Isolation switch... doesn't (now hellishly confused)

spandit · Post by **spandit** » Sun Jan 23, 2011 11:54 am

I was installing an override switch for my rear work/reversing lights. The switch I was using has an LED built in (which I was told was 12V only but actually seems to work fine with 24V). Despite having the cut-off switch to the "off" position, I found that the LED was lighting up, albeit very dim.

Some investigation followed which showed that there was a steady 1.6V between chassis and permanent live (measured at the hazard light fuse). Oddly, this rose to 3.5V when I pulled the fuse that powers the work lights so a bit confused as to what is going on.

To save my batteries running down, I have disconnected the earth cable at the rear battery, which proved there wasn't a mysterious battery hidden in the system somewhere!

The isolation switch isn't easy to access to check out the fault

edzz · Post by **edzz** » Sun Jan 23, 2011 12:41 pm

May be of help
http://www.sdp-pinzgauer.org/html/bypass_relay.html

Ed

spandit · Post by **spandit** » Sun Jan 23, 2011 12:53 pm

Just after I posted it I thought about the relay. I was washing the engine bay today so perhaps I've got moisture in it. I'll check it out as described in your link - thanks

spandit · Post by **spandit** » Sat Jan 29, 2011 5:53 am

Well, I took the panel off to access the cut-off switch and it seems to work OK, so swapped my attention to the relay. It didn't have continuity between pins 30 and 87 which implies it is cutting off correctly. However, there was open circuit between 85 and 86 which isn't correct.

Took the casing off and sure enough:

There is a break in the coil wire. Looks a bit difficult to solder as it's so thin so I'll replace the relay, I think. Doesn't explain why I was getting voltage leaking across the relay, though. I would've thought that it would have the opposite effect and not protect the engine in case of the main switch being turned off

spandit · Post by **spandit** » Sat Jan 29, 2011 2:45 pm

Turned my attention back to the cut-off switch and think it was suspect. Have replaced it with a newer one (standard car type) which fitted perfectly in it's place, albeit with M5 rather than M6 fittings. The keys are interchangeable too, which is nice.

Took the old one apart and gave it a clean - still not sure how it was leaking but on reassembly it seems to be working again. Odd.

cronapress · Post by **cronapress** » Sun Jan 30, 2011 3:05 am

Refurbing the cut-off switch is a very satisfying job ! I've done the grand total of TWO now ! Once you've uncrimped the tinwork, it's a straight forward job. Rewarding to get the copper contacts bright again. Dollops of good old Waxoyl in the vital bits. Peen the lip over again. Ding ding... away we go for another 30 odd years !!!

I Meggered the first one. Can't recall the readings, but it leaked a lot. Waterproof - they are not !

Mike

spandit · Post by **spandit** » Sun Jan 30, 2011 3:56 am

It's a Porsche 911 unit, like a lot of the things on the Pinz. I'll leave my modern one in for now but carry the original as a spare. I can always disconnect the battery at source should I need to