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Old 11-03-2017, 12:11 PM   #1
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Chassis alternator not charging house batteries

MH is a 2016 Leisure Travel Van, Serenity model. As titled, the Mercedes alternator is not charging the coach house batteries when driving. I see a lot of posts on this subject and that same problem exists on my unit. We first started noticing this in the mornings after a couple of days of dry camping and having the low battery voltage alarm go off on the co/propane detector which seems to go off when the battery voltage reaches about 11.8. This was often the case after we made the last cup of coffee and got ready to hit the road. Rather than run the generator just to charge up the batteries, we expected the vehicle to do that job while we drove to the next destination. After a couple of hours of driving, we noticed the house batteries remaining at about 12 volts, with perhaps obtaining a tiny charge from the rooftop solar panel.

I did a lot of Internet searching on the subject including a lot on this website. Then I went out to the MH, removed the cover from the coach passenger seat located behind the vehicle driver's seat. In that compartment I found the components that make the system to charge the house batteries. On my unit there are two separate modules. There is an isolator relay delay (IRD) module manufactured by Intellitec (part# 00-00629-120) and a contactor made by White-Rodgers (part # 586-902).

With my voltmeter, I measured chassis battery voltage on 1 side of the contactor - large terminal. I verified this was chassis battery by running the engine and watching the voltage rise verifying that the Mercedes alternator is doing its job. Then I measured voltage on the other large terminal of the contactor and verified that it was house battery voltage (about same voltage as I see on the control panel). For the small terminals on the contactor, I see one wire going to the ground block strip and the other going to the IRD (red wire). I put my volt meter on the terminal at the IRD red wire and there was no voltage. I clipped the voltmeter on that terminal, started the vehicle, and after about 20 seconds, I heard a snap and saw my voltmeter go to 14.2 volts. With the vehicle running, I measured at the contactor large terminals and I see about 1.2 volt difference between the chassis side voltage and the house side voltage. I think I found my problem. I believe it is a bad contactor since I would expect the voltage to be the same on both large terminals with the contactor snapped closed. Does this sound right?

If have ordered a new contactor and it should be in next week. Instead of a White-Rodgers unit, I ordered a Cole-Hersee 12 volt, 200 amp unit that someone else on a board recommended. I'll give a report when I get this unit in.

I will be taking all the safety steps of disconnecting the Mercedes negative battery connection under the dash and physically removing the ground wire from the house battery. I already verified that operating the house battery disconnect switch does not remove voltage from the contactor large terminal nut. I prefer not to create any sparks or blow any large fuses in this operation. .

Anyone reading this, please feel free jump in... especially if you believe I am not on the right track here. Thanks.
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Old 11-03-2017, 07:01 PM   #2
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Hoosierrun,
You're right on both diagnosing the relay and disconnecting the negative batt cable. I've just finished the same job on my DP.
Hope your repair goes well next week.
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Old 11-03-2017, 10:09 PM   #3
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Quote:
Originally Posted by hoosierrun View Post
MH is a 2016 Leisure Travel Van, Serenity model. As titled, the Mercedes alternator is not charging the coach house batteries when driving. I see a lot of posts on this subject and that same problem exists on my unit. We first started noticing this in the mornings after a couple of days of dry camping and having the low battery voltage alarm go off on the co/propane detector which seems to go off when the battery voltage reaches about 11.8. This was often the case after we made the last cup of coffee and got ready to hit the road. Rather than run the generator just to charge up the batteries, we expected the vehicle to do that job while we drove to the next destination. After a couple of hours of driving, we noticed the house batteries remaining at about 12 volts, with perhaps obtaining a tiny charge from the rooftop solar panel.

I did a lot of Internet searching on the subject including a lot on this website. Then I went out to the MH, removed the cover from the coach passenger seat located behind the vehicle driver's seat. In that compartment I found the components that make the system to charge the house batteries. On my unit there are two separate modules. There is an isolator relay delay (IRD) module manufactured by Intellitec (part# 00-00629-120) and a contactor made by White-Rodgers (part # 586-902).

With my voltmeter, I measured chassis battery voltage on 1 side of the contactor - large terminal. I verified this was chassis battery by running the engine and watching the voltage rise verifying that the Mercedes alternator is doing its job. Then I measured voltage on the other large terminal of the contactor and verified that it was house battery voltage (about same voltage as I see on the control panel). For the small terminals on the contactor, I see one wire going to the ground block strip and the other going to the IRD (red wire). I put my volt meter on the terminal at the IRD red wire and there was no voltage. I clipped the voltmeter on that terminal, started the vehicle, and after about 20 seconds, I heard a snap and saw my voltmeter go to 14.2 volts. With the vehicle running, I measured at the contactor large terminals and I see about 1.2 volt difference between the chassis side voltage and the house side voltage. I think I found my problem. I believe it is a bad contactor since I would expect the voltage to be the same on both large terminals with the contactor snapped closed. Does this sound right?

If have ordered a new contactor and it should be in next week. Instead of a White-Rodgers unit, I ordered a Cole-Hersee 12 volt, 200 amp unit that someone else on a board recommended. I'll give a report when I get this unit in.

I will be taking all the safety steps of disconnecting the Mercedes negative battery connection under the dash and physically removing the ground wire from the house battery. I already verified that operating the house battery disconnect switch does not remove voltage from the contactor large terminal nut. I prefer not to create any sparks or blow any large fuses in this operation. .

Anyone reading this, please feel free jump in... especially if you believe I am not on the right track here. Thanks.
That's a pretty common problem and I think your on the right track. You might try taking the White-Rodgers apart and cleaning the contacts. If you're successful, you've got a spare.
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Old 11-06-2017, 03:26 PM   #4
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OK, I got the Cole Hersee unit from an E-Bay seller, installed it and it appears that it is functioning. The house batteries are charging from the engine alternator at over 14 volts.

I have a couple of concerns though:

1. It appears that the charging voltage remains over 14 volts (14.2 on my digital Fluke voltmeter). Will continuously charging for hours and hours at that voltage damage my house batteries (typical flooded Interstate Golf Cart Style batteries). That assumes I'm driving all day. My house charger, Magnum, goes to float at about 13.3 most of the time when the batteries are fully charged when there are no significant loads turned on.

2. The new Solenoid (contactor) seems quite hot. It is too hot to touch and my clamp-on Amp meter only shows about 38 to 45 amps passing through it. The unit is suppose to be a 200 amp continuous duty, but there was no part # stamped on it, so I am wondering if the heat is normal,... or the seller sold me a lower rated unit. I may try to go back to the original White Rodgers contactor brand to be safe, but the cost is twice as much, and unit failed within a year.

Ultimately, I'd like to put in one of those Intellitec expensive battery command centers, but that is down the road a couple of years, after my vehicle warranty expires. Mercedes currently prohibits a boost switch and an auxiliary method of charging the chassis battery. Only the engine alternator is permitted to charge the chassis battery on these newer Sprinter based units.
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Old 11-07-2017, 10:20 AM   #5
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That's a pretty common problem and I think your on the right track. You might try taking the White-Rodgers apart and cleaning the contacts. If you're successful, you've got a spare.
I spent about 30 minutes taking apart the old White-Rodgers contactor. No joy here. The unit is riveted together. I drilled those out. The contacts were blackened and it was pretty obvious why they were not conducting electricity. To get a view of the contacts you have to break the flex wires. The contacts are recessed into the unit. There is just no way to gain access to get sandpaper or a small file in there. If I could have cleaned the contacts, I would have replaced the rivets with small screws. This unit will have to go in the trash.

The good news is that I confirmed that my new Cole Hersee is a 200 amp continuous duty, and my research found it is normal for them to get quite warm when they are energized. I think my house batteries will be OK. My thinking is that if the vehicle battery can survive being charged at 14.2 all day, the house batteries should be OK too. I did check the water in each cell and added about 5/8 inch of distilled water in each compartment. The water level before adding was about 1/2 inch above the top of the plates.

Anyone with a newer Leisure Travel Van experiencing the same problem, feel free to ask any questions here. If you have a little experience using a voltmeter and some small tools, it is just a matter of finding the location of the contactor and making a replacement (with power disconnected). The bending and a little contorting was the hardest part for me. Also, the least amount of work would be done by replacing the contactor with an exact match (i.e. the White Rodgers unit). I had to relocate some cable clamps due to the terminals on the new unit being in a different physical location (on the side instead of the top).

Happy RVing!
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Old 11-08-2017, 08:29 AM   #6
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Hoosierrun,

Glad that your repair went well. Thanks for great info. My White-Rodgers relay runs quite warm too.

Thanks,
Michael
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Old 11-27-2017, 05:47 PM   #7
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My belief is you dhould slways carry a spare solenoid/contactor as it will fail again. These devices handle a significant current and are inclined to arc at the terminals when opening or closing. Over time this damages the integrity of the contacts and the device fails. In my opinion, it is a critical.device for the enjoyment of the coach. Mine has failed several times and none appear to be robust enough to last forever. As you found they are not difficult to replace. Congratulations and good work!
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Old 11-27-2017, 06:08 PM   #8
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the solenoid will heat up and the voltage will drop as batteries get charged.
Voltage will run between 13.5 and 14.5 for charging voltage.
If you have wet cells make sure you watch the water levels in house batteries.
Here is a link on batteries and charging.
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Old 11-27-2017, 06:30 PM   #9
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My belief is you dhould slways carry a spare solenoid/contactor as it will fail again. These devices handle a significant current and are inclined to arc at the terminals when opening or closing. Over time this damages the integrity of the contacts and the device fails. In my opinion, it is a critical.device for the enjoyment of the coach. Mine has failed several times and none appear to be robust enough to last forever. As you found they are not difficult to replace. Congratulations and good work!
I did purchase a spare. They are really cheap from an E-Bay seller right now. However, I think I will go with a Blue Sea system (7622) eventually. They are rated 500 amps continuous. It doesn't look difficult at all to install (especially in a Serenity). You just take the same precautions that you do when changing the relay.
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Old 11-27-2017, 06:43 PM   #10
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There is another isolation relay, solenoid out there. It comes with a lifetime replacement.

http://www.yandina.com/c600Info.htm
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Old 11-28-2017, 11:00 AM   #11
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There is another isolation relay, solenoid out there. It comes with a lifetime replacement.

Combiner 600 Sheet
Thanks twinboat. That Yandina looks great. It could replace both the B.I.R.D and the relay. .

Michael
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Old 12-07-2017, 08:48 PM   #12
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2. The new Solenoid (contactor) seems quite hot. It is too hot to touch and my clamp-on Amp meter only shows about 38 to 45 amps passing through it. The unit is suppose to be a 200 amp continuous duty, but there was no part # stamped on it, so I am wondering if the heat is normal.
I would suspect most of the heat is comming from the circuit that is holding the solenoid closed and not from the battery charging current passing through the solenoid.


Any idea what circuitry controls this solenoid? is there a switch to turn it off if yo want?
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Old 12-07-2017, 10:16 PM   #13
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I would suspect most of the heat is comming from the circuit that is holding the solenoid closed and not from the battery charging current passing through the solenoid.


Any idea what circuitry controls this solenoid? is there a switch to turn it off if yo want?
Isolator relay delay (IRD) module manufactured by Intellitec (part# 00-00629-120).

There is no manual switch to turn it off. This module is connected to the chassis battery for voltage sensing and to the ignition switch run contact. Two conditions must exist for it to provide power to the solenoid relay coil. Power from the ignition run switch must be present for 30 seconds (to allow for some vehicle warm-up) and the chassis battery must be charging at 13.3 volts or higher.
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Old 12-08-2017, 04:22 AM   #14
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After some dry camping I always run the genny before hitting the road to save my alternator from being overworked. Never break camp leaving the alternator to charge dead house batteries.
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