High beam causing a buck
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,277
Likes: 9,417
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
So the original cloth wire according to the wiring diagram for TI would have come from the pulse amplifier and shows a resistor. How has this wire been modified to eliminate the resistor and the pulse amplifier? Diagram in link below.
TI Diagram.
TI Diagram.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Anther poster has some good suggestions that I’m going to try.
I appreciate it.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Yes the spade is tied into the ignition switch but may be clean power. BUT
Now that I know you are tied into the old cloth covered wire those had a voltage drop when the car was started...Dont know how the light switch being an issue there but it is explicitly stated not to use those wires on an HEI distributor. The back of the ignition switch has a lot of different sources so that is why I was saying that it could be coming through the light switch. The IGN post should be a clean source from the battery or the horn relay. I havent traced it. I take it you are running your MSD under the hood in the engine compartment so try this...
This may be a solution for you. Use the Ignition wire you are currently using trigger a relay and take a direct power line off the horn relay buss bar as power for the MSD trigger through that relay. Y0u already know that is not an issue and the ignition wire voltage at the trigger side of the relay may be sufficient to keep the relay closed while you are running.
this will keep you from having to run a wire through the firewall
Now that I know you are tied into the old cloth covered wire those had a voltage drop when the car was started...Dont know how the light switch being an issue there but it is explicitly stated not to use those wires on an HEI distributor. The back of the ignition switch has a lot of different sources so that is why I was saying that it could be coming through the light switch. The IGN post should be a clean source from the battery or the horn relay. I havent traced it. I take it you are running your MSD under the hood in the engine compartment so try this...
This may be a solution for you. Use the Ignition wire you are currently using trigger a relay and take a direct power line off the horn relay buss bar as power for the MSD trigger through that relay. Y0u already know that is not an issue and the ignition wire voltage at the trigger side of the relay may be sufficient to keep the relay closed while you are running.
this will keep you from having to run a wire through the firewall
I appreciate it!
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,277
Likes: 9,417
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 certainly hope it gets you back on the road before it snows!!!
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,277
Likes: 9,417
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 certainly hope it gets you back on the road soon...we are getting close to salting time which shuts down driving up here!!
Pro
Joined: Nov 2023
Posts: 707
Likes: 335
From: Aubrey TX
I requested a copy of the 69 wiring diagram to take a look. Meanwhile I have a 71 diagram and I suspect the ignition switch and headlight switch portion is not much different from the 71 if not identical. So Im using that diagram until I get the 69 diagram to verify but I suspect your problem is an interruption in the wire that comes from the ignition switch. The power TO the headlight switch and the ignition switch comes from the same source. If the high beam switch is malfunctioning where for that brief moment when you select high beams on then off then it would affect the same power to the ignition switch. I think your problem is not the main power to the MSD box, I think its the ign wire to the MSD that is getting interrupted for a brief moment.
To test this, (temporarily) disconnect the +12V ignition line to the MSD and run a jumper wire to the red wire that powers the MSD from the starter. Fire up the car and test the high beams and see if you get the stumble or if it goes away. At that point you will know for sure if that is what is interrupting your ignition.
I suspect the high beam switch is failing.
To test this, (temporarily) disconnect the +12V ignition line to the MSD and run a jumper wire to the red wire that powers the MSD from the starter. Fire up the car and test the high beams and see if you get the stumble or if it goes away. At that point you will know for sure if that is what is interrupting your ignition.
I suspect the high beam switch is failing.
Burning Brakes
Joined: Nov 2013
Posts: 890
Likes: 473
From: Central NJ
Glad you found it. Bad ground problem is hard cause it looks like it's attached, but ......
I was pulling my hair out with a loose connection problem for over a year, Finally found it when running the power window caused my headlamp buckets to go down.
I was pulling my hair out with a loose connection problem for over a year, Finally found it when running the power window caused my headlamp buckets to go down.
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Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
I forgot that I was not using the original 12v source for that trigger wire.
During the same project, I got a new carb…. New carb has electric choke. I used that 12v source for the electric choke. When I hooked the MSD back up…. I used an unused wire on the ignition circuit…. The cloth covered wire. When I tested the wire to see if it had voltage (12v) only when the ignition switch was on… it did.
Unbeknown to me, that cloth covered wire is a resistor wire part of the old Transistor Ignition. As such, yes this being a resistor wire has inconsistent voltage…. Drops under 12v momentarily when turning headlights on, and also other components…
🤦
Solution…. Move the wire I used for the electric choke back to being the MSD trigger wire. Use the cloth wire for the electric choke…. Since the choke isn’t sensitive to momentary voltage changes.
All running perfect.
sorry I didn’t update sooner
Drifting
Joined: Oct 2024
Posts: 1,656
Likes: 383
From: Toronto, Ontario
OK, you're gathering information.
PLEASE, go to Mad Electrical's Web site.
Please!
I simply cannot take the time to type this much when they already have!
Please, top of their home page, tech pages. Read all about charging systems, read about headlight relays, and how and why to wire them.
I am done here. I tried.
PLEASE, go to Mad Electrical's Web site.
Please!
I simply cannot take the time to type this much when they already have!
Please, top of their home page, tech pages. Read all about charging systems, read about headlight relays, and how and why to wire them.
I am done here. I tried.
