[C2] I need electrical help
#1
Team Owner
Thread Starter
I need electrical help
I need some help. I chased down a small current drain on my 65 and it turned out to be the aftermarket radio I had installed. No big deal, I just changed the wire for memory over to the switched radio connector so that it only holds memory when the key is on. I never listen to the radio anyway, so I"m ok with that.
Here's where I need help. While checking current draw with the negative battery lead disconnected and an ammeter in series with the negative post and the disconnected negative cable, what current should I read if I turn ignition to ON? I've never checked that before, and mine reads 4.6 amps. That seems high to me. It only reads 6.5 amps when the backup lights are on in addition. With the key in off position, I'm getting .001 amps, and in acc I'm getting about 1 amp. I know the key supplies voltage to the coil, and to the alternator, but everything else is off. Has anyone ever done that test before, checking draw with key ON?
When I turn the key to ON the battery gauge on the dash moves to the negative very slightly, but not much and I would expect that. Where are the 4 amps going?
Just FYI, I also have Classic Auto Air, Detroit Speed head light conversion, and 4 way flasher added. The headlight conversion works with the key off, so I don't think that's an issue since it's not drawing at all with the key off. I checked the courtesy lights and the glove box light and all are off. Any ideas? Maybe it's normal?
Here's where I need help. While checking current draw with the negative battery lead disconnected and an ammeter in series with the negative post and the disconnected negative cable, what current should I read if I turn ignition to ON? I've never checked that before, and mine reads 4.6 amps. That seems high to me. It only reads 6.5 amps when the backup lights are on in addition. With the key in off position, I'm getting .001 amps, and in acc I'm getting about 1 amp. I know the key supplies voltage to the coil, and to the alternator, but everything else is off. Has anyone ever done that test before, checking draw with key ON?
When I turn the key to ON the battery gauge on the dash moves to the negative very slightly, but not much and I would expect that. Where are the 4 amps going?
Just FYI, I also have Classic Auto Air, Detroit Speed head light conversion, and 4 way flasher added. The headlight conversion works with the key off, so I don't think that's an issue since it's not drawing at all with the key off. I checked the courtesy lights and the glove box light and all are off. Any ideas? Maybe it's normal?
#2
Drifting
Current Draw
Hi 65GGVERT,
Assuming your battery is roughly at 12 volts, the primary resistance of your coil is .5 ohms, the ballast resistor is about 2 ohms, and the resistance across the points is .1 ohm, 4.6 amps is right on the nose.. 12 volts divided by 2.6 ohms equals about 4.6 amps.
RON
Assuming your battery is roughly at 12 volts, the primary resistance of your coil is .5 ohms, the ballast resistor is about 2 ohms, and the resistance across the points is .1 ohm, 4.6 amps is right on the nose.. 12 volts divided by 2.6 ohms equals about 4.6 amps.
RON
Last edited by rongold; 07-16-2018 at 05:24 PM.
#3
Team Owner
Thread Starter
I guess I should have bumped it to see if the points were closed, thought about it but didn't want to blow my 10a meter. I'll check it to see if they're closed. Thanks.
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Hi 65GGVERT,
Assuming your battery is roughly at 12 volts, the primary resistance of your coil is .5 ohms, the ballast resistor is about 2 ohms, and the resistance across the points is .1 ohm, 4.6 amps is right on the nose.. 12 volts divided by 2.6 ohms equals about 4.6 amps.
RON
Assuming your battery is roughly at 12 volts, the primary resistance of your coil is .5 ohms, the ballast resistor is about 2 ohms, and the resistance across the points is .1 ohm, 4.6 amps is right on the nose.. 12 volts divided by 2.6 ohms equals about 4.6 amps.
RON
Dan
#5
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Depending on the amp rating of the alternator you field draw could be from 2-5A. Disconnect the two wire plug at the back of the alternator and see if the amps drop off.
Joe
Joe
#7
Team Owner
Thread Starter
I disconnected the red wire, no change, didn't try the plug. I'll do that next time out. The battery gauge in the dash just barely twitches when I turn the ignition on, just like they usually do. Reads positive when I start it.. I just never measured current with the battery disconnected and switch on before.
#8
Team Owner
Thread Starter
Disconnected the plug from the alternator and the current dropped very slightly to 3.9 amp. I have a friend with the same car, I'll measure his next time I'm over.
#9
Advanced
I work on these cars and I think you are chasing a ghost. A few amps at key on is fine. Gauges and senders have to be powered. Alternator, regulator, etc. When you said in your post that you turned the key on I was expecting the fuse in the meter to pop. It more than likely would on a modern car many of which don't use a battery that is much bigger than what is correct for your 65. I wouldn't worry about it, its in the range of normal.
#10
Team Owner
I thought it was prob OK too. But when 65GGvert asks for electrical help I got scared and didn’t respond I expect a meteor to strike the earth any day now.
#11
Le Mans Master
LOL!!! I was thinking the same thing. 65GGvert is the "go to" guy for electrical issues. Let us all know if it turns out to be an "issue" or is completely normal.
#12
Team Owner
Thread Starter
Thank you to those who responded, I appreciate it. I'll still measure the friend's 65 sometime this week since it's sitting with the battery cutoff open and all I need to do is clip on the ammeter, but I think you're right about it being normal.
#13
Team Owner
Thread Starter
I work on these cars and I think you are chasing a ghost. A few amps at key on is fine. Gauges and senders have to be powered. Alternator, regulator, etc. When you said in your post that you turned the key on I was expecting the fuse in the meter to pop. It more than likely would on a modern car many of which don't use a battery that is much bigger than what is correct for your 65. I wouldn't worry about it, its in the range of normal.
Last edited by 65GGvert; 07-17-2018 at 12:43 PM.
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[QUOTE=65GGvert;1597613871 The b/u lamps only drew 2 additional amps, so it made me curious what would draw 4 amps...….but I think you're right about it being normal.[/QUOTE]
The alternator field coil came to mind as it goes hot with key on (as does the field relay coil in the regulator). 4 amps isn't much given 12 volts (but you knew that). I might have been just as curious as you!
Dan
The alternator field coil came to mind as it goes hot with key on (as does the field relay coil in the regulator). 4 amps isn't much given 12 volts (but you knew that). I might have been just as curious as you!
Dan
#15
Drifting
You know this is funny, I have not been here for a very long time, but it would be hard to deny that 65GGvert has his s--t together when it comes to electrical issues. it reminds me of the time someone checking AC voltage decided to switch the fluke meter to DC and measured 12 volts DC on an AC system, when asked why he did it he said he wanted to see what it would measure if anything at all. but that's a very long story. it turned out that there was 12 volts DC running along the neutrals on an AC system.
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You know this is funny, I have not been here for a very long time, but it would be hard to deny that 65GGvert has his s--t together when it comes to electrical issues. it reminds me of the time someone checking AC voltage decided to switch the fluke meter to DC and measured 12 volts DC on an AC system, when asked why he did it he said he wanted to see what it would measure if anything at all. but that's a very long story. it turned out that there was 12 volts DC running along the neutrals on an AC system.
Dan
#17
#18
Advanced
I was curious so I looked at the key on draw of 70 which is the closest I could get with whats in the shop right now. Very similar electrically except the 70 has some minor differences. And, the 70 had 7.5 amps draw at key on with everything off. It just got me curious as well so I thought I'd share what I got off of a similar car with no known electrical issues.
**Wanted to correct this. 80 is the first year of the computer. We have one in the shop with issues related to the computer and just got my wires crossed early morning."**
**Wanted to correct this. 80 is the first year of the computer. We have one in the shop with issues related to the computer and just got my wires crossed early morning."**
Last edited by Russell Boulding; 07-18-2018 at 10:22 AM. Reason: Misspoke about a year. Didn't want confusing info out there.
#19
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I was curious so I looked at the key on draw of 70 which is the closest I could get with whats in the shop right now. Very similar electrically except the 70 has some early computer controls and minor differences. And, the 70 had 7.5 amps draw at key on with everything off. The computer accounts for some of that of course. It just got me curious as well so I thought I'd share what I got off of a similar car with no known electrical issues.
#20
Advanced
No you're absolutely right. We've got an 80 in the shop also and got my wires crossed for a second. Didn't even cross my mind until I read your comment. Coffee needs to kick in. 80 is the first year of the computer.