Electronics go totally dead after shutting off engine when hot...any ideas?

[2LGT2QT]

It was 110 degrees today. Went for a drive to test the new pusher fan I added to the front of the AC condenser. The car has been overheating on 100+ degree days due to the newly added AC condenser blocking the rad. During the drive today, the new fan kept the water temp to 200 with the AC on high. Since adding the AC, the water temp has been as high as 230 when it's over 100 degrees with the AC on and traffic moving slowly (this was before the addition of the fan today). When running the AC, I have had some problems starting the motor after shutting it down when it's really hot (heat soak?), and need to crank it a bit before it starts.

Anyway, today I shut it down after the drive and tried to immediately restart it...nothing, not even the lights would come on. Battery was fully charged. Waited about 30 minutes and the electronics came on again when I turned the key to accessory. The motor started, shut it down, then no electronics again. Waited 30 minutes, the electronics came back to life and it started again, shut it off, and this time it started again. The engine compartment had cooled off significantly which makes me think there is some electrical component getting too hot and shutting everything down. I included a pic of the fire wall and all the vintage electronics. It's a 65 Coronet that had a 6 cylinder. It has the original wiring with the exception of what has been added for the 440. I've had the car with the 440 in it for 10 years and never had this issue. The real mystery is the fact that the headlights would not turn along with everything being dead.

I'm weak on trouble-shooting electrical stuff so would appreciate any expert advice.

 

[MoparLeo]

Looks nice from what I can see. Can you get a picture of the complete engine compartment. You problem will most likely be at the starter connection. Your wiring looks nice and clean, but if you haven't done this yet, you are not finished yet. Get some good electrical contact cleaner and clean all of the connections and then put a good amount of Dielectric grease on all of the connections before you plug everything back in. This protects against future corrosion and waterproofs the electrical system. Also make sure that all of your grounds are clean and tight. The cooler a wire is, the faster and more powerful the current will flow through the wire. Thicker wires can carry more current with less heat. Think of cheap battery cables that get real hot when you jump a car. The best ones have very heavy cables. Your wiring wasn't designed to carry much load as it was designed over 50 years ago. The modern electrical systems are designed to carry heavy loads, think electronic controlled everything, ignition, fuel, sensors, hd a/c systems, stereo's etc... So the alternators put out 3xs as much amperage as the old systems were designed for. Number one is to fix your cooling system. It should work fine with an a/c condenser if it is working as it should. Things like radiator type, age, width, total capacity. Age of thermostat and waterpump. Is the waterpump made for a/c ? Do you have a shroud ? Proper clutch for the fan blades. Test your radiator cap. Most don't hold pressure and that will cause overheating. get a 16lb cap. Is your coolant clean and a proper 50/50 mix distilled water and ethylene glycol. The modern coolant have corrosion inhibitors designed for modern cooling ayatems which have a lot of aluminum components. They will damage the older cast iron block/heads, waterpump vanes, brass and copper radiators. How did it perform before ? Run warm most of the time ? If your cooling system isn't up to par, the condenser will overwhelm the system. Fans are only useful under 40-45 mph after that the car is moving fast enough that it doesn't need a fan. If it runs hot at higher speeds, you really need to diagnose your cooling system.

 

[Mr Gorsky]

When an old Mopar exhibits symptoms like this, the first thing to look at is the firewall disconnect.

Remove plug, clean terminals, replace.

 

[2LGT2QT]

MoparLeo and Mr Gorsky - thanks to you both. I hope I have the cooling system issues resolved as of today...new pusher fan, new thermostat, 16 lb cap flushed the system, fresh 50/50. I have mechanical/fixed fan off the engine with a tight fitting shroud. Let it idle for 30 minutes in 110 degree heat with A/C on high...climbed to 210 stayed there. The water temp never got above 190 before adding the AC. I will clean all terminals as recommended. Will also double check ground connections. Thanks again.

 

[Yatzee]

It was 110 degrees today. Went for a drive to test the new pusher fan I added to the front of the AC condenser. The car has been overheating on 100+ degree days due to the newly added AC condenser blocking the rad. During the drive today, the new fan kept the water temp to 200 with the AC on high. Since adding the AC, the water temp has been as high as 230 when it's over 100 degrees with the AC on and traffic moving slowly (this was before the addition of the fan today). When running the AC, I have had some problems starting the motor after shutting it down when it's really hot (heat soak?), and need to crank it a bit before it starts.

Anyway, today I shut it down after the drive and tried to immediately restart it...nothing, not even the lights would come on. Battery was fully charged. Waited about 30 minutes and the electronics came on again when I turned the key to accessory. The motor started, shut it down, then no electronics again. Waited 30 minutes, the electronics came back to life and it started again, shut it off, and this time it started again. The engine compartment had cooled off significantly which makes me think there is some electrical component getting too hot and shutting everything down. I included a pic of the fire wall and all the vintage electronics. It's a 65 Coronet that had a 6 cylinder. It has the original wiring with the exception of what has been added for the 440. I've had the car with the 440 in it for 10 years and never had this issue. The real mystery is the fact that the headlights would not turn along with everything being dead. View attachment 509669I'm weak on trouble-shooting electrical stuff so would appreciate any expert advice.

I notice that you have deleted the heater box and associated hoses and if this is the case, consider this. Once you remove that branch of the cooling/heating system you have reduced the volume of coolant in the entire system by about 2 1/2 quarts. This makes a big difference on really hot days especially with a "stacked" set of heat disipaters like the rad and A/C condenser. I think we can all agree that you can heat a cup of water faster than a quart and a minimal cooling system acts the same way. If your air flow through the condenser and rad is adequet with this setup ( usually indicated by the breeze on the backside of the rad) and the spacing between both is correct, then I think it would be safe to assume your cooling system is not large enough to remove engine heat on fairly hot days. I had the same problem and resolved it by installing two (side by side) heater cores ( 3 x 20 x 2 inches thick) down below the rad shroud and almost out of site. I fed them with coolant directly from the engine via the heater tube connections. In "radiant" mode they dropped the engine temperature 10 degrees, with a couple Spal 5 inch quite fans the temp dropped 15 degrees with a 180 stat. In my case, I should have had a larger rad but I had no intentions of cutting my rad support. My engine is a 512/ 630HP and can really crank out the heat under load. Something worth considering because those unused rad taps at the water pump could be used for free cooling

 

[Dennis H]

Bulkhead connector. Did your car come factory with a thermal fan?

 

[2LGT2QT]

I notice that you have deleted the heater box and associated hoses and if this is the case, consider this. Once you remove that branch of the cooling/heating system you have reduced the volume of coolant in the entire system by about 2 1/2 quarts. This makes a big difference on really hot days especially with a "stacked" set of heat disipaters like the rad and A/C condenser. I think we can all agree that you can heat a cup of water faster than a quart and a minimal cooling system acts the same way. If your air flow through the condenser and rad is adequet with this setup ( usually indicated by the breeze on the backside of the rad) and the spacing between both is correct, then I think it would be safe to assume your cooling system is not large enough to remove engine heat on fairly hot days. I had the same problem and resolved it by installing two (side by side) heater cores ( 3 x 20 x 2 inches thick) down below the rad shroud and almost out of site. I fed them with coolant directly from the engine via the heater tube connections. In "radiant" mode they dropped the engine temperature 10 degrees, with a couple Spal 5 inch quite fans the temp dropped 15 degrees with a 180 stat. In my case, I should have had a larger rad but I had no intentions of cutting my rad support. My engine is a 512/ 630HP and can really crank out the heat under load. Something worth considering because those unused rad taps at the water pump could be used for free cooling

Great advice and proven given your set up. Thx

 

[2LGT2QT]

Bulkhead connector. Did your car come factory with a thermal fan?

The motor currently has a mechanical fan. I need to do some research on thermal and clutch fans to understand if they can help with my cooling issues.

 

[Dennis H]

Factory on my 69. I tried pusher/puller with no success and went back to thermal church fan with shroud. Fan locks up with temp increase and does an effective job cooling the 440 even with after market Classic AC running.

Bulkhead connector maintenance is a good idea even if not related to the problem. Carefully remove all banks and spray with electrical contact cleaner. GENTLY reinstall. It was 111 in the shade in my driveway here in San Jose yesterday. Unheard of in these parts.