How to reset brake pressure warning switch? Options

[andreic]

I have a 1972 914 1.7L with the original master cylinder. After a lot of adventures with the brakes two years ago I replaced the front calipers and the brakes have been working great since then.

However about a year ago I noticed an intermittent clicking of one of the relays, like the one for the turn signals, just less frequent and less regular. It might click every few seconds. No light comes on the dash.

After a lot of diagnosing I traced it down to the brake pressure warning switch on the master cylinder. If I disconnect the line going to the switch, the clicking stops. My guess is that somehow the switch was left over in some intermediate stage where it is neither on (when it would turn the red warning light and blink vigorously) or off.

At the time I tried to clean off the gunk around it and to reset it. The cleaning seemed to help (it stopped clicking for a few months, but now it's come back) but I cannot for the life of me figure out what needs to be done to reset it. There is a little black button-like thing, between two copper vertical bars. There does not seem to be a way to push the button in any more.

Any suggestions short of replacing the switch? I don't want to have to deal with the hassle of needing to bleed all four brakes all over, etc.

Thanks.

[bdstone914]

Use a small wood dowel as a punch and tap on it. It should be flush with the switch surface.

[andreic]

Thanks! I will try that and let you know how it goes.

[andreic]

I took the big metal cover off now to try to tap on the switch, and I am more confused now. What I vaguely remembered as a small button is actually a big plastic vertical "bar" like separating the two electrical connectors. I attach a picture from the internet of a very similar looking switch.

Is the black plastic thing a cover that needs to be removed before I tap on the switch? Or is the black thing the switch itself that needs to be tapped down? Its bottom part appears to be flush with the body of the switch.

Thanks!

[andreic]

Bump. Bdstone914?

[914_teener]

Two things:

You may have reversed the leads....or...


The switch is old and the contacts have corroded and grounding the relay.


More than likely the later.


That circuit can have other reasons besides the MC indicator that will make the realy click. Is it the turn signal relay that is clicking?

[andreic]

I had not touched the leads before it started clicking; and the clicking is intermittent; I guess reversing the leads would give a permanent clicking.

The switch may indeed be old (and need to be replaced), but I wanted to reset it before replacing it. Trouble is, I still don't understand how to reset it.

What other causes can there be, besides the switch misbehaving, that could make the relay click intermittently? When I disconnect the leads the clicking stops.

[914_teener]

Some on 73 and earlier are not resetable.

There are more that several possibilities on the circuit. The German engineers were VERY efficient on the grounds.

Read:

http://www.914world.com/bbs2/index.php?sho...88745&st=20


Get out your DVM and start on the OHMS setting. Otherwise you'll be just quessing it's always the switch the MUST be faulty.


Keep us posted.

[trick-e]

I’ve a similar issue, for a ‘75, and have a question about this response:

‘That circuit can have other reasons besides the MC indicator that will make the realy click. Is it the turn signal relay that is clicking?’

For my issue, yes, it is the turn signal relay and brake indicator light that click/flash in time and at the same tempo as when a normal turn signal is engaged. Also, the turn signal indicator dash light no longer flashes when when engaging the signal lever.