Installing ignition relay

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hotrod swinger

hotrod swinger

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I have a voltage drop in my ignition circuit of 1.14 volts, which means I am running high voltage of just over 15 volts.

I’d like to install an ignition relay in the engine bay to take the load off my ignition switch, connector and bulkhead connector and eliminate this problem so I can save my switch, connectors, etc.

Any practical tips or ideas about this installation?

73 Dart
Stock wiring, except:
Bulkhead bypass
Cracked back headlight harness
Ammeter bypass

Thanks!
 
67dart273 posted this info in another thread I was highjacking:
CD296D88-95B5-4DBD-A0BE-ECF6AD6C29AB.png
 
hotrod swinger said:
I have a voltage drop in my ignition circuit of 1.14 volts, which means I am running high voltage of just over 15 volts.

I’d like to install an ignition relay in the engine bay to take the load off my ignition switch, connector and bulkhead connector and eliminate this problem so I can save my switch, connectors, etc.

Any practical tips or ideas about this installation?

73 Dart
Stock wiring, except:
Bulkhead bypass
Cracked back headlight harness
Ammeter bypass

Thanks!
Click to expand...
You have issues that need addressed if your voltage is that high. It should be about 14.2.
 
^^Somebody already posted "my stuff" LOL^^ And that is certainly one way around it. The thing is at least part of the drop can be right in the ignition switch contacts, and a "new" switch may not fix that Feed the power to the relay from say, the starter relay "big stud" and use a 20 or 30A fuse inline or breaker. Keep either away from engine heat as much as you can
 
hotrod swinger said:
Yes, and I have clearly identified my issue in the first post lol
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My point was fix your voltage drop issue and you won't need a relay for your ignition switch. You need to fix the source of your overcharging issue. Your list of bandaids and bypasses may not fix the issue. It could be as simple as a poorly grounded voltage regulator.
 
It’s not a poorly grounded voltage regulator. I have been meticulous in my ground connections. I know what the problem is, and I’ve stated in my initial post.

Lol, I ask again, any practical tips or pointers to install the ignition relay?
 
I was thinking I would disconnect my ignition wire from the bulkhead connector, attach that to 87 on the relay, and then run a new blue wire from 86 on the relay to the bulkhead connector, then attach the power and ground. If I do it this way my relay will be next to the bulkhead connector.
 
toolmanmike said:
My point was fix your voltage drop issue and you won't need a relay for your ignition switch. You need to fix the source of your overcharging issue. Your list of bandaids and bypasses may not fix the issue. It could be as simple as a poorly grounded voltage regulator.
Click to expand...
The ignition harness IS the drop issue and as I said the switch is part of the problem. You can install 20 new china switches in there and the problem may or may not be fixed. Relays are not band aids. Relays are what all modern vehicles use in large amounts in order to solve voltage drop issues. My three pickups use something like 10 relays apiece
 
hotrod swinger said:
I was thinking I would disconnect my ignition wire from the bulkhead connector, attach that to 87 on the relay, and then run a new blue wire from 86 on the relay to the bulkhead connector, then attach the power and ground. If I do it this way my relay will be next to the bulkhead connector.
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You can do exactly that. Take care to mount the relay to reduce weather problems or try to find a weatherproof relay, in any case mount it "pins down, case up"
 
67Dart273 said:
The ignition harness IS the drop issue and as I said the switch is part of the problem. You can install 20 new china switches in there and the problem may or may not be fixed. Relays are not band aids. Relays are what all modern vehicles use in large amounts in order to solve voltage drop issues. My three pickups use something like 10 relays apiece
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Oh I agree with you there. Relay's are a great design. My point was installing a relay instead of repairing the voltage drop is a band aid.
 
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Just getting ready to do my ignition relay. Can I have recommendations for wire gauge sizes?

Thanks!
 
If you don't have anything extra in the engine bay such as pumps, electric fans, in other words you are supplying a common ignition system and the VR, then what is there is larger enough, no 14 would be "overkill" for a stock type ignition.

The big issue here is the terminals in the bulkhead connector, the ignition switch connector, and often the switch itself. that whole path "adds up," a tenth here, 4 tenths there, etc.
 
You listed a bulkhead bypass? What is this? Just curious.
Also you listed the Ammeter bypass. I'm not sure how you made the connections for that but sometimes just a poor soldering job can cause the issues you describe.
How are you measuring the voltage drop for the ignition circuit?
Engine bay wiring takes a beating from heat, etc. So a worn out wire is still going to be a worn out wire regardless if you install a relay or not.

You came here ands asked for help and this is my $0.02.
 
If you have the voltage drops (resistance) fixed, really don't see the need.
 
Mattax said:
If you have the voltage drops (resistance) fixed, really don't see the need.
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Thanks Matt, I was wondering about that too. I’m going to check my voltage drop again because when I repaired my under dash harness this weekend I discovered the ignition wire insulation was melted in one section and I repaired that. Maybe that was the last area causing resistance.
 
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if you have a laser thermometer, you could find that voltage drop as that will create heat (conservation of energy) along the harness. energize your circuit and let it sit a minute and start lasing your harness an inch at a time. Maybe a big temperature spike will be evident and a warm (high resistance) joint will be found.
 
If you buy a relay for your ignition, don't by a 5 pin, get a 4 pin with only an 87 terminal. The 87a terminal is useless for your application.

Based soley on the relay picture above.

14ga wire should be fine if all you are doing is what you mentioned earlier about moving the bulkhead wires and new run to trigger relay.
 
hotrod swinger said:
It’s not a poorly grounded voltage regulator. I have been meticulous in my ground connections. I know what the problem is, and I’ve stated in my initial post.

Lol, I ask again, any practical tips or pointers to install the ignition relay?
Click to expand...

You stated that the problem is overcharging but you didn't state why it's overcharging. People are trying to help you with the overcharging problem but it sounds like you don't want to fix the actual overcharging problem, you just want to let it overcharge and work around it melting your components by using relays?

Forgive me if my reading comprehension is way off but I don't understand this or your replies to the first few posts at all.
 
66 Valiant wagon said:
So a worn out wire is still going to be a worn out wire regardless if you install a relay or not.
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That may be true, but there won’t be any significant current travelling through that wire.

ESP47 said:
You stated that the problem is overcharging but you didn't state why it's overcharging.
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Yes, I stated clearly it is a voltage drop in the ignition circuit.

ESP47 said:
People are trying to help you with the overcharging problem but it sounds like you don't want to fix the actual overcharging problem, you just want to let it overcharge and work around it melting your components by using relays?
Click to expand...

Adding a relay to the ignition circuit will fix the problem, and that was the initial question posed in the thread.

ESP47 said:
Forgive me if my reading comprehension is way off but I don't understand this or your replies to the first few posts at all.
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Not sure how I can help with that, hire a tutor maybe?
 
hotrod swinger said:
That may be true, but there won’t be any significant current travelling through that wire.



Yes, I stated clearly it is a voltage drop in the ignition circuit.



Adding a relay to the ignition circuit will fix the problem, and that was the initial question posed in the thread.



Not sure how I can help with that, hire a tutor maybe?
Click to expand...

Voltage drops on the ground side cause over charging and voltage drops of the positive side cause undercharging. You're overcharging so you should be looking at your ground circuits. But it sounds like you have it all figured out. So much so that you have to ask for help on here and then be rude to the people who try to help you out. Good luck.
 
ESP47 said:
Voltage drops on the ground side cause over charging and voltage drops of the positive side cause undercharging. You're overcharging so you should be looking at your ground circuits. .
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No, that is not true. Voltage drop is "drop." They both cause OVER charging because the VR sees UNDER voltage and "it thinks" it needs to ramp up output to obtain 14V nominal AT THE VR terminals
 
Checked my ignition circuit after repairing my under dash harness, still have a 0.6V drop.

What I’m hearing is a 14 gauge wire to power the relay. Should I draw power from the battery or the alternator?
 
Starter relay big stud. What you are trying to do is to lock the VR "ign" terminal to the battery voltage
 
Another thing I’m wondering about is protecting the remaining charging circuit.

After I install my ignition relay, I will have done the following modifications:

1. Jump wire from alternator to battery with fusible link
2. Remove ammeter and replace with voltmeter
3. Headlight relay
4. Ignition relay

How do I protect the factory charging circuit? Obviously the fusible link didn’t protect it, because the wires were all melted together at some point. With my jumper wire I understand that the current to the cabin is now divided equally between the red and black wires entering the cabin, the former charging circuit.

How do I protect those wires? Should I add inline fuses between the battery and the bulkhead connector, as well as between the alternator and bulkhead connector? If so, what amperage?
 
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