wooslehunter
Active member
I think I know what I'm doing but need to checl from the learned types of this parish.
My charging system is broke (charging at 38V & frying the batteries) & initially I suspected the regulator. The regulator is separate from the alternator & easy to get off so it's off & Ive tested it.
The reg is a CAV Type 440A with the following connections: -, A, WL, F, HI+, MED+, LOW+
So, to bench test, I connect - to PSU -ve, MED+ to PSU +ve. I connect a power resistor from PSU +ve to F.
This is a 24V system & therefore the charge voltage should be around 28V. So I start with the PSU voltage at around 30V. I monitor the voltage on The F (field) pin. As initially this is the supply voltage indicating that F is drawing no current. This is expected since the voltage being sensed is higher tha the regulated charge voltage. I reduce the PSU voltage & at 28.3V, the F voltage drops indicating that F is now drawing significant current. The reg has sensed that the charge voltage is too low & sucks current through the Field winding that would be connected to F.
If I connect to HI +, the switch point happens at 29.5V and LO + it happens at 27.2V.
So, from that, I assume the regulator is working. Next is to look at the wiring (battery + not connected to the reg would give the same high charge voltage result for instance since the reg thinks the voltage is too low) & then the alternator itself (potentially shorted field winding - expensive, hope it's not that).
Am I missing something?
My charging system is broke (charging at 38V & frying the batteries) & initially I suspected the regulator. The regulator is separate from the alternator & easy to get off so it's off & Ive tested it.
The reg is a CAV Type 440A with the following connections: -, A, WL, F, HI+, MED+, LOW+
So, to bench test, I connect - to PSU -ve, MED+ to PSU +ve. I connect a power resistor from PSU +ve to F.
This is a 24V system & therefore the charge voltage should be around 28V. So I start with the PSU voltage at around 30V. I monitor the voltage on The F (field) pin. As initially this is the supply voltage indicating that F is drawing no current. This is expected since the voltage being sensed is higher tha the regulated charge voltage. I reduce the PSU voltage & at 28.3V, the F voltage drops indicating that F is now drawing significant current. The reg has sensed that the charge voltage is too low & sucks current through the Field winding that would be connected to F.
If I connect to HI +, the switch point happens at 29.5V and LO + it happens at 27.2V.
So, from that, I assume the regulator is working. Next is to look at the wiring (battery + not connected to the reg would give the same high charge voltage result for instance since the reg thinks the voltage is too low) & then the alternator itself (potentially shorted field winding - expensive, hope it's not that).
Am I missing something?
