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Anti-lock brake light on and Speedo Stopped
#1

Took the car into TRE and they checked the anti-lock brake sensor and it checks out just fine. They figure that one has to do with the other sense it happened at the same time and are going to research it but I thought I'd ask here to see if anyone has run into the same problem. I also read that the speedo signal does a loop through the alarm unit, afaIk, alarm is working properly because I just set it off recently. [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

Anybody?

TIA,
Mike D.
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#2

I would check the plug on the ABS computer, the speedo will stop and the anti-lock light will come on if it is unplugged. IIRC, the speedo gets it signal from the right front wheel sensor. Check that sensor, the grounds for it and the ground connection near the ABS computer. It is possible the ABS computer has gone tits up but is more likely a wiring/sensor issue.
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#3

Thanks for the info, can you tell me where the abs computer is?

thanks again,
M
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#4

It is in on the side of the passenger footwell (in front of the door, below the dash).
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#5

Just this evening, fired up the engine and have the same symptoms.........

Damn too.

Will check this sunday what the problem is.

It all started with the speedo working once a while for 10 kilometers etc. After shutting down the car and a fresh restart the speedo worked. Nowadays the speedo has gone and the ABS signal and the big <!--sizeo:7--><!--/sizeo-->! <!--sizec--><!--/sizec-->is on the dash.
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#6

Unknown4u - Did you ever get any answers for this problem?

TRE was never able to figure mine out, so I'm going over to pick it up today or tomorrow. I have a call out to a service manager at Rusnak Porsche, dreading taking the car there just because of the $$$$.

frustrated!

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#7

i might be able to find it with the durametric - feel like a road trip to OC? we could plug it in and check it out
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#8

Maybe I'll just wait for the Fun Run day. I don't need to know how fast I'm going unless Johnny asks, and when he does he already knows... [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]
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#9

No answers for the moment.
Have not done the search either because I left for 2 weeks of holiday..........

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#10

i suspect a bad connection at the dash - those connectors are known to come loose, especially if somebody has been in there before - the ground back there is also suspect - i would check those before dropping it off

have you done a blink test yet?
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#11

This is likely to be a bad connection to an ABS wheel sensor, most likely damaged wiring to one of the front sensors... I think the front left sensor (USA Driver's side) is the one the speedo uses. These connections get beat up from turning and bumps, etc. Easy enough to take the wheel off, pull the sensor connection and ohm it both ways.

You can also put a DMM set to AC volts on each of the wheel inputs to your ABS computer to read the voltage from each wheel. You need to do this while driving around slowly so the wheels are turning and generating that voltage. If there is a bad connection that wheel will probably not show a significant voltage.

-Joel.

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#12

good point - they do get very dirty and if the cover on the connector is damaged or loose, it can foul the connection
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#13

ok, found one other problem that may be related.

I notice that the alarm is not turning on when locking up with the key. It used to when speed was working and anti-lock light was not lit.

Here is what I know,

Speedo works off anti-lock sensor, signal runs through alarm, alarm is not setting. I read in the owners manual that the alarm sets when when doors, rear hatch, hood and glove box are closed. How would the alarm get a signal from the glove box and hood? I recently unplugged the lights from the glove box and front hood because battery was running down. Could any of this possible be related?

And the blink test came up with "anti lock brakes" code.


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#14

glove box and hood are also connected to the alarm via the current sensing for the lights
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#15

I did not have had really time to investigated the problem. Still driving with the big ! and nog speedosignal.
I have to change the wheelsensor I suppose. Will start to do that after the first of october when having more time.
Maybe it could be alarmrelated but I guess it is stll a sensor problem.
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#16

OK, so after months of messing around and 3 shops checking out the 968 it is finally fixed! (almost) Turns out the problem was in the relay/fuse panel under the hood. By the end I had no power locks, no ABS, no cruise control, no brake lights, no alarm, no speedo and probably something else.... The guy said the fuse panel has a short and he could get a new from Porsche, $500. Uh, let me look around. I found one on ebay, same year 968 part, good for me. I actually called Rusnak and asked about the P/N and found out that it was the same from '87 944 thru '95 968. Anyway I have everything back online and working except for the Oil Level sender and light in on on the dash. And, I have to go back to the first shop who did belts, rollers, seals etc. etc. etc. because they have to readjust balence belt. It is WAY off and flapping around.

Anyway, I took apart the old relay/fuse panel, I'll take a couple of pics and post them as soon as I figure out what forum to post stuff like that in. [img]style_emoticons/<#EMO_DIR#>/cool.gif[/img]

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#17

I didn't have had time to give an update of my problem. But I was the wire and I changed the abs sensor from the front wheel as well to be sure the problem has gone. Some animal has just eaten it.......
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