LT Texan

Here's one I never got before.

The central warning system came on, flashing lights and all, for Brake Pressure.

I figured it was a misreading, and would clear up with a quick on/off.

It didn't.

Brake fluid is fine.

Brake pedal pressure is fine.

Brakes stop me fine.

Not sure where to look for this one.

Any suggestions?

The owner's manual says "pull over, stop the engine and remedy the problem."

Thanks....

dr bob

There are two pressure switches on the master cylinder. One for each diagonal brake circuit (RF/LR and LF/RR) on the early cars. The two pressure switches need to be actuated concurrently; if only one is activated, the dash warning light comes on when you push on the brake pedal. It's telling you that one circuit is not holding pressure the same as the other. Might be that there is a leak in one side, might be that one of the circuits in the master cylinder is leaking by. It also might be that one of the switches has failed, or the wiring to one of the switches has high resistance.

The switches are known to cause problems when they get old, so my first step after checking fluid levels and the wiring on the MC would be to disconnect the battery for a few minutes to reset the alarm. If it comes back when you push on the brake, next step would be to replace those two switches. The switches are common to several VW series, probably starting with 1970-ish Beetles. There are some cheap aftermarket switches that are not reliable, so it makes sense to find good ones. 928 International has them local to me, and I'm sure the other guys have them too. Note the wire positions on the switches when you remove them, and replace them the same way when you install the new switches. Change them in pairs, BTW.

LT Texan

Thanks Dr Bob. Always informed advice.

Should have replaced these when the engine was out a few weeks ago!

Live and learn.

jpitman2

BTDT. The switches require a 24mm wrench. DO NOT OVERTIGHTEN! it can crack the m/cyl. Replace both together. Takes some patience and small fingers to get the connectors back onto the switch contacts. When i did mine, I sealed the reservoir lid with gladwrap or similar to reduce fluid loss, did 1 switch at a time, removed the lid seal, topped it up, let it sit over night, and did not neet to bleed the system. Mine also had the leads for one switch very tightly twisted up, as though the switch had been fitted and tightened with the lead connected - this could affect the the warning light also, so check that the wiring under the connector hood is in good condition also.
jp 83 Euro S AT 53k.