Wiring A BIM To Battery Control Center

[chuckbear]

I need some info to wire a BIM into the BCC box in my Bounder to replace the auxiliary start and charging relay. Specifically, where to pick up the ignition wire to the BIM and where to pick up the dash switch as shown in the BIM wiring diagram here. Any help is appreciated. Chuck

 

[Gary RV_Wizard]

Your existing isolation relay has those wires - can you use those as the source?

The RVP-Fleetwood Troubleshooting document identifies the posts with the ignition signal and the Aux start switch. I think you have that doc, but I attached a copy just in case.

 

[chuckbear]

Gary, The existing solenoid has a yellow, purple, and black wires connected. Which of these wires go where on the BIM? None of these wiring diagrams that I have looked at give me a clue. Chuck

 

[Gary RV_Wizard]

Gary, The existing solenoid has a yellow, purple, and black wires connected. Which of these wires go where on the BIM? None of these wiring diagrams that I have looked at give me a clue. Chuck

A solenoid has 4 connections, one pair to activate the solenoid and the other pair is the power that is actually switched by the solenoid. Since we are talking about switching battery loads, the switched pair will be the big, heavy duty cables. The other two will be smaller gauge, light duty wiring. Some few solenoids use the metal frame of the solenoid as the activation ground path, so only need one wire to activate. The wire colors are arbitrary.

 

[Gary RV_Wizard]

Per the document I attached previously, The Aux Start switch activation shows at P4 #10 on the RVP BCC board. That would be wired to the SIG terminal on the new BIM

Auxiliary Start and Charging Relay Functions
The auxiliary start relay parallels the coach and chassis batteries in
the event it is desired to start the vehicle with a dead chassis battery.
In addition, the relay controls charging of the batteries as a set.
Refer to fig. 5(Gasoline) and fig. 6(Diesel), Auxiliary Start Relay-
partial schematic, for particulars.
The relay is actuated manually from the drivers console by pushing the
auxiliary start switch button. Coach battery power appears at P4 #2
after passing through fuse F17 and is applied to the dash mounted
auxiliary start switch. The other side of the switch is connected to P4
#10. On gasoline models, P4 #10 is wired to P1 #5 and thence to the
Auxiliary Start Relay. For Diesel models, P4 #10 is routed through fuse
F20 (F22 for rev. C) to P3 #1 before being wired to the Auxiliary Start
Relay. The relay is mounted externally from the Battery Control Center
on Diesel coaches.

Looking at the last page of the document (Load Center Functions), it appears that P5 #4 on the board is the Ignition On signal. I'd wire that to the IGN terminal on the BIM. And BIM GND goes to chassis ground.

Or do it the brute-force-but-sure way:
There will be a terminal strip under the dashboard that has terminals for Ignition On power, Accessory On power, and Chassis Ground. Run a wire from the IGN ON terminal to the BIM IGN. Run a second wire from actual dash switch labeled Aux Start to the BIM SIG terminal.
On my last Fleetwood coach the top of the dash lifted off for each access to the wiring and switches. Yours may not be so handy.

 

[chuckbear]

Thanks, Gary. I will take a look under the dash for the terminal strip. That sounds like the best way to make connections. My dash in front of the driver does lift up. The components of the BCC are 90's technology and for the most part, are no longer available. I am reluctant to be pulling apart the circuit board and wiring only to break something and find it can't be fixed. Doing simple wiring is not a problem for me but I still need to know what wire works what before I start so I don't do something I will very much regret. There is already a solenoid there that does what the replacement BIM will do. Replacing this solenoid is very difficult. I don't want to ever have to do this again. Adding the BIM into the system solves this. There are already wires attached to the solenoid so all I need is to determine which of those wires controls what. My reasoning is the same, I can't afford to do something to harm the circuit board and not be able to find a replacement of have to pay for a very expensive board. Someone had done this already. The current connection is most likely to be that connections that need to go to the BIM are yellow, purple, and black. Others have said, pull them off and see what happens, Easy enough for others to say. The purple wire is also attached to the same lug as a ground wire that is connected to the metal box, which is itself a ground. The yellow wire sits on the upper of the two lugs on the solenoid. The battery connections are not an issue, I know where they are and where they need to be connected on the BIM. P4 #10 and P5 #4 are parts of a multifunction plug that again, I am reluctant to cut into. If I could source these parts from somewhere other than an RV junkyard I wouldn't be afraid to experiment. Again, someone has to have done this already. Chuck

 

[chuckbear]

Gary, you said "Run a second wire from actual dash switch labeled Aux Start to the BIM SIG terminal." Which of the several wires that are connected to the Aux Start Switch would I be running to the BIM? Chuck

 

[Gary RV_Wizard]

Several wires? I can't imagine why there would be several, but in a typical system any wire that has +12v when the switch is closed should do fine. That's the "Option 1" in the BIM diagram.

"Option 2" seems to be switching to Ground rather than +12. I'm not familiar with your Aux Switch wiring, so not sure if that option would apply or not. To be sure, check what the Aux Start switch does when closed, i.e. passes +12 or grounds the circuit. That BIM diagram sure doesn't give any clues as to those two options and when to use one vs the other.

 

[chuckbear]

It's been raining here so I haven't done much since the current solenoid I installed is working. The weather is supposed to improve for the next couple of days so I can do some testing. This should be simple but the BIM manufacturers seem like they want to keep some things secret. It also seems like I am the only one who has ever made this modification since no one is posting any info. I will figure it out. I just don't want to screw up the circuit board. Chuck

 

[Gary RV_Wizard]

I think they just assume that anybody doing that level of repair/upgrade has sufficient knowledge of relays and RV electrical to do it without detailed instructions. It's sort of a self-fulfilling prophecy, right? If you can figure it out and succeed, they must have been right. Or you just got lucky...

 

[chuckbear]

I have done a lot of electrical and electronic installations. I've said this before. This BCC is obsolete and old tech. If I screw up the circuit board in any way, I am screwed big time and in for a very expensive repair. As a result, I am being overly cautious. It's unfortunate that I am the only person in the universe doing this kind of upgrade. Having some advice from anyone with first-hand knowledge would be immensely helpful. Rest assured I will figure it out eventually. Chuck