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Old 06-25-2018, 07:48 PM   #1
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Interconnect relay energized all the time

My 2000 tradewinds wouldn't start recently because the chassis batteries were flat. The house batteries were reasonably well charged so I thought I could start the engine by using the start boost switch; when I pressed the boost switch the engine still wouldn't crank, the house batteries did not link up. I used a set of jump leads to physically connect the house batteries to the chassis batteries and the engine fired up straight away. I guessed the interconnect relay (large metal cylindrical one behind the circuit board) was at fault so ran some tests; firstly when i touched it it was extremely hot! I has correct voltage from the (now charged) chassis batteries and also from the house batteries, the 12v feed to the relay was showing 12 volts although the boost button wasnt pressed??? the relay was energised all the time and could only be disengaged by pulling the 3 amp fuse next to the small black relay on the BCC board. By removing and inserting this fuse I could feel and hear the big metal relay energising and connecting the two sets of batteries together. I checked the wires to the boost switch on the dash and BOTH showed 12V even when disconnected from the switch???
So, how come the house batteries didn't boost the chassis batteries to start the engine?
How can the two wires to the boost switch both be hot?
Why is there permanent 12V supply to the activating solenoid inside the metal relay?

Any help on this will be appreciated, its driving me nuts trying to find the answer!
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Old 06-26-2018, 12:47 AM   #2
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The high current contacts within the relay are probably pitted and not making good contact. Very common failure mode. Time to replace it.


The control board may be not functioning properly if the relay is hot when no shore or generator or engine alternator power is being provided.


Otherwise It will be on and normally hot to the touch if:
1) your DC converting is working and house battery is at >13.2 volts. for at least some specified time , maybe a minute?
2) engine is running and chassis battery is at >13.2volts for at least some specified time , maybe a minute?
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Old 06-26-2018, 05:18 AM   #3
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Both large terminals will have battery voltage because each one goes to each battery bank. It does what your jumper cable did.

It gets hot when activated. It activates if there is a charging source producing 13.2+ volts somewhere.

When you did your testing, did you have shore power connected, if you did you got false test results.

Engine, generator and shore power off, along with any surface charge, must be off to de-activate the solenoid.

Most likely, as mentioned above, the solenoud is bad. Common problem.
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Old 07-01-2018, 08:58 PM   #4
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hi again and thanks, I have now got a new metal solenoid for the inter connect and will fit it as soon as I can; I'll let you know how it all goes!
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Old 07-12-2018, 10:51 PM   #5
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batter connect solenoid

well, I changed out the inter connect solenoid (not a bag of laughs doing that) and nothing changed! The new metal relay got very hot and no boost interconnect. The only way I could disconnect the interconnect relay was to pull the 3 A fuse, the relay clicked out, cooled down and left me pondering what is going on?? thanking you again for your help and insight to this problem
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Old 07-12-2018, 11:13 PM   #6
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How do you determine that there is no "boost"?
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Old 07-13-2018, 12:07 AM   #7
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Have you checked if your boost switch is shorted or a problem with the wiring keeping the interconnect solenoid energize?

I don't know if your BCC is the same as mine, this is what I have.
If yours is not the same you should call RV Custom Products and ask for the troubleshooting guide for your BCC they will email it to you. They may be able to help with your problem.

RV Custom Products
14000 Anson Ave, Santa Fe Springs, CA 90670
(562) 921-8353
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Old 07-13-2018, 09:04 AM   #8
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Quote:
Originally Posted by the docktor View Post
well, I changed out the inter connect solenoid (not a bag of laughs doing that) and nothing changed! The new metal relay got very hot and no boost interconnect. The only way I could disconnect the interconnect relay was to pull the 3 A fuse, the relay clicked out, cooled down and left me pondering what is going on?? thanking you again for your help and insight to this problem
If you have the coach plugged in,AND the house batteries are reading over 13.2 volts, the BCC will in fact close a relay and power up that solenoid. It does this so the chassis battery will charge from the converter. It will also power up if running down the road and the chassis battery reaches 13.2 volts, so the house batteries will charge from the alternator.

Now if you have replaced that solenoid and it still doesn't work, you have a bad connection some place. To check, unplug the coach, do NOT start the engine, then check for power to the solenoid. Should be none. IF the house batteries are showing over 13.2 volts that solenoid can still be energized. It won't drop out until the batteries show less than 13.2 volts.
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Old 07-13-2018, 09:54 AM   #9
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interconnect relay

i removed the wires from the 'boost' switch and both were live at 12V, so pressing the switch has no effect whatsoever. i guess there is a wiring problem somewhere but I cant find a wiring diagram for that circuit, I only have the BCC diagram (same as you posted, thanks) which doesnt go into detail. On the solenoid there are two wires to energise it, one black and one yellow. The black is ground (testedOK) and I imagine the yellow is 12V live when asked for by pressing the boost switch or the BBC calling for the solenoid to be energised. This yellow wire is 12V live 100% of the time and I dont think it should be. If anyone has a wiring diagram for this solenoid circuit it would help immensely in troubleshooting. Thanks once again!
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Old 07-13-2018, 10:11 AM   #10
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Quote:
Originally Posted by the docktor View Post
i removed the wires from the 'boost' switch and both were live at 12V, so pressing the switch has no effect whatsoever. i guess there is a wiring problem somewhere but I cant find a wiring diagram for that circuit, I only have the BCC diagram (same as you posted, thanks) which doesnt go into detail. On the solenoid there are two wires to energise it, one black and one yellow. The black is ground (testedOK) and I imagine the yellow is 12V live when asked for by pressing the boost switch or the BBC calling for the solenoid to be energised. This yellow wire is 12V live 100% of the time and I dont think it should be. If anyone has a wiring diagram for this solenoid circuit it would help immensely in troubleshooting. Thanks once again!
You need a better reading of the large battery cables then 12 volts.

Each cable goes to a battery bank. One to chassis battery and the other to the house battery, just like you did with the jumper cable.

Measure the exact voltage of each with the solenoid not energized.

Run down the house battery A bit and then measure both battery banks with a digital meter. They shouldn't be the same volts. If they are exactly the same, you have some crossed battery cables, not small wires.

Follow the large cables and see if both go to the same battery bank..
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Old 07-13-2018, 09:12 PM   #11
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Quote:
Originally Posted by the docktor View Post
i removed the wires from the 'boost' switch and both were live at 12V, so pressing the switch has no effect whatsoever. i guess there is a wiring problem somewhere but I cant find a wiring diagram for that circuit, I only have the BCC diagram (same as you posted, thanks) which doesnt go into detail. On the solenoid there are two wires to energise it, one black and one yellow. The black is ground (testedOK) and I imagine the yellow is 12V live when asked for by pressing the boost switch or the BBC calling for the solenoid to be energised. This yellow wire is 12V live 100% of the time and I dont think it should be. If anyone has a wiring diagram for this solenoid circuit it would help immensely in troubleshooting. Thanks once again!
The switch should only pass power when pressed, BUT if the BCC is powering the solenoid, you would have power on both sides of the switch. DC voltage can have power from different sources at the same time. You can NOT trouble shoot this BCC with the coach plugged into shore power. if the house batteries are fully charged, the comparitor circuit on the BCC WILL energize that solenoid when it sees 13.2 volts or more.
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