamp controller? Can anyone offer me any much needed advice
Thanks Tim
I have an 84 'S' RHD Euro auto. The stop lamp warning light intermittently comes on triggering the main warning lights. Most the time it's on but sometimes it goes off - usually when I've been driving the car for over a half hour or so. In line with recommendations on previous threads I've checked and cleaned all lamp connections, i've checked all lamps are operational and the stop lamps are an identical specification. I've dismantled the lamp controller and cleaned all connections and the back of the PCB and checked for any solder breaks by eye - there didn't seem to be any visible problems.
I'm not sure what to do next - is there any way of testing the lamp controller? Can anyone offer me any much needed advice
Thanks Tim
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From: North Country
Tim,
I'm not sure on MY 84, but if you have a third stop light, has that been checked as well ?
Add:
Tim, it was rude of me - Welcome to the Tank.
I'm not sure on MY 84, but if you have a third stop light, has that been checked as well ?
Add:
Tim, it was rude of me - Welcome to the Tank.
Last edited by MainePorsche; Apr 29, 2013 at 08:30 PM. Reason: Welcome
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From: Philly PA
my suggestion to fix this you need to install new matching sets of bulbs
left and right sides should match .
Even though you may have all good bulbs swapping in new parts usually cures most lighting issues,
plus now you have spares for your VW or triumph
if you have a 3rd brake light ,though it didnt come out till 86 then replace this bulb as well.
Also check the connectors behind the rear edges of the quarter panels where the light cluster housing plugs in, look for dirty grounds.
check the bulb internal tabs for corrosion
left and right sides should match .
Even though you may have all good bulbs swapping in new parts usually cures most lighting issues,
plus now you have spares for your VW or triumph
if you have a 3rd brake light ,though it didnt come out till 86 then replace this bulb as well.
Also check the connectors behind the rear edges of the quarter panels where the light cluster housing plugs in, look for dirty grounds.
check the bulb internal tabs for corrosion
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Being a Euro, might need to make sure you have the later brake master cylinder and not the one that has the brake light switches on the bottom.
You should not have one like this
But if you do the switches on the bottom do go bad.
You should not have one like this
But if you do the switches on the bottom do go bad.
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From: North Country
You've said you inspected and all the lamp/bulb connections, and all are good. This should include the inner tabs and the wiring outside the fixture. Especially track brown wire(s) to its ground point.
The matching bulbs are relevant too. The lamp controller compares current to each pair of bulbs, and if there is a discrepancy than the controller registers a fault to central warning. Even if bulbs are of same specification there could be enough of an amperage difference that the lamp controller will sense.
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Thank you very much for your suggestions. I don't have a third brake light. I did install new matching stoplight bulbs. I also cleaned all the little tabs in the bulb holders. So i'll check brake master cylinder for type. Ill also check the grounds. Are these separate to the connectors that are found behind the rear quarter panels (which I sprayed with switch cleaner). If so, how do I access these grounds to clean them?
Is it worth me replacing the turn signal lamps too so they match - would they register a 'stop light warning'?
Cheers Tim
Is it worth me replacing the turn signal lamps too so they match - would they register a 'stop light warning'?
Cheers Tim
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From: North Country
Thank you very much for your suggestions. I don't have a third brake light. I did install new matching stoplight bulbs. I also cleaned all the little tabs in the bulb holders. So i'll check brake master cylinder for type. Ill also check the grounds. Are these separate to the connectors that are found behind the rear quarter panels (which I sprayed with switch cleaner). If so, how do I access these grounds to clean them?
Is it worth me replacing the turn signal lamps too so they match - would they register a 'stop light warning'?
Cheers Tim
Is it worth me replacing the turn signal lamps too so they match - would they register a 'stop light warning'?
Cheers Tim
On my 87 my ground point for all tail lights is MP VI (6) the ground point in the spare tire well. I looked at your wiring diagram and you may be using two ground points. The other one for the rear end would be MP VII (7) which would be near the rear hatch motor. You would remove the tool panel for this. ALL GROUND WIRES IN THE 928 ARE BROWN.
Happy Hunting
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From: Vero Beach, FL.
Had a somewhat similar issue with a "Tail Light" error warning on an '88, but not the stop light warning you are receiving. You said that you have checked and cleaned all the light harness plug connections, but here's a link to the "tail light" warning problem anyway if it is of any help.
https://rennlist.com/forums/928-foru...long-post.html
https://rennlist.com/forums/928-foru...long-post.html
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From: Bloomfield, MI
On an 84 the turn signals are not monitored, only stop and tail and are two separate circuits on the lamp controler/monitor, if it had side markers they would share the same lamp monitor circuit as the tail.
Thinking this is the master cylinder switches given that you changed the bulbs and cleaned connections.
although I'm not certain which mc is fitted on an 84 euro.
Edit: it could also be a failing lamp controller, does it show any signs of corrosion, may want to dissemble and try re soldering the connections. I tried once and it didn't fix it.
Dave
Thinking this is the master cylinder switches given that you changed the bulbs and cleaned connections.
although I'm not certain which mc is fitted on an 84 euro.
Edit: it could also be a failing lamp controller, does it show any signs of corrosion, may want to dissemble and try re soldering the connections. I tried once and it didn't fix it.
Dave
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From: Lymington, UK
Hi all
Following your suggestions I had a further look this evening but still haven't solved the problem.
My brake master cylinder looks as follows and looks to be in good condition with no corrosion around the contacts
http://www.flickr.com/photos/95398996@N02/8700089722/
I checked and cleaned the earth going to the wiper system (top right of below photo), which was quite dirty and a bit loose. This is now clean and tight. Here's the view in the boot of the car. Does this all look normal? (apart from the Land Rover battery the previous owner must have installed!) There doesn't seem to be an earth in the battery compartment - there is a bolt hole at the rear so is something missing here?
http://www.flickr.com/photos/95398996@N02/8698978937/
Both the rear connectors seem clean with no connections pushed in or dirty. I gave both sides a clean anyway with switchcleaner.
http://www.flickr.com/photos/95398996@N02/8700116548/
So, here I am and still haven't solved the problem. Perhaps it is the lamp controller, which didn't look dirty or corroded when I took it apart. Unless anyone has any other suggestions I may have to try and find a working lamp controller to test - if it works and the warning light goes off then I need to buy myself a new one...
Many thanks for advice so far, Tim
Following your suggestions I had a further look this evening but still haven't solved the problem.
My brake master cylinder looks as follows and looks to be in good condition with no corrosion around the contacts
http://www.flickr.com/photos/95398996@N02/8700089722/
I checked and cleaned the earth going to the wiper system (top right of below photo), which was quite dirty and a bit loose. This is now clean and tight. Here's the view in the boot of the car. Does this all look normal? (apart from the Land Rover battery the previous owner must have installed!) There doesn't seem to be an earth in the battery compartment - there is a bolt hole at the rear so is something missing here?
http://www.flickr.com/photos/95398996@N02/8698978937/
Both the rear connectors seem clean with no connections pushed in or dirty. I gave both sides a clean anyway with switchcleaner.
http://www.flickr.com/photos/95398996@N02/8700116548/
So, here I am and still haven't solved the problem. Perhaps it is the lamp controller, which didn't look dirty or corroded when I took it apart. Unless anyone has any other suggestions I may have to try and find a working lamp controller to test - if it works and the warning light goes off then I need to buy myself a new one...
Many thanks for advice so far, Tim
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From: North Country
Tim,
The ground wire to the rear wiper is specifically the ground from the wiper.
That large black cable, with red tape on the ends, from the battery is the earth/ground of the battery.
Attached is a pic of where the ground point for the rear lights is located (MP VI) - MP is for masse punkt/ground point. Track the Brown ground wires from both rear light harnesses - the final path will lead to MP VI
Edit: Can't post an image now. As you have the spare tire out you will see wires on the front wall of the spare tire well. There will be two to three brown ground wires attached there.
The ground wire to the rear wiper is specifically the ground from the wiper.
That large black cable, with red tape on the ends, from the battery is the earth/ground of the battery.
Attached is a pic of where the ground point for the rear lights is located (MP VI) - MP is for masse punkt/ground point. Track the Brown ground wires from both rear light harnesses - the final path will lead to MP VI
Edit: Can't post an image now. As you have the spare tire out you will see wires on the front wall of the spare tire well. There will be two to three brown ground wires attached there.
Last edited by MainePorsche; May 1, 2013 at 05:36 PM.
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From: Lymington, UK
Okay, I'm like a dog with a bone now - this warning light is laughing at me on my daily commute...
Here are two photos of the front of the spare tyre well. There are no grounds connected to the vehicle - just two connectors. I can see the live wires connecting to the battery before going into the loom. Am I missing something? I did find the ground point diagram on the forum and I can't see anything in my car that might be ground point 6.
Tim
http://www.flickr.com/photos/95398996@N02/8699110483/
http://www.flickr.com/photos/95398996@N02/8699112095/
Here are two photos of the front of the spare tyre well. There are no grounds connected to the vehicle - just two connectors. I can see the live wires connecting to the battery before going into the loom. Am I missing something? I did find the ground point diagram on the forum and I can't see anything in my car that might be ground point 6.
Tim
http://www.flickr.com/photos/95398996@N02/8699110483/
http://www.flickr.com/photos/95398996@N02/8699112095/
Nordschleife Master
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From: North Country
No Tim,
This is my error. On your 84 my guess is that the rear ground point is elsewhere. Before you search for that bone by tearing up the rear, someone will chime in on the locus of the rear ground point for an 84. You do have to check the grounds to the rear lights. You should do a dissection to find the ground wires from both tail light fixtures. I'll bet this is where the issue is. If the lamp controller looks good and it has never gotten wet, it should be OK. If you did get water leak into that region you would have many issues for the CE panel lives there too.
This is my error. On your 84 my guess is that the rear ground point is elsewhere. Before you search for that bone by tearing up the rear, someone will chime in on the locus of the rear ground point for an 84. You do have to check the grounds to the rear lights. You should do a dissection to find the ground wires from both tail light fixtures. I'll bet this is where the issue is. If the lamp controller looks good and it has never gotten wet, it should be OK. If you did get water leak into that region you would have many issues for the CE panel lives there too.
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From: Lymington, UK
Brilliant, I found the cluster of ground points in the rear left quarter of the car and I really thought I'd cracked it as they were all white with powdery oxidisation. Sadly after cleaning them all up nicely the warning light is still coming on. So another area presumably to check is the connections to the back of the two rear light clusters. However, once the lens is removed I can't work out how to pull the holder forward so I can access the wiring connections behind. Don't forget I'm an OB! Can anyone help with this?
Thanks Tim
Thanks Tim