MH Battery switch

I was not aware than a chassis battery would be charged by the converter. Mine certainly wasn't. At least until I installed a Trik-L-Start. Now it does.

And, yes, I know some higher end RVs do charge the chassis battery from the converter. Most, however, don't.

Sorry for the delay but was in same spot for several weeks and had trouble finding a compatable unit. Finally was able to install a compatable unit (120-105452) a couple of days ago and it still will not charge from chassie battery. Was told that there should be a timer relay that will activate the coil. Was told the relay would be in under dash connected to the emergency start switch. Problem is the wires from switch run from switch to plastic tube that runs under the unit to coil area and there appears to be no relay.
Any ideas?

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.

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.

enblethen wrote:
I just re-read it. Still need to know what kind of circuit OP has as to whether the ground goes through a network to operate. I three posted unit will not work in a four post system.

You need some understanding just to comment on this subject.

He is replacing;

120 105452-6, A solenoid with TWO large posts (for the battery connections) and a single small post for activation of the coil. Total = 3, because the coil is grounded internally.

WITH the following;

120 105752-6, A solenoid with TWO large posts (for the battery connections) and two small posts for activation of the coil. Total = 4, because the coil is isolated i.e. NOT grounded.

I could walk you through the specification sheets for each relay if required.

BTW - I would be very interested in seeing the RV system that uses circuitry to switch the solenoid coil ground.

I just re-read it. Still need to know what kind of circuit OP has as to whether the ground goes through a network to operate. I three posted unit will not work in a four post system.

enblethen wrote:
If there is only one small terminal, it is the power connection. The ground would be through the metal base.
Some rigs route the ground through a monitoring system.
Verify that the old and new relays are exactly the same configuration.

Did you not read my first reply?

If there is only one small terminal, it is the power connection. The ground would be through the metal base.
Some rigs route the ground through a monitoring system.
Verify that the old and new relays are exactly the same configuration.

BJean wrote:
OnaQuest: I have 2 ground wires runing to the single ground on the bad unit. I do not know how to figure out which one should go to witch of the 2 ground posts on new unit. Any help would be of great help.
I appreciate al of the help that I have gotten.

Are you saying that there is only one (1) small terminal on the old unit, with two (2) wires on it?

If that is true, then put both those wires on the LEFT terminal of the new relay AND add a small wire to the other (RIGHT) terminal, connected to GROUND.

If I've misunderstood what you said, please explain.

PS - If the base of the relay is bolted to a metal surface, attach the new ground wire under one of the mounting bolts.

OnaQuest: I have 2 ground wires runing to the single ground on the bad unit. I do not know how to figure out which one should go to witch of the 2 ground posts on new unit. Any help would be of great help.
I appreciate al of the help that I have gotten.