A/C Clutch Relay Questons

[Mike Arman]

>
>In
>searching the archives, the likely cause was a shorted diode that connnects
>between #30 and #87 on the relay. Sure enough, there was continuity 
>between those
>two pins, and when I cut one of the diode leads, the relay acted "normally"
>being open in the normal condition and continuity between the two pins when I
>manually closed the relay

>So far, so good. One of the writeups mentioned replacing the defective diode
>with a Radio Shack 50v 2Amp diode. That would be fine, except my radio shack
>only had 1 amp and 3 amp diodes from which to choose. So, I got one of each.
>The question is, which one to use? I am thinking the 3 amp, but I will defer
>to those more knowledgeable on the topic. Also, the diode is directional.
>What is the proper orientation?

Use the three amp diode, it will be fine.

Look for a white band on the diode itself. That indicates the + end. Match 
the old one. RS diodes are marked, the OEM diode may have a different 
marking, if it has an arrow, the arrow points to the plus end. There may 
also be a "+" symbol printed on the PC board at one of the holes for the 
diode wires.



>This will be the first time doing a hack job on a circuit board, although I
>have done the basic soldering for universal oxygen sensors many, many times.
>Any tips for soldering/unsoldering?

Use a smaller iron, remember PC boards can't take much heat without coming 
apart. Fresh ROSIN CORE solder (electronics solder, not plumbing solder), 
keep the iron clean and tinned. RS sells "solder wick" which is a braided 
copper "tape" which pulls off the old solder, again, be careful of 
overheating the board.

"Flicking" the relay will also fling off any excess melted solder - be 
aware that your cat will be *highly* upset if you splash drops of molten on 
her, so be aware of which direction you're doing this in, and what is over 
there.

You can buy a "solder sucker" at RS, if you're only doing this one job, 
don't bother.

And of course, you have to get it hot enough to make a proper solder joint 
- if your solder joint is dull, blobby and has little pinholes in it, 
that's a cold solder joint, reheat and try again. The solder joint should 
be shiny and make a smooth fillet along the wire. Doesn't take much solder, 
either. This isn't glue, and more isn't better.

This takes a little practice, not too much, and you might want to try it 
out on a junk PC board from a dead relay or transistor radio or something.

The whole shebang won't take more than a minute or two.


>Thanks,
>-- Tom


Best Regards,
Mike Arman