Relay Question

[Drey]

Is there anyway to test a relay? I think I got a bad one.

I bought a set of two Hella driving lights for the K5. Got them all mounted up and the wireing all ran. I tested all my grounds with a light and I have 12 volts from the bolt on the firewall running to relay but I can get the lights to kick on.

 

[dremu]

Note that the square Bosch-type relays have a couple of different pinouts, so don't assume that you can wire them by position. Hopefully yours have markings on the side to determine which spade is #87 and which is ... uh, whatever the other numbers are =))

You'd need an ohm-meter to test them ... could do it with a test light if they're only 4-pin, i.e. SPST, but it's better with a meter.

One set of pins will be about 70 ohms, that's the coil (goes to ground and to the switch that turns the thing on and off). If there's four pin on the relay, the other set of pins should be open; if it's five, of the other three, two should be shorted together (the normally closed circuit, 0 ohms), and the third should be open (this is the normally open circuit.)

But, check the wiring numbers.

-- A

 

[Drey]

The Hella kit came with a plug that just goes onto the relay...so by rights I shouldnt have the wiring wront but Ill double check it.

 

[BobK]

Terminal 87 is the output terminal (goes to whatever you want to power) 87a it HOT when the relay is not triggered.
You can ignore the "87-not used" in my pic. I snapped this pic for something else. All the other terminal labels are correct.

 

[BobK]

So 87 should be connected to the lights
30 to your power source.
85 to ground.
86 is the trigger to turn on the relay.
86 is usually the switch.

 

[dremu]

The Hella kit came with a plug that just goes onto the relay...so by rights I shouldnt have the wiring wront but Ill double check it.

Eh. Then yeah, it should magically work. Those Hella relay sockets sometiems have a fuseholder on 'em, make sure the fuse is good and tight.

You can test for 12V at the lights with your test light, and you can also test for 12V at the output of the relay (#87, by the looks. I can never remember.) Work your way back; if there's no juice at the lights, see if there's juice at the relay output, if not there then make sure there is on the 86 terminal from the switch, etc.

Note that I *loathe* test lights as they don't detect low-voltage conditions terribly well, can't be used to test open-ground circuits or resistance without creativity, etc etc. Even a $10 cheapo voltmeter is infinitely more accurate and useful.

-- A