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Why anti grind/starter cut relays drain batteries.

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Forum Name: Car Security and Convenience - Hot Topics
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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=126899
Printed Date: March 28, 2024 at 11:50 PM


Topic: Why anti grind/starter cut relays drain batteries.

Posted By: howie ll
Subject: Why anti grind/starter cut relays drain batteries.
Date Posted: April 09, 2011 at 5:00 PM

Why people are getting flat batteries;
I've seen this posted twice recently and people don't appear to be following the alarm manufacturer's instructions.
An external anti-grind/starter relay should be wired as follows:-
85 Only use the "ground when armed (GWA)" from the alarm.
86 Ignition 1 only.
87a Key side of starter
30 Starter side of cut wire and starter output from R/S.
Diode 1N4004 across 85 and 86 with the band towards 86.
If you join a constant 12V+ to 86 that relay will be on all the time and you will have a flat battery within a day.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.



Replies:

Posted By: syl20rochon
Date Posted: April 11, 2011 at 9:05 PM
Nice Howie, good tip.

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Sylvain Rochon
MECP security specialist
Tech support for remote starters
26 Years of experience counts
I'm here to help.




Posted By: sandoggg
Date Posted: May 05, 2011 at 9:37 AM

I installed a Compustar CM3000 on a manual 2001 Chrysler Sebring Coupe.  I am having the same problem.  For a while it was doing fine but if I don't use my car for a day it drains the battery flat.  I even bought a new battery thinking it wouldn't hold charge.

I followed the instruction for Conn#1 Pin 6 (yellow) hookup.  This is a pre-wired starter kill relay but I just remembered.  I removed the relay while installing the RS and plug it back when I was done.  Was there a possibility I plugged it in wrong?  Does the relay plug in only one way or could it be plugged in the wrong way?   

I also am looking at a Firstech Inst on the same alarm but their hookup instruction is different:

30-key side, 87a-starter side, 85-CN1 of RS, 86-red

Pls. help.  I'm just about to yank this "thing" out.  Thanks to all!  



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disco77




Posted By: howie ll
Date Posted: May 05, 2011 at 9:40 AM
No you can't plug it in the wrong way. 86 Red should be live on ignition and start.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: sandoggg
Date Posted: May 05, 2011 at 10:38 AM

Would you suggest  I remove the pre-wired harness and hook up using the outline you showed?  Maybe the pre wired harness is wired wrong?  One clarification...what happens if you hookup 87a and 30 the otherway around?  I see both ways on other sites.

By the way, if this is set up is hooked up wrong would the car start?  I also had a problem of intermittent starting.  The car would just turn over but never start...then sometimes it would.. 

Thanks

   



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disco77




Posted By: howie ll
Date Posted: May 05, 2011 at 12:44 PM
My previous post is the only right way to do this. Just make sure 86 is ignition and start live only. The intermittent start problem is nothing to do with this.Check your by-pass if fitted and the quality of your wiring connections. 87a and 30 can go the other way round but then it's easier to make 87 the starter output from the R/S.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: toran
Date Posted: August 01, 2011 at 10:19 PM
"If you join a constant 12V+ to 86 that relay will be on all the time and you will have a flat battery within a day."

Would this also explain a slow drain that kills the battery in a couple of days?
I notice that with alarm off, the following day the battery remains at about 12.1 to 12.2 volts.
With the alarm on, the following day the battery is between 11.7 to 11.9 volts.

T.I.A.





Posted By: scourage
Date Posted: August 15, 2011 at 10:54 PM

I'm new here, I came here with a different question I had about the starter cutout relay but came accross this thread.  I just purchased a Crime Guard Alarm/Remote Start system, so I decided to look at the included Starter cutout relay which includes the diode, but the band is towards 85, not 86.  Did they wire this incorrectly?





Posted By: howie ll
Date Posted: August 16, 2011 at 2:44 AM
It doesn't matter which way the coil is wired, the international convention states that 85 is the NEG and 86 the POS of the coil and the band faces the POS. If they've made 85 the POS (ignition), fine but that asks questions about the quality of the whole.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: oldspark
Date Posted: August 16, 2011 at 4:13 AM
Howie x2.

Be aware that +12V goes to the band-end terminal, ie, #85, NOT #86.

I know that is what Howie wrote, but just in case it isn't clear. (That's my Sir i am an idiot helpful clarification (aka: due-diligence) for the day.)

And does Howie x2 mean Howie IIII? Mind you, I thought he would have been promoted from Platinum by now.... (ie - Howie's "fire" warning from a few days ago).

PS - although I hate diode-protected relays - and by that I mean that I prefer to add my own EXTERNAL diode - I consider it UNFORGIVABLE that anyone market a diode-protected relay that breaches the Kathode = band = #86 convention. (Unless PERHAPS extremely highlighted with warnings, or a totally pre-wired item etc.)




Posted By: howie ll
Date Posted: August 16, 2011 at 5:37 AM
X 2 with Oldie, does that make me Howie 8? The point is
85 = Neg side of coil,
86 = POS side of coil
Above two are by international convention, in fact it doesn't matter or5 even better remove it from the relay and place in line on the alarm's GWA, neg when armed with the diode band towards the alarm.
30 input and 87 output.
Again in real life doesn't matter but with a 5 pin, 87a is connected at rest to 30; on activation 87a is connected to 30.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: oldspark
Date Posted: August 16, 2011 at 6:16 AM
ImAnIdiot Due Diligence #2 for 20110816:

As corrected:
howie ll wrote:

Again in real life doesn't matter but with a 5 pin, 87a is connected at rest to 30; on activation 87 is connected to 30.

IE - 87 to 30 is closed when activated, not 87a.

Otherwise correct, a relay coil doesn't care about the 85 & 86 polarity (+ or -), it is only when adding a spike-suppression diode that it is important. Get the diode wrong, and it will burn out (since it's a short from +12V to - or gnd) which may damage the controlling circuit (alarm) due to over-current etc, but shouldn't have detrimental effects on the relay; the diode can be replaced. So too any burnt skin or maybe any damaged eye injured during the diode burn-out. In case of fire etc, consult your insurance policy, but the supply of a relay-diode in contravention of the normal conventions should rule out any "Act of God" insurance clauses. (But check too for "Act of Idiots (other than yourself)" clauses.)




Posted By: howie ll
Date Posted: August 16, 2011 at 6:34 AM
Oops posted_image

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: tenchu
Date Posted: March 03, 2013 at 2:36 AM
howie ll wrote:

X 2 with Oldie, does that make me Howie 8? The point is
85 = Neg side of coil,
86 = POS side of coil
Above two are by international convention, in fact it doesn't matter or5 even better remove it from the relay and place in line on the alarm's GWA, neg when armed with the diode band towards the alarm.
30 input and 87 output.
Again in real life doesn't matter but with a 5 pin, 87a is connected at rest to 30; on activation 87a is connected to 30.


Thank you for this post... I will have to fix my relay in the morning. After reading your explanation, I would assume that this incorrect wiring would also prevent from the relay actually cutting off the starter?




Posted By: howie ll
Date Posted: March 03, 2013 at 3:16 AM
Yes.
Correct circuit. but if using a pre-supplied relay holder, always check if there's a diode present then look for the diode band. That's the POS side of the coil.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: tenchu
Date Posted: March 03, 2013 at 11:23 AM
There is a diode, should I replace with a regular relay?




Posted By: howie ll
Date Posted: March 03, 2013 at 11:26 AM
No, just make sure that the side your band points to is where your ignition + supply goes.
Frankly if you have to ask this question you shouldn't be attempting this install.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: oldspark
Date Posted: March 03, 2013 at 5:16 PM
Though in fairness, I reckon many competent wirers & DIYers can have problems with diodes.

But IMO, once the correlation between the diode symbol & its body-line are understood, then any application should be easy.
VIZ:
- (conventional) current flows from +ve to -ve,
- current only flows in the direction of the diode symbol's arrow;
- the arrow points into the perpendicular line which is at the same end as the line on the diode's body.

Also the ---|<-- symbol is like a "K", hence the line end is the Kathode = cathode, ergo the other and must be its anode. (That's in case readers strike those references.)


The only complication in this case (where used as a snubber or spike-protector across relay coils) is that the diode's -ve end (for normal current flow) goes to the +ve of the coil.
Though it may not be obvious that that is to short circuit the spike when the relay coil's -ve end (85) is more +ve than its 86 end, it should be obvious that if connected the other way (Kathode or line or "-ve" end to relay coil -ve & anode/+ve to 86), then that diode will conduct when 86 is +ve, and hence blow itself else the fuse or circuit driver since the diode conducts the current from 86 (+12V) to 85 (-ve or GND).

All the above is easy to see on a diagram with + & -/GND with a coil and the diode circuit symbol (with its arrow) and comparing the 2 diode connection possibilities.
(This should not be text only tutorial.)




Posted By: automatedsales
Date Posted: August 28, 2013 at 10:59 AM
informative post, I suddenly missed doing project

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Automated Sales




Posted By: overworked
Date Posted: September 07, 2013 at 5:57 PM
I often recommend to people using a pull up resistor instead of diode, this way they can wire the coil any direction they want.




Posted By: SKratch
Date Posted: November 08, 2013 at 9:09 PM
Wouldn't wiring the +(86) trigger to ignition alleviate all of this..?
I mean, that's the way I learned it.
Why would you need the relay active unless the ignition is turned on (in attempted theft) anyway?
That way the starter is only interrupted during the violation.
Diodes, polarity bias, etc wont matter as much in that case, right?

*shrug




Posted By: mikedelta
Date Posted: December 30, 2013 at 3:24 PM
This may be a stupid question, but does it matter which way you hook up 87a & 30?

According to the instruction manual for my Compustar CM5000 it is telling me that 87a goes to the starter side, and 30 goes to the key side.

Should I switch these wires to prevent battery drain?

86 is wired to the RS Ign, and 85 is to a GWA





Posted By: oldspark
Date Posted: December 30, 2013 at 10:51 PM
No.
Interchanging 30 & 87 or 30 & 87a never matter if only 2 contacts are used (ie, in plain "on-off" mode; NOT changeover mode that uses not all 3 of 30, 87 & 87a).

In fact when I use an SPDT changeover relay as a mere SPST, I will often connect the input (+12V) to 87 or 87a to avoid exposed unused "hot" terminals.




Posted By: mandofever
Date Posted: December 31, 2013 at 10:31 AM
Like Mikedelta, I am installing a CM5000 and there is no diode included on the prewired relay or harness. Should i add it to the GWA wire like Howie II mentioned earlier in this thread, band side towards RS unit?





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