Relays

Wig

Does anyone here understand relays?

When I look at relays they all have similar names for their terminals but the terminal no.s seem to be in different positions in the circuit. If you look at the bottom of the relay where the pins come out sometime the pin at the top might be 30 on another relay the same pin position is 86. the other pin positions seem to be consistent i.e. the 87 is always at the bottom the 85 is always on the left the 87a is always in the centre (if present).

If the pin positions are different then they are obviously not interchangeable

But on my car I have a fuel pump relay 12v 30A which is purple and made by Bosch for GM, Next to it in the fuse box is a green (possibly made by Bosch) GM -12V 30A relay the pin positions are exactly the same and the circuit diagram is the same. So one would think that the green and the purple relays are interchangeable but if that is the case why are they different colours and why did the factory not put 2 identical purple relays instead of 1 purple 1 green.?

I have a relay Green, with white base 12V
Hella 4RD 003 520-25

pin positions: ....|30
............... |85__87a |86
.....................__87

Pins in use all of them except 87a

I'd like to test it, any way I can do that?

Failing that I'd like a new one and wondering what type of relay it is so that I can buy a new one maybe from a cheaper manufacturer but I don't know if the 4RD is the generic type?

Nodding_Donkey

The different colours are likely to denote different maximum amperage. Does the Hella one have a circuit diagram on it?. If it does you need to apply 12v to the switch terminals which should give continuity between the other two.

Iceweasel

This should help you:

http://www.autoshop101.com/forms/hweb2.pdf

Pages 8 & 9

Wig

The circuit diagram for the Hella is almost exactly the same as this one except on mine it says 86+ and there is a diode between 85--->|---86 across the box with the diagonal line (is that a symbol for an electro magnetic coil?)
http://www.thetoolboxshop.com/0-728-12-durite-12v-20a-30a-mini-changeover-relay-2141.html


Regarding the two identical relays on the car, they are identical circuits and pins and both say 12V 30A so they are both 30amps but they are different colours and the relay board has a purple outline where the purple one goes and a green outline where the green one goes......... weird.


Thanks for the link....

So to test it I should:
Step1 put 12V across 85 - 86 with the +ve on 86 (I should hear a click)
Step 2 with 'Step 1' still connected, connect the 12V +ve also to 87
and I should measure 12V on the meter at pin 30 ,,, if it is working

And 87 - 30 should be open circuit but when 12V applied to 85-86, 87 - 30 will be closed circuit.

I'll try and do this.

Anyone confirm my method is correct?

Joe_Horner

The colour coding will be just to help identify the circuit, the same as all that "identical spec but different colour" wire that they use. Even my favourite old 1970s cars can be nasty to fault-find electrics on without the colour coding, on a modern car it'd be all but impossible!

Quietmanc

Wig wrote: »

The circuit diagram for the Hella is almost exactly the same as this one except on mine it says 86+ and there is a diode between 85--->|---86 across the box with the diagonal line (is that a symbol for an electro magnetic coil?)
http://www.thetoolboxshop.com/0-728-12-durite-12v-20a-30a-mini-changeover-relay-2141.html

Do not ever swap a relay with a diode across the coil for one that hasn't.


So to test it I should:
Step1 put 12V across 85 - 86 with the +ve on 86 (I should hear a click)
Step 2 with 'Step 1' still connected, connect the 12V +ve also to 87
and I should measure 12V on the meter at pin 30 ,,, if it is working

And 87 - 30 should be open circuit but when 12V applied to 85-86, 87 - 30 will be closed circuit.

I'll try and do this.

Anyone confirm my method is correct?

That method looks ok. 85 and 86 polarities may sometimes be changed over if no quenching diode fitted. 30 is normally regarded as the +ve switched input.

ohreally

Sorry, I thought you wanted to test a relay.