Wiring-what Does This Do?

Looks like a GM a/c compressor connector. Those were set up like that to reduce voltage spikes and backfeeding when the compressor clutch was engaged. Just so happens they were the same dimensionally for many other switches used in Jeeps, like backup light switches. I used one in the daughter’s ‘69 on her T-14 when I rebuilt it. I had to cut apart the connector and remove the diode or resistor, I forget which that one had. I think diode.

 

How are the switches failing? Internal leaks or corrosion on the points? I could see using the switch to signal a relay to reduce wear on the points. That would also prevent the back feed into the switch if used for towing.

 

The lights stop working...no contact in the switch. I have used Standard, Delco, and a "low pressure" switch from Painless Wiring. I think now I will cut this plug out and replace it with a standard one...see what happens.
I also flushed out the brake fluid today, in case there is debris in the system plugging up the switches (it looked pretty clean so I don't think it is an issue).

 

Suggest someone did this

 

Now that kind of looks like a diode (Doug's pic in post 18). The band would be on the green wire end.

Yes, that's right - same as what Nick suggests above. You got the commonly used name right. Shorts out the inductive spike from switching a motor or coil or such.

 

We had a recent thread about this. Hydraulic Brake Light Switch Failure - Again CJMark linked to this interesting post on a Volvo page - SW-EM Hydraulic Brake Light Switch Investigation

Yes, you could use a relay. The coil of a Bosch-type relay is about 150ma, while the bright filament of an 1157 is 21 watts => 1.6A for each bulb, so a considerable load reduction from the bulbs. The relay coil does have an inductance, so here a snubber would make sense, I'd think. Maybe not needed for such a small coil, but easy to include when you are adding the relay.

 

I’m pretty sure we could start a thread similar to the “What is this?” thread called “Why in the world would someone do this?”

Some of the crazy things I’ve seen in old jeeps over the years...

 

Yep Nick nailed it.

 

Do you guys think that could be causing my repeated switch failures? I don't see how but I'm no electricity expert....

 

In this article, SW-EM Hydraulic Brake Light Switch Investigation , it states that the current across the internal contacts causes arcing and failure. If you were to use a low voltage relay ,or even one with a full 12 vdc coil, and use the pressure switch to only fire the coil in the relay to power the full current of the brake lights the pressure switch last longer.

I would still just wire up a regular switch to run either the full current of the brake light off the brake pedal arm or to fire off the coil of a relay to do it. I was so irritated with the situation that I made sure to pick hanging pedals to eliminate the pressure switch amongst other reasons.

 

Just a couple of thoughts (take them for what they're worth!!)

You could go to LED brake/turn lamps to lower the current draw way down. If your brake lights and turn signals use the same lamp (pretty common), you'd need a mechanical flasher in place of the regular one to go LED (you can add a resistor instead but to me that defeats part of the advantage of having LED lamps). I've had a mechanical flasher in my Jeep for a long time, but still have the regular brake/turn lamps in it. For now. I plan to replace them in the near future. Note that with a regular flasher, if one of the regular lamps burns out, it will flash a lot faster than normal (letting you know there's a burned out lamp somewhere). You won't get that with regular lamps and a mechanical flasher. It will always operate at the same rate regardless.

 

If the switch contacts are arcing (if that's really the problem), I'd think you could put a capacitor or RC circuit across the switch contacts and prevent arcing that way. This slows the voltage rise/fall across the switch contacts. Supposedly Horowitz&Hill TAOE has a discussion of switching inductive loads which you can look at, or I will look when I get home. If you use a relay, you want a snubber across the relay coil, as shown here.



Here the DC load is the relay coil, and the switch is to the left. You can buy relays with diode snubbers built in - mind the polarity.