C3 - Headlight Switch Draining Batt??
Thread Starter
Instructor
Joined: Aug 2021
Posts: 216
Likes: 46
From: Los Angeles
C3 - Headlight Switch Draining Batt??
Hey Folks,
1971 C3 with stock headlight switch.
When I connect the switch, the battery seems to drain.
The batt does not drain when the headlight switch is not connected.
Where/How do I test to find the source?
None of the interior lights are left on.
Doesn't matter if the key is in/out.
Thanks
1971 C3 with stock headlight switch.
When I connect the switch, the battery seems to drain.
The batt does not drain when the headlight switch is not connected.
Where/How do I test to find the source?
None of the interior lights are left on.
Doesn't matter if the key is in/out.
Thanks
Thread Starter
Instructor
Joined: Aug 2021
Posts: 216
Likes: 46
From: Los Angeles
Battery is draining. 1 day and it's dead.
I spoke with someone this morning who thinks it might be the horn relay. I haven't finished the interior, including the horn install, so something could be going on there.
I do need to look for the drain, however. Not sure HOW to do that.
I spoke with someone this morning who thinks it might be the horn relay. I haven't finished the interior, including the horn install, so something could be going on there.
I do need to look for the drain, however. Not sure HOW to do that.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,153
Likes: 9,283
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
I helped a member years ago and his was a light bulb that was drawing enough current to drain the battery but not enough to light the bulb...THis is how I would do it with just a multimeter..
- disconnect the positive cable to the battery
- attach an OHM meter between the positive lug on the battery and the cable so the power has to flow through the meter
- set the meter to amps on its lowest setting for a reading that would be x.xx so you can see a tiny draw
- with the headlight switch disconnected you should see zeros if you do not have a clock or a radio with a memory. they will show a small draw. you can pull the fuse for these or just use that number as the baseline.
- if you do have a substantial draw of .2 or more amps that will probably kill the battery over night. Disconnect the wiper relay wires and see if it goes away. IF you do not have a draw then go to the next step
- plug in the headlight switch and see what the draw is. If it has increased then you do have a problem.
- start disconnecting light bulbs one at a time and with each bulb, see if the draw has decreased....hopefully you wont have to pull the dash. Start with all the easy bulbs like the headlights, courtesy lights, then marker and tail lights. Remember, they dont have to be lit to be causing an issue
Race Director
Joined: Mar 2017
Posts: 11,923
Likes: 4,495
From: Virginia
I only have ATC/ATO fuses in my cars (which started in 79 in C3s), so I couldn't find a quick solution for testing individual circuits with glass fuses.
But for ATC fuses, I bought one of these Fuse Buddy kits (with the add-ons to do other size blade fuses found in newer cars).
if you pull a fuse, or use a popped fuse, you might be able to bridge the circuit with the ATC spade spacing, or you could use one of these (surprisingly expensive) glass fuse to ATC converters (which looks to be a non-conductive ceramic tube, with two slots to hold the ATC fuse, which will work directly with the Fuse Buddy, or similar).
https://www.npdlink.com/product/glas...ion-kit/220224
If you pull all the fuses, and still can't find the drain, it is likely to be from your alternator, either from a leaky diode, or from the alternator being excited when the car is off. @Rescue Rogers instructions will show that pretty clearly.
But for ATC fuses, I bought one of these Fuse Buddy kits (with the add-ons to do other size blade fuses found in newer cars).
if you pull a fuse, or use a popped fuse, you might be able to bridge the circuit with the ATC spade spacing, or you could use one of these (surprisingly expensive) glass fuse to ATC converters (which looks to be a non-conductive ceramic tube, with two slots to hold the ATC fuse, which will work directly with the Fuse Buddy, or similar).
https://www.npdlink.com/product/glas...ion-kit/220224
If you pull all the fuses, and still can't find the drain, it is likely to be from your alternator, either from a leaky diode, or from the alternator being excited when the car is off. @Rescue Rogers instructions will show that pretty clearly.
Melting Slicks
Joined: May 2021
Posts: 2,263
Likes: 1,308
From: Fleming Island, FL
When checking amperage with a VOM, you should start with the highest setting first and work your way down. To much current going through a VOM at the lower setting can damage a VOM.
