Interesting. Gives some info about the pins (30, 87, and 87a etc).

Relay Basics
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Norm Cook Vancouver BC; 1989 745T 202,000KM

Some additional info on using relays, especially Bosch 5-pin:

http://www.bcae1.com/
and
http://www.underthedash.com/relayindex.html

Information on ISO numbers, the numbers that are on the terminals of Bosch relays and all over our wiring diagrams. What exactly do they mean? Here:

http://www.isham-research.com/quattro/wiring/Typ85/terminals.html
and also
http://www.356registry.org/Tech/electrical_codes.html

More application info for aftermarket relays, and a source of VERY cheap relays:

http://www.hella.com/produktion/HellaPortal/WebSite/Internet_usa/ProductsServices/On_Line_Catalogs/Products_Accessories/Products_Accessories.jsp
cheap relays of unknown provenance can be found at
http://www.hosfelt.com/en-us/dept_111.html

I'm not savvy enough to make hyperlinks...copy, paste and enjoy.
The last time I went to a store to buy an OD relay, I brought my old one and showed it to the gal behind the counter. "This isn't a Bosch relay, it's a Hella!" she said.
"I bet it's Hella expensive!" I answered.
I was right.

Doesn't seem to have much of a clue, actually.
The diode is to prevent induced reverse voltage from wasting transisor drivers, for instance.

I wouldn't say he doesn't have a clue. Maybe some of his technical points are incorrect--I don't know since this is mostly new info to me.

The article was titled Relay Basics. Just the info about the pins and their functions were of use to me.
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Norm Cook Vancouver BC; 1989 745T 204,000KM

Nice find—and basically OK. But seems to imply that "the Bosch 5-pin relay" is always configured like his example (double-throw with one Normally Closed point and one Normally Open). There are other configurations too.

Fortunately most Bosch relays have their layout shown in a picture on the outside of the case, as do a few of the other manufacturers.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.