MH Battery switch

enblethen wrote:
I maybe reading this backward.
My rig uses four pole and the ground goes through the battery control circuitry to delay closing the relay until primary battery had reached a specified level.
If he is replacing a three pole with a four pole then yes, he just needs to provide a good solid ground to the bracket.
If the bad replay is a four pole and the replacement is a three pole, then it will not work.

Again, I have never seen (but I would love to see your wiring diagram for this circuit) an IRD or BIRD circuit that controlled the "ground" side of the cross connect/isolator relay.

I can only reiterate that the 120 series relays are wired and terminated as I have described. The three terminal relays have one end of the pick coil GROUNDED internally.

You can replace a four terminal relay with a three, or vice versa, as long as you totally understand your circuit and know that the relay is controlled by a +12v signal.

All the Intellitec and RV-Custom Products BCCs, IRDs and BIRDs work this way.

BTW - I just looked at your profile and see that your rig is a Pace Arrow. The Pace uses an RV-CP BCC, so your voltage sensing circuit does NOT control the ground side of the relay. It actually provides +12V when the charging conditions indicate that the relay should close. The diagram for your BCC shows that one side of the relay coil goes directly to ground. This means that you could use either the three or four terminal 120 relay. However, the 120 style relay won't physically fit in the RV-CP BCC. Yours, as well as mine, uses an old Ford shaped starter relay. It is continuous duty, though.