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Old 05-12-2011, 08:39 PM   #1
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Isolator relay question

I have a question for the experts. I suspect I may have a problem with the isolator solenoid again. I started the coach today for the first time in two months. I used an external charger on both battery banks about a month ago. Ran engine for a little more then 5 minutes today and the solenoid failed to connect the house batteries in that time.
Heres my question. If the coach has been sitting for over a month ( which means the engine batteries will not be fully charged) will it take longer then a minute or two for the relay to connect the batteries so the house batteries can receive a charge? I understand that the engine batteries must reach a pre determined voltage before the circuit will close but I have never known it to take longer then 5 minutes as it did today. My second question is >>> while the alternator is charging the engine batteries ( and the batteries are still isolated) is there something that prevents me from manually connecting batteries with the booster switch because I tried this and it did not connect the batteries. Me is thinking my isolator is toast again for the third time. Any second opinions out there?

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Old 05-12-2011, 08:58 PM   #2
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My 08 knight most likely is a mechanical clone of your HR. I've noticed everything you have mentioned. On more than one occasion, it has taken a considerable amount of time while driving down the highway for the BIRD to close. I monitor the house voltage with a digital meter plugged into a lighter socket on the dash, and always run with the intverter on, so I check.

Those times when the DVM did not indicate the house batteries charging, hitting the boost button did not change the meter reading.

It is on my list to verfify the boost button works, but not quit sure the best way to do it.

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Old 05-12-2011, 08:59 PM   #3
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Have you checked for 12V power to the solenoid (relay).....power that activates the internal coil. If no power check for a bad fuse ....I think it's a 5 amp one on my coachIf you have power to the relay then the coil should be energized and the banks should then be connected. The way I would verify if the banks are actually being connected is to remove the battery cable from one side of the relay and then check the relay lugs for continuity when the coil is energized.
Back to your original question about the booster switch.......assuming you're trying to charge both battery banks then IMO a better way is to connect positive on one bank to positive of the other bank with a 10gauge or larger wire........ If you're not moving the coach you can use alligator clips but if moving the coach you should bolt the wire in place. Don't forget to remove the wire before you use the coach to prevent draining ALL your batteries. If in fact you need to replace the isolator solenoid again I suggest you use a Cole-Hersee solenoid with silver contacts for longer life. luslighthouse.com carries them. Good luck
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Old 05-12-2011, 10:12 PM   #4
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Jim your post gives me hope. Tomorrow we are taking the coach out for the weekend ( one hour drive) so hopefully solenoid will do its job. Kix I have not checked anything at this time however tomorrow after setting up at the campground ( assuming problem still exists) I will get out the tester and see if there is power to the solenoid. I will post results tomorrow. Thanks for the replies..
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Old 05-13-2011, 09:16 AM   #5
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You said the engine ran for a little over five minutes and did not connect.

IDLE or Highway speeds? (This is important)
State of charge on CHASSIS battery (may be important)

There are basically two types (Well 3) of isolator 2 are relays (the 3rd is the diode type, it's always connected)

Type 1: Timer. Is controlled by the ignition switch, There may or may not be a delay (I hope there is. You crank her up and 1 minute later it connects (or however many seconds it's set to)

Type 2: Intellegent: This type measures voltage and if the SOC on the chassis battery is low, it won't connect till the chassis battery comes up to spec. At full idle this may never happen.
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Old 05-13-2011, 01:25 PM   #6
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Monacoach is that a B.I.R.D system in your MH?
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Old 05-13-2011, 03:24 PM   #7
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The relay for the Aux start (boost) may be powered form the house batteries, so it may not be able to close when the house batteries are near dead. The solenoid needs 12v power to work, and the presumtion on that switch is that the house batteries are good and the chassis battery not. yours is the opposite. You could always manually connect them with a jumper cable, though.

If the chassis batteries are very low, it is going to take more than a few minutes before the house batteries begin to charge. Or at least it does on mine, but my system is different than yours.
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Old 05-13-2011, 04:12 PM   #8
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No its not a bird.. Drove half hour on highway, and hurray the solenoid kicked in.. I guess the chassis battery needed a good charge..... now I know... thanks guys....... now on to my next problem.... got to campground and front TV wont power on...... oh well I wont hijack my own thread with that one... I better go do a search....

thanks for the help

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