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> Working with Relays, A little help understanding...
malaga_red75
post Jul 15 2009, 04:19 PM
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So I am using aftermarket relays for the fuel pump and the cooling fans on my subaru conversion, using the stock ECU. I have attached a picture of the relay diagram.

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So, there are two circuits, an 'inner' circuit and an 'outer' circuit. The outer circuit is only completed when the inner circuit's electromagnet is active.

It is currently wired like this: The 'inner circuit' receives a signal from the fuel pump pin on the ECU which goes into terminal 86 on the relay. (and here is where i think it has been wired wrong), coming out of terminal 85 the wire goes into the ECU into a 12 volt power connection. This is for the 'inner' circuit which should ignite the electromagnet. --- I THINK THIS IS WRONG. ---Shouldn't the wire coming out of terminal 85 go to a ground? thus completing the inner circuit and cause the magnet to attract the arm to complete the 'outer' circuit.

I hope that wasn't too confusing, let me know. Thanks a bunch!

-Peter
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underthetire
post Jul 15 2009, 04:21 PM
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QUOTE(malaga_red75 @ Jul 15 2009, 03:19 PM) *

So I am using aftermarket relays for the fuel pump and the cooling fans on my subaru conversion, using the stock ECU. I have attached a picture of the relay diagram.

Attached Image

So, there are two circuits, an 'inner' circuit and an 'outer' circuit. The outer circuit is only completed when the inner circuit's electromagnet is active.

It is currently wired like this: The 'inner circuit' receives a signal from the fuel pump pin on the ECU which goes into terminal 86 on the relay. (and here is where i think it has been wired wrong), coming out of terminal 85 the wire goes into the ECU into a 12 volt power connection. This is for the 'inner' circuit which should ignite the electromagnet. --- I THINK THIS IS WRONG. ---Shouldn't the wire coming out of terminal 85 go to a ground? thus completing the inner circuit and cause the magnet to attract the arm to complete the 'outer' circuit.

I hope that wasn't too confusing, let me know. Thanks a bunch!

-Peter




Not cornfusing. The ECU fuel pump output is a switched ground. So your set up sounds correct.
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malaga_red75
post Jul 15 2009, 08:37 PM
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Ok, so that leads to my next question, what would cause the fuel pump output signal not to switch?
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r_towle
post Jul 15 2009, 08:50 PM
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try reversing the way you have it wired to the relay..one side may be ground.

RIch
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budman5201
post Jul 15 2009, 08:56 PM
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QUOTE(r_towle @ Jul 15 2009, 07:50 PM) *

try reversing the way you have it wired to the relay..one side may be ground.

RIch


maybe something is backfeeding? Subaru Idle control units sometimes hold voltage and backfeed through the system.
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jt914-6
post Jul 15 2009, 08:59 PM
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Maybe this will help......

Attached Image
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r_towle
post Jul 15 2009, 09:01 PM
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so you wired it backwards.
85 is ground...not positive

Rich
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busmech
post Jul 15 2009, 09:49 PM
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85 and 86 does not matter which one is pos. and which is neg.
Most ecu circuits are outputing a ground to activate a relay, but some are bat. voltage. You need to find out what you have, conect it to 85 or 86 does not matter, and then the other one goes to a ground or batttery.
you should have 30 wired to battery, fuse protected of course, then 87 goes to the fuse pump
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mskala
post Jul 15 2009, 10:44 PM
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QUOTE(busmech @ Jul 15 2009, 11:49 PM) *

85 and 86 does not matter which one is pos. and which is neg. ...


Yes it matters, if you wire it opposite you will get the field reversed which will
keep the output from changing ever.
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busmech
post Jul 15 2009, 11:09 PM
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Here is a good explanation of the bosh relays
http://www.bcae1.com/relays.htm
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busmech
post Jul 15 2009, 11:13 PM
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Just above the animation there is a paragraph that says what i am saying.
I work on buses with relay logic that controls a lot of the functions, bosch style to 4 pole relays, time delay relays etc.
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busmech
post Jul 15 2009, 11:19 PM
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The only time that you need to have a certain polarity is when you use a supression diode, which the questioned relay does not have.
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malaga_red75
post Jul 16 2009, 01:59 AM
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QUOTE(budman5201 @ Jul 15 2009, 07:56 PM) *



maybe something is backfeeding? Subaru Idle control units sometimes hold voltage and backfeed through the system.



you mean the Idle air control valve? Also, Chriss, I sent you a PM.
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Tom
post Jul 16 2009, 08:20 AM
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Busmech, you are correct. Unless the relay has a protection diode to discharge the build up of voltage when the field collapses, then is does not matter which contact is + or ground for the coil circuit. It is just an electromagnet.
Tom
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Cap'n Krusty
post Jul 16 2009, 09:19 AM
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QUOTE(mskala @ Jul 15 2009, 09:44 PM) *

QUOTE(busmech @ Jul 15 2009, 11:49 PM) *

85 and 86 does not matter which one is pos. and which is neg. ...


Yes it matters, if you wire it opposite you will get the field reversed which will
keep the output from changing ever.


Generally speaking, you're wrong. The relay doesn't care about the polarity of 85 and 86. I'm sure there are diode protected ones out there, but I've yet to run across one. The Cap'n
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mskala
post Jul 16 2009, 11:04 AM
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QUOTE(Cap'n Krusty @ Jul 16 2009, 11:19 AM) *

QUOTE(mskala @ Jul 15 2009, 09:44 PM) *

QUOTE(busmech @ Jul 15 2009, 11:49 PM) *

85 and 86 does not matter which one is pos. and which is neg. ...


Yes it matters, if you wire it opposite you will get the field reversed which will
keep the output from changing ever.


Generally speaking, you're wrong. The relay doesn't care about the polarity of 85 and 86. I'm sure there are diode protected ones out there, but I've yet to run across one. The Cap'n


yes, since arm is not a magnet but just steel, I see it would not matter.
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rascobo
post Jul 16 2009, 12:22 PM
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QUOTE(busmech @ Jul 15 2009, 10:09 PM) *

Here is a good explanation of the bosh relays
http://www.bcae1.com/relays.htm


Sorry if I'm OT, but (IMG:style_emoticons/default/w00t.gif) wow what an great site!
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