12v switched pwr source
07-13-2012, 11:29 AM
#1
Mopar Fan
Thread Starter
12v switched pwr source
I'm putting on a new Edlebrock 4 bbl carb w/ electric choke on my 383 (slightly larger carb than last one). The choke has to be wired to a "switched" 12v pwr source...meaning the choke will only see current when the ign key is turned. I don't want to have to run wire for this thing all the way back to the fuse block (and thru the fire wall)...any place else under the hood where I could pick up switched 12v for the choke?
07-13-2012, 04:19 PM
#4
I think there was a thread on this awhile back, here is the problem:
There is ONLY ONE switched 12V power under the hood, and that is the (traditional dark blue) "ignition run", or "IGN1" wire. THIS WIRE IS NOT FUSED, and furthermore, has enough load on it, combined with deteriorating bulkhead connectors on these old girls, that adding more load might not be a good idea
One way you can work around this is to trigger a relay off the "switch" sided of the ballast resistor, and draw power for the relay contacts (fused) off the big stud on the start relay.
Another thing you should CHECK while you are doing this, is to see what condition the igntion harness is actually in, "voltage drop" wise
So...........turn the key to "run" with engine off, and hook a voltmeter from ground to the key side of the ballast resistor. You should measure VERY close to battery.
A better way of measuring this is to measure the harness drop directly. Hook your meter to the switch side of the ballast, and the other probe to battery POSITIVE. You should read a VERY low voltage, the lower the better. If you read higher than .2--.3V (three TENTHS of one volt) you need to find out where you are losing power
Your top suspects are, the bulkhead connector, the ignition switch connector, the switch itself, the ammeter, and the "welded splice" in the under--dash harness.
For a read on the how and why of the bulkhead connector problem, read this:
http://www.madelectrical.com/electri...p-gauges.shtml
If you scroll down the page to the simplified diagram, you can see the two feeds through the bulkhead. But there is ONE MORE not shown, and that is the ignition switch feed coming off the "welded splice", through the switch and it's connector, and BACK OUT the bulkhead connector on the "dark blue" ignition run buss.
Drop in this circuit WILL cause overcharging (overvoltage) when running, because the regulator "senses" off this same line.
There is ONLY ONE switched 12V power under the hood, and that is the (traditional dark blue) "ignition run", or "IGN1" wire. THIS WIRE IS NOT FUSED, and furthermore, has enough load on it, combined with deteriorating bulkhead connectors on these old girls, that adding more load might not be a good idea
One way you can work around this is to trigger a relay off the "switch" sided of the ballast resistor, and draw power for the relay contacts (fused) off the big stud on the start relay.
Another thing you should CHECK while you are doing this, is to see what condition the igntion harness is actually in, "voltage drop" wise
So...........turn the key to "run" with engine off, and hook a voltmeter from ground to the key side of the ballast resistor. You should measure VERY close to battery.
A better way of measuring this is to measure the harness drop directly. Hook your meter to the switch side of the ballast, and the other probe to battery POSITIVE. You should read a VERY low voltage, the lower the better. If you read higher than .2--.3V (three TENTHS of one volt) you need to find out where you are losing power
Your top suspects are, the bulkhead connector, the ignition switch connector, the switch itself, the ammeter, and the "welded splice" in the under--dash harness.
For a read on the how and why of the bulkhead connector problem, read this:
http://www.madelectrical.com/electri...p-gauges.shtml
If you scroll down the page to the simplified diagram, you can see the two feeds through the bulkhead. But there is ONE MORE not shown, and that is the ignition switch feed coming off the "welded splice", through the switch and it's connector, and BACK OUT the bulkhead connector on the "dark blue" ignition run buss.
Drop in this circuit WILL cause overcharging (overvoltage) when running, because the regulator "senses" off this same line.
07-15-2012, 05:14 AM
#5
Mopar Fan
Thread Starter
I think there was a thread on this awhile back, here is the problem:
There is ONLY ONE switched 12V power under the hood, and that is the (traditional dark blue) "ignition run", or "IGN1" wire. THIS WIRE IS NOT FUSED, and furthermore, has enough load on it, combined with deteriorating bulkhead connectors on these old girls, that adding more load might not be a good idea
One way you can work around this is to trigger a relay off the "switch" sided of the ballast resistor, and draw power for the relay contacts (fused) off the big stud on the start relay.
Another thing you should CHECK while you are doing this, is to see what condition the igntion harness is actually in, "voltage drop" wise
So...........turn the key to "run" with engine off, and hook a voltmeter from ground to the key side of the ballast resistor. You should measure VERY close to battery.
A better way of measuring this is to measure the harness drop directly. Hook your meter to the switch side of the ballast, and the other probe to battery POSITIVE. You should read a VERY low voltage, the lower the better. If you read higher than .2--.3V (three TENTHS of one volt) you need to find out where you are losing power
Your top suspects are, the bulkhead connector, the ignition switch connector, the switch itself, the ammeter, and the "welded splice" in the under--dash harness.
For a read on the how and why of the bulkhead connector problem, read this:
http://www.madelectrical.com/electri...p-gauges.shtml
If you scroll down the page to the simplified diagram, you can see the two feeds through the bulkhead. But there is ONE MORE not shown, and that is the ignition switch feed coming off the "welded splice", through the switch and it's connector, and BACK OUT the bulkhead connector on the "dark blue" ignition run buss.
Drop in this circuit WILL cause overcharging (overvoltage) when running, because the regulator "senses" off this same line.
There is ONLY ONE switched 12V power under the hood, and that is the (traditional dark blue) "ignition run", or "IGN1" wire. THIS WIRE IS NOT FUSED, and furthermore, has enough load on it, combined with deteriorating bulkhead connectors on these old girls, that adding more load might not be a good idea
One way you can work around this is to trigger a relay off the "switch" sided of the ballast resistor, and draw power for the relay contacts (fused) off the big stud on the start relay.
Another thing you should CHECK while you are doing this, is to see what condition the igntion harness is actually in, "voltage drop" wise
So...........turn the key to "run" with engine off, and hook a voltmeter from ground to the key side of the ballast resistor. You should measure VERY close to battery.
A better way of measuring this is to measure the harness drop directly. Hook your meter to the switch side of the ballast, and the other probe to battery POSITIVE. You should read a VERY low voltage, the lower the better. If you read higher than .2--.3V (three TENTHS of one volt) you need to find out where you are losing power
Your top suspects are, the bulkhead connector, the ignition switch connector, the switch itself, the ammeter, and the "welded splice" in the under--dash harness.
For a read on the how and why of the bulkhead connector problem, read this:
http://www.madelectrical.com/electri...p-gauges.shtml
If you scroll down the page to the simplified diagram, you can see the two feeds through the bulkhead. But there is ONE MORE not shown, and that is the ignition switch feed coming off the "welded splice", through the switch and it's connector, and BACK OUT the bulkhead connector on the "dark blue" ignition run buss.
Drop in this circuit WILL cause overcharging (overvoltage) when running, because the regulator "senses" off this same line.
--- 440roadrunner, thanks for the info, I've heard from some other guys doing the same thing to get pwr for the measly choke. I've never had any "electrical" gremlins with the car---so far, much unlike alot of other folks I've been reading about here, guess I should check it out and maybe avoid unneeded heartaches.
Thread
Thread Starter
Forum
Replies
Last Post
78pwrwagon440
Transmissions, Transfer Cases and Rear Ends
1
08-02-2012 12:26 PM
