horn relay drains battery
November 21st, 2012, 08:08 AM
#1
TalksToToads
Thread Starter
Join Date: Oct 2010
Location: York, Pa.
Posts: 118
horn relay drains battery
Hi, the horn relay in my 68 Delta 88 is draining the battery, As soon as I disconnect the wire that goes to the battery it stops draining, but then the car won't start. I looked at the manual and it is hooked up correctly so I replaced it, but it is still draining. My plan is to run the wire to a switched source so it only has power when the key is on, but I'm afraid it is fairly high amp draw and will just blow whatever fuse I hook it to. Is there an easy way to hook it to the ignition switch without going to the fusebox? Like maybe something under the hood? Otherwise how can I find out what is causing it to drain? Thanks.
November 21st, 2012, 08:15 AM
#2
Registered User
Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
So does the horn itself work right?
If so, then the horn relay is not the problem.
That big stud just serves as a junction block to distribute power. Next step would be to put a current meter inline with the battery - and the - cable and see what you read. Key stays OFF during this test. Then start pulling fuses one by one until the current draw goes away. You might disconnect the regulator and alternator before the fuses to see if the issue is there.
If so, then the horn relay is not the problem.
That big stud just serves as a junction block to distribute power. Next step would be to put a current meter inline with the battery - and the - cable and see what you read. Key stays OFF during this test. Then start pulling fuses one by one until the current draw goes away. You might disconnect the regulator and alternator before the fuses to see if the issue is there.
November 21st, 2012, 08:33 AM
#3
TalksToToads
Thread Starter
Join Date: Oct 2010
Location: York, Pa.
Posts: 118
So does the horn itself work right?
If so, then the horn relay is not the problem.
That big stud just serves as a junction block to distribute power. Next step would be to put a current meter inline with the battery - and the - cable and see what you read. Key stays OFF during this test. Then start pulling fuses one by one until the current draw goes away. You might disconnect the regulator and alternator before the fuses to see if the issue is there.
If so, then the horn relay is not the problem.
That big stud just serves as a junction block to distribute power. Next step would be to put a current meter inline with the battery - and the - cable and see what you read. Key stays OFF during this test. Then start pulling fuses one by one until the current draw goes away. You might disconnect the regulator and alternator before the fuses to see if the issue is there.
November 21st, 2012, 10:49 AM
#4
TalksToToads
Thread Starter
Join Date: Oct 2010
Location: York, Pa.
Posts: 118
I pulled all of the fuses and none of them stopped it. When I unplug the little plug in the back of the alternator, the drain stops.
Last edited by CrazedCountryRebel; November 21st, 2012 at 11:37 AM.
November 21st, 2012, 07:55 PM
#9
Registered User
Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
The alt does not have a ground wire - it grounds through the case.
It is possible one of the diodes inside the alt have turned leaky. They can replaced after the alt is opened up. With key off, and plug plugged in, measure from the white wire to ground with a volt meter. If you get something, the diodes leak.
It is possible one of the diodes inside the alt have turned leaky. They can replaced after the alt is opened up. With key off, and plug plugged in, measure from the white wire to ground with a volt meter. If you get something, the diodes leak.
November 21st, 2012, 07:56 PM
#10
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
The horn relay does not have a ground wire. It grounds to the body.
In a '68, if I recall, there is no ignition key buzzer, so the relay has four terminals.
One is the ground.
One is the hot post to the battery.
One is the wire from the relay to the horn button, which is grounded when you blow the horn.
One is the wire to the horns.
That's it.
Press horn button —> ground horn button wire —> current flows from battery post through relay coil to ground, pulling contacts in and connecting battery post to wire to horns —> horns blow.
That's all there is.
No rocket science or magic.
- Eric
In a '68, if I recall, there is no ignition key buzzer, so the relay has four terminals.
One is the ground.
One is the hot post to the battery.
One is the wire from the relay to the horn button, which is grounded when you blow the horn.
One is the wire to the horns.
That's it.
Press horn button —> ground horn button wire —> current flows from battery post through relay coil to ground, pulling contacts in and connecting battery post to wire to horns —> horns blow.
That's all there is.
No rocket science or magic.
- Eric
November 21st, 2012, 08:07 PM
#11
Registered User
Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
He found the issue was with the alt.
November 21st, 2012, 08:25 PM
#12
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
Okay, I've got it now.
He replaced his horn relay because disconnecting the alternator (the wire to the battery) from the horn relay stopped the battery from draining.
Kind of like replacing the fuel pump because you've got a bad float needle.
Why do people replace parts first and troubleshoot later?
I think I'm in a bad mood.
- Eric
He replaced his horn relay because disconnecting the alternator (the wire to the battery) from the horn relay stopped the battery from draining.
Kind of like replacing the fuel pump because you've got a bad float needle.
Why do people replace parts first and troubleshoot later?
I think I'm in a bad mood.
- Eric
November 28th, 2012, 07:39 AM
#14
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,301
Okay, I've got it now.
He replaced his horn relay because disconnecting the alternator (the wire to the battery) from the horn relay stopped the battery from draining.
Kind of like replacing the fuel pump because you've got a bad float needle.
Why do people replace parts first and troubleshoot later?
I think I'm in a bad mood.
- Eric
He replaced his horn relay because disconnecting the alternator (the wire to the battery) from the horn relay stopped the battery from draining.
Kind of like replacing the fuel pump because you've got a bad float needle.
Why do people replace parts first and troubleshoot later?
I think I'm in a bad mood.
- Eric
November 28th, 2012, 08:40 AM
#15
Registered User
Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
On the horn relay in 72 -
One to the ALT, one to the regulator, one to the starter solenoid (where the + batt cable connects), one to the fuse box inside, one to the AC blower relay and one to the rear defroster (if you have it).
Two's of them's a crowd......
December 14th, 2012, 08:20 AM
#18
TalksToToads
Thread Starter
Join Date: Oct 2010
Location: York, Pa.
Posts: 118
The alt does not have a ground wire - it grounds through the case.
It is possible one of the diodes inside the alt have turned leaky. They can replaced after the alt is opened up. With key off, and plug plugged in, measure from the white wire to ground with a volt meter. If you get something, the diodes leak.
It is possible one of the diodes inside the alt have turned leaky. They can replaced after the alt is opened up. With key off, and plug plugged in, measure from the white wire to ground with a volt meter. If you get something, the diodes leak.
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