 |
|
|
1979-1993 & 94 Conv [Subscribe to Daily Digest] |
 | [Main C900 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: brake lights still coming on... Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 4 Aug 2005 09:54:19
In Reply to: brake lights still coming on..., michael [Profile/Gallery]
, Thu, 4 Aug 2005 08:57:20
Members do not see ads below this line. - Help Keep This Site Online - Signup
|
Some background-
There are three pressure switch settings on the ABS pump. If the pressure is below around 140 bar (atmospheres), the ABS pump comes on; it turns off at 180 bar. If the pressure is belwo 100 bar, the ABS and Brake Fluid lights come on to tell you that the pressure is getting low and you only have a few brake applications left.
As you may notice, 140 bar is higher than 100 - so during normal use, the pressure drops down to 140, the pump turns on, and the lights should never come on. They may come on when you first start the car, because the pressure can (normally) bleed down below 100 bar as the car sits.
The ABS/Brake Fluid lights coming on usually means that the pressure is low - below 100 bar. This is usually because the ABS pump isn't running. The pump may not run because it's tired or overheated, or the ABS relay has contact problems, or the 140 bar pressure switch isn't working.
However, if the the 100 bar switch is faulty, the pump can do what it's supposed to do, and you'll get the warning lights without there being a pressure problem.
If the lights come on while driving around, try to get the car to a safe place, and with everything running, open the hood. Where is the brake fluid level in the reservoir? If it is near or at the FULL WITH CHARGED ACCUMULATOR line, then the ABS pump is doing it's job, and there is a problem with the low (100) bar pressure switch. If the level is well ABOVE the FULL line, then the ABS pump hasn't been running. If the level is above the line, hit the brakes a few times and see if the pump turns on; if it does, then the problem is the low (100 bar) pressure switch. That's just to cover the case where the pressure was just above 140 bar, so the pump wouldn't normally come on.
If the pump isn't running, then it's time to check the 140 bar pressure switch, ABS pump relay, and ABS pump. It is possible for the contacts on the relay to carbon up - things work fine when cold, but as the system runs, the carbon on the contacts warms up and limits current to the pump. Eventually the pump doesn't get enough current to run. However, if you pull the connector off the pump and measure it, you see 12 volts, because the voltmeter takes a millionth of the current the pump requires. Or eveything looks good when cold.
posted by 192.249....
, Thu, 4 Aug 2005 08:57:20, Thu, 4 Aug 2005 09:54:19 <-- Viewing This Message, Thu, 4 Aug 2005 12:46:59
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
