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Username Post: Want to send neg when lose power...relay        (Topic#356217)
56_Kruiser 
Valued Contributor
Posts: 2815
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
04-29-19 09:59 AM - Post#2765286    

I want to have a relay that when a particular circuit loses power that it sends a negative to the output wire. I was told to wire it like this:

85 and 87a -> Ground

86 -> Power (NOTE: I am using this terminal as the one that I want to monitor. So if it loses power, the end result is that the relay has no power on any ports)

30 -> Output (I have wired this to the negative side of an indicator. So when I lose power, which is the power on 86, then a gnd gets sent here)

I find it to not be working.

Have I misunderstood the instructions I received?

Any help appreciated very much.


1956 Chevy
Vid of 61
61 Chevy


 




gchemist 
Senior Chevytalk Moderator
Posts: 24690
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
04-29-19 10:26 AM - Post#2765291    
    In response to 56_Kruiser

Ok, I'm confused.
Wouldn't you need two relays?

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
acardon 
Ultra Senior Member
Posts: 11181
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-29-19 11:37 AM - Post#2765294    
    In response to 56_Kruiser

Is the indicator using the same power as 86?

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
gchemist 
Senior Chevytalk Moderator
Posts: 24690
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
04-29-19 01:41 PM - Post#2765302    
    In response to acardon

For my 165 amp alternator, I have a dash light in the circuit. It lights up when the alternator is not charging. It's the exciting wire to get it started. Once the alternator kicks on to charge, the light turns off.

Are you trying something similar?

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
56_Kruiser 
Valued Contributor
Posts: 2815
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
04-29-19 01:59 PM - Post#2765304    
    In response to gchemist

  • gchemist Said:
Ok, I'm confused.
Wouldn't you need two relays?



I don't know...you tell me. I had posted on the12volt.com forum, and was provided with that method.

The thing that I have felt suspicious of this method is that the relay ends up with no power. But I thought, well, it needs to just send a ground...so maybe no power needed...maybe the power on 86 is what is keeping 87a from sending the ground out 30.

  • acardon Said:
Is the indicator using the same power as 86?



No.

  • gchemist Said:
For my 165 amp alternator, I have a dash light in the circuit. It lights up when the alternator is not charging. It's the exciting wire to get it started. Once the alternator kicks on to charge, the light turns off.

Are you trying something similar?



Yes. Here's what I'm trying to do:

I have had fuse blow and end up with no brake lights in the past. So, I want to know if the fuse to the brake switch blows.

I have a Dakota Digital dash in my '61, and it has a port on the controller to put a negative to that turns on the brake warning indicator. The intention of the light was for the emergency brake...but I don't have a switch on it, and figured this would be a great use for that.

[EDIT]
I find that the relay is warm. I'm sure it is hot all the time, and draining on battery. I definitely need a different solution...maybe 2 relays.


1956 Chevy
Vid of 61
61 Chevy


Edited by 56_Kruiser on 04-29-19 03:04 PM. Reason for edit: No reason given.

 
acardon 
Ultra Senior Member
Posts: 11181
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-29-19 03:08 PM - Post#2765310    
    In response to 56_Kruiser

  • Quote:
85 and 87a -> Ground

86 -> Power

30 -> Output



You realize that with the brake switch (constant power) connected to 86 and 85 grounded, the relay will stay energized 24/7 and run the battery down.
That said, it looks like it should work.
Does the indicator light come on when 30 is grounded? Check for continuity to ground on 30 with the brake fuse pulled.
86 is connected to the fuse side of the brake switch?
I missed your edit.



Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


Edited by acardon on 04-29-19 03:12 PM. Reason for edit: No reason given.

 
56_Kruiser 
Valued Contributor
Posts: 2815
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
04-29-19 05:38 PM - Post#2765336    
    In response to acardon

Well, update....

I find it working although I think intermittently. I must have a loose/poorly made connection. I can chase that.

But, I am left with want of a way to do this without a constantly hot relay using up battery all the time. Is it possible?

1956 Chevy
Vid of 61
61 Chevy


 
acardon 
Ultra Senior Member
Posts: 11181
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-29-19 06:53 PM - Post#2765342    
    In response to 56_Kruiser

As mentioned, a second relay to provide a ground to 85 of the first relay.
Second relay:
85 to switched power
86 to ground
30 to 85 of 1st relay
87 to ground.

This will keep the 1st relay from energizing until the key is turned on, then both relays will energize. When 86 of the 1st relay looses power, 30 will go to ground and turn on the indicator light.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
56_Kruiser 
Valued Contributor
Posts: 2815
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
04-29-19 07:13 PM - Post#2765343    
    In response to acardon

@acardon...thanks! You've brought lots of answers to me, and others too. I really appreciate it.

I'll introduce another relay. (I have quite a few in that car).

1956 Chevy
Vid of 61
61 Chevy


 
65_Impala 
Very Senior Member
Posts: 4195

Reg: 12-29-02
05-02-19 09:58 AM - Post#2765552    
    In response to 56_Kruiser

Move 85 to another constant power source and ground 87 instead of 87a. Then, the indicator will come on when the fuse is blown and the brake pedal is pressed - the relay coil will be grounded by the brake lights when the brake pedal is pressed. It's a one relay solution and the relay is only energized when the pedal is pressed while the fuse is blown.




 
56_Kruiser 
Valued Contributor
Posts: 2815
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
05-07-19 05:50 AM - Post#2765872    
    In response to 65_Impala

Thanks! Done...

1956 Chevy
Vid of 61
61 Chevy


 
gchemist 
Senior Chevytalk Moderator
Posts: 24690
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
05-07-19 08:08 AM - Post#2765879    
    In response to 56_Kruiser

So you used only one relay? Or two?

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
bobb 
Super Senior Member
Posts: 5411
bobb
Loc: paradise
Reg: 09-05-03
05-08-19 10:34 PM - Post#2765993    
    In response to gchemist

whynot just use a circuit breaker?

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
WagonCrazy 
"12th Year" Platinum Supporting Member
Posts: 3155
WagonCrazy
Loc: So Cal
Reg: 06-07-05
05-11-19 06:39 AM - Post#2766166    
    In response to bobb

Here's a great resource on all kinds of relay wiring diagrams, for many different automotive scenarios...

the12volt

57 Nomad -LS1 with C4 suspension
59 Apache Fleetside Shortbed BigWindow



 




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