Replacing a Parallax 7355 RV Power Converter

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The first thing I learned when I became an RV owner was that pretty much everything will need to be repaired or replaced, and usually sooner, rather than later. 

The second thing I learned was that most RV makers don’t tend to hire the “best & brightest” engineers.

Case-in-point, our Forest River travel trailer had a completely useless water filter built-into the very back of an almost completely inaccessible bathroom cabinet (we use an external filter, so this was redundant). We didn’t even know it was there until it started to leak.

About Bad RV Engineering & Design

You’d think that the manufacturer would have placed the filter below anything that could be damaged by water, since it’s all but guaranteed to leak at some point, but no… They installed it directly above the trailer’s Parallax 7355 power station. So, when it began to drip, there was an immediate arching sound, and I raced outside to cut the shore power.

Wouldn’t it have made (a lot) more sense to put the water filter below the electric panel, maybe with a drip pan beneath it?

I digress.

We got the leak fixed, put a fan in front of the power center for a few hours, and crossed our fingers as I reconnected shore power.

Nothing blew-up! In fact, it seemed as if everything was back to normal.

A couple of weeks later, though, as I was still cursing the Forest River engineers who’d designed this thing, certain that none had graduated top of their class, my wife pointed out that the house lights “seemed dimmer” than usual. “Seemed dimmer” is a pretty subjective thing. I couldn’t really be certain, but I guess, yeah… A part of me thought they were dimmer, too.

The next day, I checked the batteries with my VOM, and sure enough, both were on death’s doorstep.

Next, I downloaded the troubleshooting guide for our power center (a Parallax 7355), and about two minutes later, confirmed with certainty, that arching I’d heard was the built-in power converter bidding us farewell.

The Difference Between RV Inverters & Converters

When I started asking around among friends, I learned that a lot of folks don’t really understand the difference between an RV power “converter” and a power “inverter.”

A “converter” converts the high voltage AC (shore power) coming into the RV, down to low voltage (DC) “house power.” In most cases, that converter also charges the (house) batteries.

On the other hand, an “inverter” does the opposite. It inverts (increases) the low voltage (house) power up to high voltage AC, allowing you to run things like your TV or microwave off the batteries when you’re not connected to shore power.

As is the case with many (most?) RVs, ours does not have an inverter.

It’s our converter that needs to be replaced.

Replacing an RV Power Converter

The converter is the lower section of the Parallax 7355 power center

I looked around online to see if I could find a replacement power converter and came-up empty.

I called Parallax support, which, by the way, was outstanding. Their support line is actually staffed by the engineers who designed their products, so confidence was high when the guy told me the 7355’s converter had been discontinued, and  the newer 55RU is the direct replacement.

A couple of days later, the 55RU arrived, and just in the nick of time. The batteries were almost completely dead.

Replacing it was a real pain, but not so much because of anything technical. Forest River put this thing in the least accessible place they could find. As a result, the job took about 2 hours, and that was 2% skill, and 98% contortion.

I thought my last RV project, replacing the RV’s original microwave, was an exercise in awkward positioning, but that was nothing compared to this.

If Forest River had installed the thing in a more logical place (oh, say above the water filter, or better yet, at eye level), the job wouldn’t have taken more than 30 minutes.

The instructions for replacing the converter were, for the most part, pretty straightforward.

Ready to install the new converter. 

The job consisted of disconnecting the shore power & the batteries (in my case, two 12v flooded deep cycles wired in parallel), removing the cover over the breakers, pulling-out the DC fuse block, and then reversing the steps to install the new one.

The old power center, with the new RU55 converter installed 

In the end, it worked perfectly, and we’re back in business.