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Username Post: Want to send neg when lose power...relay        (Topic#356217)
56_Kruiser 
Valued Contributor
Posts: 2843
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: 24839
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: 11261
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: 24839
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: 2843
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: 11261
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: 2843
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: 11261
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: 2843
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: 4227

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: 2843
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: 24839
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: 5447
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: 3172
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



 
56_Kruiser 
Valued Contributor
Posts: 2843
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
06-09-19 07:40 PM - Post#2768076    
    In response to gchemist

  • gchemist Said:
So you used only one relay? Or two?



I went with 1 relay:


  • bobb Said:
why not just use a circuit breaker?



Because it was blowing fairly often, and I wanted a fix rather than a work-a-round.

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

the12volt



Thanks. That is a great resource, and I do use them. In fact, what I started the thread with was what I got from there, but was getting no replies when it didn't work. Turned out I get better info here, this time anyway.

They gave me a great (complicated, at least for me) resolution a while back on how to change the polarity for a cruise control switch on the column which at the time did not come in the polarity I needed.



1956 Chevy
Vid of 61
61 Chevy


 
56_Kruiser 
Valued Contributor
Posts: 2843
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
06-11-19 08:03 AM - Post#2768213    
    In response to 56_Kruiser

Well, turns out it is not working
I've been away from the project for a while. Now that I'm back, I find it is not working.

Reminder of goal:
I want to send a negative signal when power goes off on brake wire (ie. fuse blows on brakes). Also, accomplish this w/o having the relay active all the time pulling juice from battery.

Currently wired like this

30 - Wired to brake warning light in dash, needs negative
85 - Hot
86 - Wire feeding hot side of brake switch - When this loses power I waant the negative sent to 30
87 - Ground
87a - Empty

NOTE: When I had initially tested I had left the gnd wire on 87a. Turns out the warning light was on all the time, and the info above had said to move that to 87. Instead I had put 87 on a ground, but forgot to pull the gnd from 87a. It is now corrected.

BUT...it is not working. When I pull the fuse to the brakes the warning light does not come on.

So have I misunderstood how to wire this?

Suggestions?

1956 Chevy
Vid of 61
61 Chevy


Edited by 56_Kruiser on 06-11-19 08:04 AM. Reason for edit: No reason given.

 
56_Kruiser 
Valued Contributor
Posts: 2843
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
06-11-19 02:49 PM - Post#2768245    
    In response to 56_Kruiser

I just realized something else. The suggestion made by 65_Impala will only turn on the light when I press the brake. That is not really what I'm looking for. I likely will be watching the road and not looking at the dash when I am pressing the brake, and not see the indicator. Given that, I should stop chasing the 1 relay solution.

So, I need to drop back and do the original wiring on the 1st relay, and then wire a second one as acardon suggested.

That leaves this:

Relay 1
87a -> Ground
85-> 30 on relay 2
86 -> Power (Same power supplying the brake
switch)
30 -> Output (to negative required port on dash
light)

Relay 2
85 to switched power
86 to ground
30 to 85 of 1st relay
87 to ground.



1956 Chevy
Vid of 61
61 Chevy


Edited by 56_Kruiser on 06-12-19 06:47 AM. Reason for edit: No reason given.

 
56_Kruiser 
Valued Contributor
Posts: 2843
56_Kruiser
Loc: St. Augustine, Fl
Reg: 09-23-05
06-12-19 06:52 AM - Post#2768297    
    In response to 56_Kruiser

Success!

Wired per the above post, derived from earlier posts.

I'm sure I knew this long ago, but it was driven home here (hopefully learned for real )...READ AND CONCENTRATE. Had I done that fully on the post about the way to use only 1 relay, I would have realized I needed to be pushing the brake pedal to have the warning light come on. I would have gone the 2 relay route in the first place.

Not to discount that suggestion (all help appreciated). But for me the constant on is what I was looking for.



1956 Chevy
Vid of 61
61 Chevy


 
WagonCrazy 
"12th Year" Platinum Supporting Member
Posts: 3172
WagonCrazy
Loc: So Cal
Reg: 06-07-05
06-18-19 08:13 AM - Post#2768748    
    In response to 56_Kruiser

Congrats Kruiser!

  • Quote:
I'm sure I knew this long ago, but it was driven home here (hopefully learned for real )...READ AND CONCENTRATE.



When it comes to wiring and wiring theory...definately have to shut out all other distractions and focus on what you are trying to accomplish, think it thru, etc. I find myself in the same wiring hell at times too. But its satisfying when you get it figured out. Builds confidence for the next wiring challenge.

Now get out there and drive that beautiful 56 vert.

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



 
Geoff 4 
Poster
Posts: 1

Reg: 07-08-19
07-13-19 02:34 AM - Post#2770574    
    In response to WagonCrazy

What am I missing? How is this going to find the cause of the brake light fuse blowing?



 
acardon 
Ultra Senior Member
Posts: 11261
acardon
Loc: DFW TEXAS
Reg: 03-25-05
07-13-19 02:02 PM - Post#2770618    
    In response to Geoff 4

  • Quote:
How is this going to find the cause of the brake light fuse blowing?



It won't find the cause of the blown fuse, it will tell you that the fuse has blown. Tri-5 chevy's were wired back in the day that several light circuits shared one fuse. Any one of the light circuits could blow the fuse, but since you don't know if the lights are working except at night, the indicator will warn you that the brake light isn't working.

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


 




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