I started this topic in another message thread and decided to move it here where it belongs.
Here is the original post
Right now I am spending my spare time struggling with an electrical problem in my old 68 Chevy and I'm going to go waaay off topic because I think htat you may be able to help me.
There is a problem with the starting circuit that I haven't been able to correct. I'm getting a large voltage drop between the battery and the starter solenoid that comes and goes. For years it would occur only when the engine was hot and then recently it failed altogether. I went through the circuit replacing switches and cleaning up connections and now it is back to a hot engine problem or at least it seems that way at the moment. In the past few weeks it has been failing randomly both hot and cold as if it has an intermittent connection but I haven't been able to find it. It is very hard to find because it is not consistent.
In addition to the possibility of an intermittent connection it has been suggested to me that the problem is that the electromagnet in the starter solenoid is getting hot causing the resistance in the wire windings to rise and causing the solenoid to fail to energize. When I put a volt meter at the solenoid when the problem occurs the voltage is about 8vdc which is a 4.5vdc drop from battery voltage and not enough to energize the solenoid. If it is true that the resistance had risen in the solenoid due to heat wouldn't I see less of a voltage drop due to less of a load created by the solenoid? When the system is operating correctly the voltage at the solenoid is about 10 - 10.5 volts.
Mike.
Here is the original post
Right now I am spending my spare time struggling with an electrical problem in my old 68 Chevy and I'm going to go waaay off topic because I think htat you may be able to help me.
There is a problem with the starting circuit that I haven't been able to correct. I'm getting a large voltage drop between the battery and the starter solenoid that comes and goes. For years it would occur only when the engine was hot and then recently it failed altogether. I went through the circuit replacing switches and cleaning up connections and now it is back to a hot engine problem or at least it seems that way at the moment. In the past few weeks it has been failing randomly both hot and cold as if it has an intermittent connection but I haven't been able to find it. It is very hard to find because it is not consistent.
In addition to the possibility of an intermittent connection it has been suggested to me that the problem is that the electromagnet in the starter solenoid is getting hot causing the resistance in the wire windings to rise and causing the solenoid to fail to energize. When I put a volt meter at the solenoid when the problem occurs the voltage is about 8vdc which is a 4.5vdc drop from battery voltage and not enough to energize the solenoid. If it is true that the resistance had risen in the solenoid due to heat wouldn't I see less of a voltage drop due to less of a load created by the solenoid? When the system is operating correctly the voltage at the solenoid is about 10 - 10.5 volts.
Mike.