Your new pickup and new 5w

[traveler2955]

You may set yourself up to fail if…. here’s a warning.
Recently, we purchased a new 5w and in the process had the RV company connect a “charging relay” to the new Chev Silverado.
This relay disconnects the pickup when the key is turned off from the RV, because without the relay one might discharge the batteries in both units. Furthermore, a pickup might discharge due to leakages from gunk buildup in the plug or grounded loop in the wiring. (Really, I keep things clean, but….)
The problem:
A couple of months later our engine light came on indicating an issue, whereby I took the PU into the auto dealer.
The find:
The relay did not have a diode in the circuit and was back feeding into the computer and digital information center in the pickup. That ruined the computer and the digital information center (the dash instrumentation). Additionally, the relay was dangling off the fuse box, and it wasn’t of sufficient capacity for much but the RV.
The solution: A new computer and information center was installed along with a properly mounted, heavy-duty relay, the system tested and computer reset.
Causes and effects:
While I was lucky, in monetary terms that is, new pickups might have similar electronic circuits. In fact, says the dealer, placing a smart phone or IPAD type unit on the passenger seat could light the passenger airbag and, you can guess what happens next. The more sophisticated we get in our rigs, the more we need to know, eh?
So, one might want to consider proper wiring and equipment before any installation, but how would a consumer really know? In this case, that’s a $2,000 or more question if one gets it wrong.
Although I’m not angry at the RV facility, they simply did what they did for years, imagine what would happen if your tow didn’t function properly and you were in an accident? Then again, maybe you purchased an out-of-warranty rig, or if your dealer wasn’t so generous. The RV dealer now knows, I hope you consult your dealer first.
Good luck,
Mike

[acadianbob]

And I wonder whether you really needed that mod? I know that our Ford automatically disconnects itself from the trailer when we turn the motor off. You would think that all brands would do that?

[EdJunior]

Originally Posted by traveler2955

In fact, says the dealer, placing a smart phone or IPAD type unit on the passenger seat could light the passenger airbag and, you can guess what happens next.

Uh, I would sure like to know how this might happen. Since the airbag is designed to deploy on an impact, I just can't see this.

As for the relay and such, I know some of the earlier Fords would come with the wire to plug in the fuse box that would allow the truck to charge the trailer. It was not typically not installed by the dealer, I could only assume because he didn't know who would tow something that needed charged or not. But I didn't have to put it in my new truck. I wonder if they finally just started doing it on all the trucks.

[Rod Johnson]

My truck and trailer are electrically coupled as long as the trailer plug is plugged into the hitch plug... ETA, well, they are now. I pulled the underhood fuse box cover off, bolted the loose ring terminal onto the fuse protected stud, installed said fuse, and then plugged the trailer brake wires together that GM leaves unplugged

And people swear up and down about battery isolators and making sure both batteries are new and the same brand and capacitance or they'll discharge each other. I've never had a problem.

How big was your solenoid/relay? There is a 40A fuse in the Chevys on that charge line.

And how does backfeeding 12 to 14 volts into your trucks charging system from the trailer, especially when the alternator is doing the same thing in pretty much the same spot, cook your computer and DIC?

Yes, there is a switch in the passenger seat that detects a human sitting in it. If you were involved in an accident that would trigger the airbags, but the truck didn't detect somebody in the passenger seat, it would not deploy the passenger side airbag. It was designed to reduce the costs associated with repairing a vehicle after an accident. You can of course manually turn off the airbag deployment if you carry a laptop, or your dog, or a child in a car seat in the passenger seat... Setting your phone in the seat isn't going to set off your airbag...

It was awfully nice of your dealer to warranty your truck... Even though they blamed it on some aftermarket wiring...

[Rod Johnson]

Originally Posted by acadianbob

And I wonder whether you really needed that mod? I know that our Ford automatically disconnects itself from the trailer when we turn the motor off. You would think that all brands would do that?

The newer GM trucks don't disconnect from the trailer automatically. I leave the trailer on shore power, and it keeps my truck battery charged, too.

[traveler2955]

What can I say, except, the situation could have cost us a bunch, and we were certainly lucky?

Other than those details I shared in the post, I'm uncertain about the relay specs or the diode capacities.

The post wasn’t / isn't a gripe, just for one’s information and a shared comment.

Good luck to all,

Mike

[RubenZ]

Hmmm. I'm new to this whole RV thing and I have a 2007 Classic Chevy 2500HD. Do I need to do this mod? I sometimes leave trailer plugged into truck especially if we are just stopping through the night.

[Rod Johnson]

I haven't unhitched my trailer since I bought it...

I leave it connected to shore power to keep the truck battery topped up

[traveler2955]

RubenZ,

I'm certainly no expert, but it seems to me that a leakage anywhere would eventually cause a discharge in the batteries of your tow. Exactly ow much depends on many factors. For example, it depends on whether you do a lot of boondocking where you are not plugged into shore power.

A quick example of leakage is the case of your battery, where measurements taken on a grimy battery show depleting resources. Of course, it may not matter if you use your vehicle a lot and the alternator keeps the cells at the proper level, or you’re plugged in each evening as some folks are.

I suppose, because I’ve been sailing the ocean for 4.5 years on our own sailboat, living on 12 volts continually except for a marina here or there, a fully discharged battery complement worries me. Not only must I charge the system when I needed it most, but batteries that are more than 50% discharged are damaged. I always tried to keep my system up past 75% full, and was successful at least 98%, hence the relay.

Grounded loops, or shorted circuits are the result of moisture mixed with stuff, like dirt and grime, which interacts between electrically energized wires. These loops cause noises on telephone lines, noises on our amateur radio equipment, buzzes in your car radio as you travel around, and of course, corrode the connections and the wires themselves.

I'm sure I should have checked the quality and sizes of the relay and inspected the connections, but we all make an error at times don't we? In fact, I probably should have done the job myself to be sure.

For me, the cliché, an ounce of prevention is equal to a pound of repair, seems relevant. The answer to your question, therefore, is: I don't know, that's a call for you.

Mike

[flyrotor]

I have never had a battery isolator installed, I have never had an issue with discharging my batteries when I didn't expect that I might.

If I am running a lot of power and my trailer is plugged into my truck, and my truck is sitting idle (not running) I can expect to run ALL the batteries dead.

It's quite simple and costs nothing to unplug my trailer from my truck. If I had a motorhome with coach batteries and truck batteries that would be different, I can see needing an isolator in that situation.

I think the dealer sold the original poster something that he didn't "need" in the first place. Too bad that it damaged your truck.

[onthefence]

Originally Posted by Rod Johnson

And how does backfeeding 12 to 14 volts into your trucks charging system from the trailer, especially when the alternator is doing the same thing in pretty much the same spot, cook your computer and DIC?

The diode in a relay is for transient voltage suppression, when you drop power to a relay a voltage spike ensues. Voltage spikes of up to 100v are common, it can and will kill electronics.

[Rod Johnson]

Originally Posted by onthefence

The diode in a relay is for transient voltage suppression, when you drop power to a relay a voltage spike ensues. Voltage spikes of up to 100v are common, it can and will kill electronics.

We don't feed trolls around here...

[LadyWindrider]

ONTHEFENCE is correct, and I have the electronics degree to prove it. When the voltage collapses on a coil, (as in a relay coil), a reverse voltage spike is generated, and can damage electronics. A diode place across the coil, in the proper orientation, will short this spike out, and no damage will occur.

Now as to why the dealer installed relay caused damage, we have no proof, just the dealer's word. We also don't know what 12 volt wire he hooked the relay to. I can only assume it was one that was tied to the computer somewhere. Dealer should have corrected and cut the poster a break, but that is his battle to fight, not mine. As for sloppy install, (relay hanging), again his battle to fight. And yes, the Ford trucks have had this as a factory option quite a while, as long as you got the towing package, not sure if Chevy or Dodge has caught up or when. Don't evetyon chime in on the last statement please, let's stay on topic.

[onthefence]

Originally Posted by Rod Johnson

We don't feed trolls around here...

Wow, now thats a warm welcome.

[Herk7769]

Originally Posted by Rod Johnson

We don't feed trolls around here...

I don't understand this comment or how it applies to this thread.
Please explain.

Also, I also don't understand why the OP's original dealer installed a relay to disconnect the camper when the truck's key is turned off on his Chevy truck.

The charging circuit line is already relay protected (in the engine compartment fuse box) through the ignition circuit. In my 2008 GMC Sierra, the ignition key must be in ON/RUN to get juice on the charging line to the socket.

[Rod Johnson]

Originally Posted by herk7769

I don't understand this comment or how it applies to this thread.
Please explain.

I jumped the gun and made some assumption that may have been in correct. I do apologize.

On a side note, having spent the last 18 years as an Electronic Technician and Technical Manager repairing and maintaining video games, as well as several years as an installer doing car stereos and alarms, I might not have the theory down like you guys, but I have plenty of experience on the practical side dealing with these issues.

I question how the noise of a relay on the power side took out his logic boards. There is a pretty big coil in the starter solenoid, ton of coils in the relays for the fans, light, foglights, AC. Not to mention how dirty the power coming from that alternator is. Yes, you can see the voltage pike on an o-scope, but put that relay into the real working world, right next to the battery (and all of its capacitance) and let theorize about how that killed his BCM or PCM.