Electrical Problems

[rcecale]

Driving home from work today, a friendly motorist pulls up alongside me and motions me to roll my window down. when I did, he indly informed me that my brake lights weren't working. RATS!!!

Get home, back the car up to the garage and position a mirror so i could have a look, and sure enough...nothing!

Jumped under the bonnet to have a look at the fusebox. Nope, that's not the culprit. The fuse was intact and fully operational.

I'm no electrician, but I sometimes can spell AC correctly. Should I have a look at one of the relays or something? I pulled them all out and reseated them, but still no brake lights.

Also, I think I may have jacked up my Windshield Wiper Control Switch. I pulled the steering a few days ago to straighten it out and put it back without issue. From that point on, whenever I start the car, the wipers turn on. The OFF position acts like the DELAY position. they will not turn off. The other two positions work normally (regular and high).

Bad switch, a short somewhere?

Randy

[Rot 911]

George Bush says it is probably your brake light switches on the master cylinder. There are two of them. Replace both. If you depress and hold down the brake pedal just and inch or so you won't even lose any brake fluid.

[rcecale]

Well, if George says it's so, it must be!

Just trying to clarify the orientation of this pic now. Is the "Forward" indication correct?

If so, it looks like there is some duct work that needs to come off in order to access the switches. Looks like it could be a PITA job, but one that needs to be done, I suppose.

Thanks Kurt!

Randy

[Rot 911]

Yeah I do believe some ductwork removal is required to replace the rear switch.

[rcecale]

Found this pic in the tech article about replacing the master cylinder. Explains the location pretty clearly.



Looks like I have another project for this weekend.

Randy

[bigchillcar]

often it's poor contact in the sockets for the bulbs..grappled with this intermittent gremlin for 7 years with my '74. it's worth a jiggle or two with someone holding the brake pedal down or do like me and use a wooden stick to hold the brake pedal down when there's no help around..

[rcecale]

Thanks, Ryan! I can try that before I leave for work in the morning, and still be prepared to swap out the switches this weekend, if needed.

Randy

[bigchillcar]

yeah, rear lights in these cars, especially the earlier ones, were poorly thought out..marginal engineering. wouldn't be surprised if jiggling them didn't work. only thing is you report that it's both of them..that would be far more rare. let us know what happens.

[rcecale]

Tried removing and replacing the bulbs this morning but still no joy. Brake lights are nowhere to be seen.

When I got home from work this evening I went in search of the switches on the Master Brake Cylinder. Got eyes and hands on both of them and discovered they were both the two-prong variety. Broke them loose, just to make the actual fix a lot quicker tomorrow, if I can find them locally.

Will see, tomorrow, if I can, and if not, will be happy to purchase them from our host.

Quick question though...what are the chances that BOTH switches are bad?

Randy

[bigchillcar]

sorry my fix didn't work, but agree the odds seem slim for both switches to fail at same time..wondering about a possible break in a common wire to the brakes. i might be checking a wiring diagram. any recent work on the car? in the rear? any idea how long they've been out of service?

[Goth]

"Also, I think I may have jacked up my Windshield Wiper Control Switch. I pulled the steering a few days ago to straighten it out and put it back without issue. From that point on, whenever I start the car, the wipers turn on. The OFF position acts like the DELAY position. they will not turn off. The other two positions work normally (regular and high)."

I did the same thing: Fixed turn signal switch & put wheel on... wheel crooked. Removed & put wheel on straight...Wipers won't shut off unless I hold the lever forward or was it backward (can't remember). Okay..Fix one break two.

Take the cover off & look at how the wiper switch operates. You will see that when you move the lever, it makes some contacts close while others may open. The contacts are pretty easy to spot and adjust, as they are like the ones you would find in many relays (looks like point type on flexible copper arm). You can bend the copper arm so the contact is in the correct position.

Good Luck! .

[rcecale]

Thanks, Doug! I'll prolly tear into that later this afternoon. Sounds like an easy enough fix.

As for the brake lights, the Pressure Switches did the trick.

Not sure if one, or both of them were bad, but they were both replaced. Step on the brake pedal and the lights come on. Simple enough fix!

Found some other threads on this same topic and they all seemed to point to the Master Brake Cylinder Pressure Switches. There were even a few questions asked of where these switches were located so I took a couple of pics to help explain.





Thanks for all the help, everyone!

Randy

[bigchillcar]

randy..hard to tell for sure from the pics, but do the replacements screw into the brake master..and then the wired plug ends connect to those?

[HelmetHead]

rcecale.... Just a thought...but i'm not sure if this would cause any sort of damage to the wiring or brake switches...I wouldn't think it would..they are contact switches open or closed right?

how about a small 2"-3" jumper wire to touch the contacts together on each of the pressure switches to see if those are infact the problem...if the lights don't come on still..it might eliminate the need to source/replace the switches...

seems highly unlikely that both pressure switches would go out at once.

Good luck.
HelmetHead

[rcecale]

Ryan,

Here's a better (closer) shot of the switch, with the electrical connector unplugged.



You are correct in that the switch (both of them) screw directly into the master cyliinder. A 22mm Deep-well socket will allow the best access, especially for the rear switch. The tool shop was out of 22mm sockets, so I picked up a deep-well 7/8", which worked just as well.

On the rear switch, I used the deepwell socket, combined with a universal, then a 6 inch extension. If you stay low with the socket, you can get really good access to it.



Helmethead,

For the price (less than $10 per), I just went ahead and purchased both switches and replaced them both. Maybe if I didn't have the car sitting in the direct sunlight, making me feel like I was working in an oven, I might have taken my time and narrowed down which one failed. But, since it takes more effort to actually get access to the switches, than to change them out, I figured, wth?

I agree with you though, I think the likelyhood of both of them failing at the same time is not that much at all.

Randy

edit: Found this thread and am asking about the wipers here as well...
Click here.

[bigchillcar]

thanks for the closeup, randy. glad the fix worked! don't know if my '90 964 uses the same switches as your '86 though.

[rcecale]

Ryan,

This parts diagram says there aren't any switches on your Master Brake Cylinder.

According to this link, it's on your pedal cluster.

Randy

[bigchillcar]

thanks, randy..good to know for the future!