i'm setting up a relay wiring system for my 245 h/lights.

i'm using the newer bosch relays p/n -101, which has terms 87 & 87a.

i have 4 relays, one/each beam.

when wiring, should i splice together 87 & 87a wiring or just ignore 87a altogether and just use term 87?

thanks again brixsters!

regards,
byron golden
bc1_2002
near houston, tx
86 245, 1 owner, 240k+ mi, purrs beautifully
working on a 300k badge

a relay with 87 & 87a terminals is a single pole, double throw relay.

When trigger voltage is applied, the relay closes 30 & 87.

When no trigger voltage is present, the relay closes 30 & 87a

For headlights, ignore 87a. Better yet, if the relay is in any way exposed, and you're using terminals rather than sockets, try to cover 87a so it can't possibly make contact with anything.

Evan, thanks for clearing that up & it makes sense--i never thought about covering 87a.

great and much, much help. i'm off to walmart for some 12 g wire.

regards,
byron

The 87a terminal is connected directly to the input(30), whenever the relay is "off". If you are just using the relay as a switch to carry power to the headlights, don't connect anything to 87a. In fact, it would be a good idea to insulate it with some shrink tubing, etc. Use terminal 87 as the output to the lights.

Relays with a terminal 87b are different - that terminal is connected to 87 so they are both live (and both dead) together.

I'd say that 4 relays is a bit of overkill. The relays have a capacity of 30 amps - some Bosch models it's 40 - and even if you have a 4-headlight setup, the high beams draw only about 17amps. One relay for lows and one for highs would be plenty.

Note that using relays eliminates the bulb-out warning function for the low beams so you need to check your lights frequently.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)

thanks bob, good advice on insulating 87a & will do. seen your words of volvo wisdom many times.

regards,
byron