Hey everyone,

I'm trying to figure out a problem that's driving me nuts. I installed a modern radio in my '69 and followed this guide exactly:

https://www.corvetteforum.com/forums/c3-general/3031593-installation-guide-installing-an-aftermarket-radio-in-a-c3.html

Per this guide, I have a direct line from the battery positive terminal to the radio with an inline fuse.

When I turn the key to the "on" position everything works great. When I start the car, however, often the radio doesn't turn on (maybe 50% of the time). If I turn the car off and turn the key back to "on" without starting the engine, it usually works again. I have confirmed that the switched power is always getting power (I put a light in this circuit just to test). For some reason the wire that is a direct line from the battery stops getting power. I know, this doesn't make sense but here we are. It's not a fuse, ground is fine. I was just playing around with it while the engine was off but the switch was on. I could recreate it by disconnecting the direct line from the battery to the radio, reconnecting it, then disconnecting a couple times. Suddenly, the battery stops sending power but the other electronics in the car still work! If I disconnect the negative, reconnect the negative and try again, the radio starts working again.

Maybe related to this. Sometimes if I go to start the car soon after shutting it off the starter doesn't do anything, not even a click. Doesn't matter if the engine has been running 2 min or 2 hours; it's very intermittent. All the other electronics work. I disconnect the negative terminal, reconnect it, it starts right up. Clearly that resets something. Any help greatly appreciated.

 

Who's radio?

Here's a simple test- take the red- ignition switched wire and run it to the battery as well.
Start the car- if the radio works then it doesn't like the dirty power it is seeing from the ignition wire.
If it still doesn't work- bad radio ( China)- bad filtering- no shielding -bad design
If that works a simple relay would solve your problem- see below

 

How are you connecting to the side post battery? That would be my one of my first checks. I really dislike side posts….and be tricky and need to be tight to have a constant connection.

might explain your intermittent starting problem as well.

Don

 

All battery connections need to be properly tightened. Regardless of type. Absolutely nothing wrong with side post battery's.

 

Check the battery ground to the frame. If you are getting an occasional Dead start it could be the ground is a out to leave you stranded. Check the wire too. If its starting to bulge it could be internal corrosion which looks green. The other could be a loose connection at the starter, the main lug there is also a post for the rest of the cars power. Could be a bad connection there as well.

There are lots of possibilities when you throw in an occasional Bad start as a possible symptom. When the car is running there is a lot more power consumption going elsewhere and a bad connection makes that limited power worse

 

Thanks to everyone for your input. I'll start working down this list. As I've thought about more, I'm increasingly convinced something is going on with the radio itself. I can't figure out what it is but I'm going to play around with it a little more. After a bunch of google searches I found out there is a reset button behind the face. I'm going to mess with that tonight to see if I can get something to happen.

My question on the starter issue is the "reset" that happens when the battery negative terminal is disconnected and then reconnected. What would cause that? That doesn't feel like a connection issue but rather a component that is in a partial-charged state or a relay that's sticking. Anything like that in the starter circuit?

 

The battery is an always on. It's the ignition power that turns on the radio. I have my ignition power going to a relay like Richard posted that runs to the battery as well.

 

the starter solenoid is a big relay...You may have a loose or bad connection there or a dead spot. On Chevy starters if you didnt get a start in the old days you would tap the starter or the solenoid with wrtench or hammer...just ta[ it snough to free it up not smack it....that indicated a bad solenoid

 

When you pull the ground- you are in essence doing the same thing the reset button is doing.

Simply hook the power wire AND the ignition wire directly to the battery-
-If the radio doesn't work with engine running- bad radio ( very common with some of the Chinese stuff out there- lousy filters/no shielding /bad design)
-If the radio works- the radio can't handle the dirty power- add a relay and you are done.

Starter - that's a whole different subject-

 

FYI...it's rare, but a side post lug-bolt can be tight, BUT the battery cable still is not making solid contact with the battery side-post.
That happened to me once about 20 years ago...drove me nuts until I grabbed the cable where it attaches to the side post and the cable connector moved on the post even though the bolt-lug was very tight.