dshepp806

Anyone have the schematic for the rear defroster relay circuit (INTERNAL, not the Bentley wiring)...? I've the damned thing but cannot find it today......

Thanks,

Doyle

dshepp806

To cold to work outside on such a simple circuit...my bench pwr supply crapped out or we'd be fixing this quickly. There are 3 transistors on this board and I'm suspecting one has failed. It looks (although I haven't yet drawn out the schematic---easy to do) that one of these transistors drives out a ground signal (probably a common emitter topo) for the opposite side of coil#2 , then I'd see 12 volts at 87a, as required (assuming relay is functional). No time to apply ground internally to the proper side of coil #2 to check coil functionality (or measure for ground there) but will do that, as well. Hopefully warmer this week and I can further the T/Shooting. WIll post accordingly.......

I'll keep looking for the schematic...I've got it somewhere on 3 servers............

Best,

Doyle

Ed Hughes

Doyle, I've got my Porsche factory manuals on a shelf over my head. There are several pages of 11 X 17 schematics....date is '86, but I'd assume '89 would be the same. Let me peruse the diagrams and see if there is an 8 1/2 X 11 section or two I can scan....

Ed Hughes

I got it....do you just need the schematic for the relay? There is one section that has it, the switch, the mirror component, etc......but do you need to trace it back to anywhere else?

dshepp806

No need to trace outside of the relay box, for now, as I feel the failure to be internal to the relay (a component).

I need the relay assembly schematic for the internals (Showing the circuit ITSELF,..with the transistors (3),..resistors, cap, variable resistor and diodes, etc....not "pics of")...no block diagram stuff,..or interconnectivity stuff (I have all of that)....

I want to study how relay number 2 is fired IN THE CIRCUIT..

I'm a "component-level" kinda guy...........

AS ALWAYS: Thanks for your help, ED!!!!!!!!!!!!!!

Doyle

Ed Hughes

I can scan and e-mail the pdf...my guess is it will be too big to post, but I can see what it ends up as. It's as detailed as Porsche published.

Ed Hughes

Yep, they come in at about 600k...pm me your e-mail and I can send to you. I scanned the Sheet 4 Schematic in 3 pages.

dshepp806

PM sent, my good man.

Another IOU......THANKS!!! ...(as I really didn't want to redraw this minicircuit,..AGAIN,.it was SO COLD out that I now realize I could , at least, be getting the transistor part numbers down and cross-referencing for data's sake...I'll keep you guys updated..

looking for your tx', Ed....

BIG THANKS!

Doyle



Doyle

Ed Hughes

You've got mail!

dshepp806

Ed,

Got the email. I appreciate the effort,..this was a factory rendition
In any case,..still not what I'm after....you will notice on attachment #1 (that shows the relay box in question) sshows ONLY a single transistor symbol,..and NO other components,..that is, it's a block diagram, .....I'm looking for the circuit,...i.e., how the following is laid out "electronically ,..that is,..a schematic.....

I'm still looking for this print,.........(argh)


Thanks again, Ed.

Doyle

Ed Hughes

I'll look at the other schematics, and see if it zeroes in any more...

dshepp806

BTW,..that's a shadow (for sure, under relay #1 (above the B21/LL) )No burn whatsoever....The output tabs have been burnished, coated and solder reflowed (underneath). Found the left bottom tab a bit loose....now tight.

Think I'll just draw this thing out...

Doyle

dshepp806

Some more activity on PP,...(data)..

http://forums.pelicanparts.com/porsc...defroster.html


Doyle'

User 4221

Good luck finding the schematic on this one. That is probably an internal document and would be very hard to get outside the company.

When you get this sorted out, I'd like to understand what you find. Especially with the timing circuit.

My money is on a failed relay as the contact material from the '80s was junk.... As we all know.... *cough-dme-cough*.

dshepp806

We'll see. Like I mentioned, I'll draw this puppy out (just NOT much there!) and report back,..this print exists somewhere as I've seen it before (just like other stuff such as the DME, heating relay, etc.). I've still one server to search on,..one day, I'll get organized............

A simple manual engagement of the relay will tell me if the unit's working or not,..so,...SOON.!!!!!!!

..if that be the case, it will be time to source a relay.....still WAY to early to tell...if manual engagement doesn't provide the intended results, her contacts will get a good burnishing (as will relay #1, BTW) then I'll have another go. Otherwise, time for bright magnification and an ohmeter to inpect those tiny coil windings [reminds me of working with guitar windings on pickups.....],..a simple ohmage test will tell me about the coil windings,...why transistors to fire these coils? (of course, assuming this to be the circuit's case.....AGAIN, I've NOT th circuit's print!!!!!!

I'm looking for Loren's input, here.

Still work, to do.

Best,

Doyle