My Trombetta failed

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Tom

Tom

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We pulled into our site for the holiday and found we had no 12V from the house batteries. More correctly, after doing some diagnostics, we had no switched 12V from the house batteries.

If you have a house battery disconnect switch near the entry door of your RV, it's a good bet that it switches a Trombetta relay/contactor, which in turn isolates the house batteries from your 12V fuse box. I've never used the disconnect switch, preferring to use the battery isolator in the battery bay, and I've never understood why RV manufacturers bother to install them, especially since they don't isolate all 12V house loads from the batteries.

I didn't have a spare, so I merely bypassed the Trombetta by connecting both the heavy gauge input and output wires to the same stud. All 12V circuits were restored. I'm not sure I'll bother to replace this dumb thing.
 
That's a common problem on Monaco coaches.  Most just bypass the relay, known as the "Salesman relay" :)  It makes it easy for the salesmen to turn the lights on and off with one switch when showing the motorhome.
 
Aye Ned, I've seen salespeople fiddle with that switch. Having it makes zero sense to me, especially since it doesn't isolate all 12V house circuits. FWIW the relay coil failed on mine.
 
When ours failed on the Windsor I told Monaco that should use a "NC" relay not a "NO" (Normally Closed vs Normally Open). That way when the  xxxx thing fails the 12 volts still work. Ours failed while parked by the house. Fortunately Sheila noticed that the refer wasn't make any noise when she walked by the rig (before we lost all the food and had a stinking mess!).

I agree that these are worthless relays, but if they insist on installing them they should be NC so if when they fail the 12 volt power is still on.

I should probably just by pass the one on the Camelot before it has a chance to fail.

ken
 
Aye Ken, NC would be a better choice. I think I'll leave mine "PB" (permanently bypassed)  ;D
 
Tom said:
Aye Ned, I've seen salespeople fiddle with that switch. Having it makes zero sense to me, especially since it doesn't isolate all 12V house circuits. FWIW the relay coil failed on mine.
Click to expand...
On my 2000 Coachmen class 'C', all 12 volts is removed when I throw the switch - and yes, I use it like a saleman might.  When parked at home, I keep the shore power plugged in, but cut off the 12v.  I turn it on to charge the batteries.  The only problem I have is that when switched off, the converter does not supply 12v even when plugged into shore power.  Interestingly, my "Trombetta" has not failed, but one of those automotive type circuit breakers did.  The one that failed was in the path of the energizing ckt for the Trombetta.  The ckbr had a reset button on it (didn't help).  I was unable for find one like it as the only ones available (that I found) were auto-reset.  But, so far so good.
 
Tom, disconnect the coil wires as well.  You can then reuse the switch for something useful.
 
Tom or Ken

So far no problem with our Monaco Trombetta BUT where was the relay located in your Monaco? 

Also, can it be jumped across the Trombetta relay itself or was that what you did by connecting the input and output wires to the same stud? 

Just planning ahead!!!

JerryF

 
Jerry, the Trombetta on our coach is in the front left compartment, inside a large fuse box. It could be jumpered on the relay itself, but I didn't have a sufficiently large piece of wire and large lugs. So, I merely connected both wires to the same stud, essentially doing the same thing.
Edit: Fixed typo.
 
Higher current rating on the contacts does little to prevent the coil failing, which is what happened in our case. I've seen the coils on much higher current rated contactors fail. Ever seen a contactor feeding a DC motor pulling 6000A armature current?

FWIW Our Trombetta feeds a 50A fuse.
 
The advantage (in my humble opinion) of the Intellitec relay described by Gary, and those used in the Battery Control Centers made by RV-CP and Intellitec, is that they are latching relays and do not have long periods of current on the coils.  The coils are activated only when switching from one state to the other (ON or OFF).

The most common failure of this type relay (contactor/solenoid) is tacking or pitted contact points.
 
Some people have used a short battery cable from NAPA or the like to jumper the lugs, but if there is enough slack, putting both on one terminal is all that's needed.  But do remove the coil wires and tape them off.
 
Agreed that a latching relay would be preferable Lou. Could also use a solid state rather than electro-mechanical relay.

Having never used the switch in 6 years of owning this coach, and not having one on our prior coach that we owned for 15 years, and not having one on any of our boats, I'm solidly in the 'no relay preferred' camp. I'd heard of others having Trobetta failures, and should have been smart enough to bypass it long ago.
Edit: Fixed typo.
 
[quote author=Ned]But do remove the coil wires and tape them off.[/quote]

No reason for me to do that. The coil is open circuit, and I pulled the 5A fuse protecting the coil. In our case, the coil wires are safer left in place.
 
Jerry, the disconnect relay is usually in the rear wiring box where the main fuses are located. It was in our Windsor and is there in the Camelot. You can bypass it by either connecting both wires to the same terminal or by using a jumper wire between the terminals. Also pull the fuse or disconnect the power to the coil.

While Monaco did not take my suggestion of using a NC type relay, they did change the wiring a little. The relay on the Camelot only cuts off power to the 12 volt distribution box inside the coach (this in includes power to the multiplex wiring system). But power to the rear coach distribution is not through the relay (nor or the few items connected to the front distribution panel - drivers side front). This means power to the larger 12 volt items are not cut off by the relay - fortunately this includes the refrigerator for those of you that haven't gone residential. So if the relay fails you won't lose your food.

The main house disconnect at the rear box does cut off all house power except the inverter on my coach just like it did on the Windsor.

Gary,
Monaco does use a Big Boy but it is the emergency start relay connecting the house batteries to the starter.

ken
 
For those who have no clue what we're talking about, a couple of pictures:

  • Front driver's side electrical bay. The Trombetta relay and various fuses are inside the black box.
  • Trombetta relay. Note the two heavy-gauge wires connected to the left side, bypassing the relay.
 

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Ken, it looks like Monaco changed locations. On our 2003 Camelot it's in the front driver side bay, along with a bunch of fuses and other relays. You have the upgraded Camelot that replaced the Windsor in the lineup  ;D
 
Thank you Tom and Ken I appreciate your responses.  Now I will be ready if this ever happens to me.

JerryF
 
Did you find yours Jerry? You might want to consider Ned's suggestion and carry a heavy duty wire with lugs that you could use to bypass the Trombetta in the event you don't have sufficient slack in wires.
 
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