I cleaned our Big Boy relay about 12 months ago, but it recently stopped working again.
Rather than spend any more time on it I replaced it with a Blue Sea Sytems ML-ACR. This is a simple device that does one thing: connects or disconnects the house and chassis batteries.
The features I like about it are
- will charge both sets of batteries from the alternator or output from the inverter/charger
- auto mode as well as manual off and manual combine override via the remote switch or on the relay itself
- LED status indicator on the remote switch that replaces the Battery Boost switch in the dash/side panel
- takes no current to hold it in either position, so does not run hot
- has high current ratings
- sealed from the elements
- senses charging on either bank of batteries to combine in Auto mode
I had previously replaced the diode based isolator and battery boost relay with the ML-ACR on our 1994 Signature and it operated well.
I have helped Vanwill replace the same setup on his 2000 Dynasty and Mecdatlanta on his 2002 Signature.
In those cases the ML-ACR replaces the isolator, the Battery Boost Relay, and the Lambert style or Trik-l-Amp or Trik-l-Start solution to keep both sets of batteries charged.
For our coach the ML-ACR replaces the Big Boy relay and renders the circuitry that drives the Big Boy unnecessary.
Mechanically the ML-ACR is a similar size as the Big Boy relay and we used 1/8”x3/4” copper bar to connect the ML-ACR to the existing wiring.
We also ran a pair of wires from the RRB to the dash for the remote switch. We could have run one wire and reused the existing wire from the Batt Boost switch.
The switch also needs fused power and ground which we picked up from the FRB.
Before the switch
After the switch
ML-ACR on Amazon
Blue Sea Systems ML-ACR 12V DC 500A Automatic Charging Relay with Manual Control https://www.amazon.com/dp/B001VIXLRO..._DQuYDb6AVKC8Z
Copper bar on McMaster Carr
Many thanks to Mecdatlanta for the help. It certainly helps to have a second person when running wires through the belly of the coach.