Blue Sea ML-ACR Questions

[gksmith]

I have installed a Blue Sea ML-ACR Automatic Charging Relay in my 2002 Leisure Travel camper van per suggestions on this forum. But I obviously do not understand how to use it properly. I dry camped for several days, confident that my engine battery was isolated from my coach batteries. But when I went to move to a new location, I discovered that all batteries were essentially dead--at least too dead to start the van. Upon investigation, I found that I had improperly connected all batteries together by latching the center button. Obviously, I did not properly read the instructions. But, what led me to this error was seeing that the only way that I could get the engine generator to charge the coach batteries was to have the center button in latch position.

Upon having the dead engine battery problem, I did more troubleshooting and have verified that the only way I get charging to the coach batteries from the engine is to have the button latched. There is no difference in the voltage being delivered to the batteries in either A or B position, which was the same voltage with the engine not running, 12.7 volts. With the engine running and center button depressed, the coach batteries received 13.8 volts.

Hence, my question--What am I doing incorrectly? How do I get a charge to the coach batteries without having them connected directly? I do not have the external remote switch connected, as I did not feel that it was necessary in my situation. And, I verified earlier with the company that it was not necessary to install the switch. Please help!

Thanks in advance!

[Gryphon]

Do you have the black wire from the wiring harness connected to ground? You need to do that even if you're not using the external switch. Without that connection, the relay can't measure the voltages on the two main power terminals and won't be able to tell if you're charging or not.

Also, you realize that there can be a delay of up to 90 seconds after starting the engine (or starting the generator, or connecting to shore power) before the relay automatically closes?

Edited to add: I assume that this is the relay being discussed.

Also, there's this note in the FAQs for that relay:

Q: Can I ground to the chassis when installing in a vehicle?

A: Run the negative wire for the ACR directly to the battery negative terminal of one of the batteries. A chassis ground is often insufficient to allow proper operation.

[booster]

Assuming you have the full automatic ACR with yellow manual override on the ACR itself and a 3 position remote switch?

You should never need to use the remote switch unless you are locking out the ACR for safely to assure no downstream power, or if you need to lock it in position because the coil has failed.

I would agree with the possible ground issue.

When you have charge level voltage on either side and the remote switch on Auto, there should be a delay and then a noticeable "clunk" when the unit engages. You should get the same clunk, engine running or not, when you turn the unit on and off with the remote switch. If you can't hear it actuating, there likely is some sort of wiring error in the control side, or the unit is bad (highly unlikely as Blue Sea stuff if very nice).

These are very nice ACRs, we have used the manual only version with remote switch for years now with no issues. Very convenient to be able to control on and off from the cockpit, and in your case also be able to just let it do it's thing.

[gksmith]

Thanks for the information
I checked and there is not a ground wire being used. I assume that the black wire of the cable bundle for the remote switch is the one to use and it can/should be connected to the engine battery.

I am on the road right now but will make the change ASAP. I will let you know the result when I make the change. Thanks again!

[RT.SS]

Originally Posted by gksmith

Thanks for the information
I checked and there is not a ground wire being used. I assume that the black wire of the cable bundle for the remote switch is the one to use and it can/should be connected to the engine battery.

I am on the road right now but will make the change ASAP. I will let you know the result when I make the change. Thanks again!

There is your problem; the black wire from the cable bundle needs to be grounded preferably directly to the battery negative post. Only the yellow and red wire goes to the remote. You need to “add” a ground wire to the remote switch ground terminal, only if you plan of using it.

The remote switch is handy to have and used it all the time. With the remote, I have the ability to manually disengage/lock the relay if needed. I usually lock the relay when chassis uses significant power to operate during specific conditions, ex. during cold starts where glow plugs are active, during DPF regeneration process, or when chassis battery is low and pulling a lot of charging current, this is to minimize excessive load to the alternator-probably not a concern but it’s just me. I also have solar, so I let the alternator bulk charge the coach battery, then disengage it and let solar do the finishing charge.

[gksmith]

I am a great procrastinator, but with an upcoming excursion, I finally wired the black wire to the engine negative battery post and the unit now works! But I do have a related question. When the center of the ACR depresses automatically, there is charging to the coach batteries as expected. However, manually pushing and engaging the center button is how I previously charged the coach batteries. This seems almost identical. Am I correct in assuming that when the center button is engaged automatically by a voltage differential, disengagement will take place automatically when needed, whereas, when the center button is engaged manually, disengagement does not take place even if needed to protect the engine battery?

One final question--one reason I did not install the remote switch is I did not know how to mount the switch. Is there an available housing that the switch could be surface mounted in the cab? Else, how does one mount the switch?


Thanks again for the help that you all provide!