Installing AV Receiver in Class C

[Kerry]

We have a Class C Thor Freedom Elite (2014) which we enjoy. I just finished replacing my stereo (AV receiver in the dash) and thought others might want to achieve the same end result.

It came with a double-DIN stereo mounted in the usual location in the Ford truck cab. I was never happy with the way it was wired and it was an older unit that didn’t have some features I wanted, so I bought a new Sony XAV-AX5000 from Crutchfield. But these stereos are designed around the way cars and trucks work and it’s not simple to wire it so that you can listen to tunes or watch videos when camped. Crutchfield was no help.

Here are my requirements:

1. When camping, don’t allow the stereo to drain the truck battery
2. When camping, there must be a way to reduce the power consumed from the stereo when you don’t need it. Doesn’t matter when you are on shore power or running the generator, but sometimes you want to conserve the house battery
3. Don’t lose the settings when switching from one mode to the other. On the Sony, losing the settings puts the device into an annoying demo mode, and you lose things like the backup camera driving lines.
4. Nice to have - if the house battery is turned off but the truck is running (as in driving to your storage site) the stereo should work

You can’t really meet all these with just wires, you need a relay to switch things from “driving” mode to “camping” mode. The attached schematic shows how I connected things to make it all work nicely. I connected all the bits on a very small proto panel, covered the wire side of the panel with a piece of plastic and then soldered it to the wires coming from the the two connectors (truck-side and stereo-side). Then I stuffed it in the dash behind the stereo with the various wires.

In my RV the house power comes to the dash from the main 12V fuse panel (in the rear of the RV) via a 15A “audio system” fuse. When the house battery is switched off (storage mode), this voltage goes away. Whether the previous owner or the factory installed this wire I don’t know.

When relays switch, the contacts bounce - rapidly turn on and off for a short period of time. I was concerned that during this bounce period the stereo would be completely powerless and lose the settings. So I added a capacitor that can provide some current during the time that the system is switching from truck to house battery, or the reverse.

Like most aftermarket car stereos, there really isn’t a way to turn off the Sony. It’s designed to go into a very low power mode (~1ma, I measured) when the ACC (red) input wire goes low. So in order to meet requirement #2, you must install a toggle switch somewhere otherwise it will always draw power - even if you turn off the display. I drilled a hole in the dash and put a black toggle switch there lit with a blue LED. The previous stereo installer connected the house power to both the red and yellow wires on the head unit, so the unit had no way to go into low power mode.

The pin numbers on the schematic are for an NTE R14-11D10-12 relay that I bought on eBay for $5. You can get any 12VDC coil DPDT relay for which the contacts can support the power consumption of your unit. The Sony has a 10A fuse which matches the rating of the NTE relay. I added a 1N4001 diode (super common and cheap) to absorb the reverse emf when the relay switches off, but it might not be required.

I got a 33,000uF / 25V capacitor on eBay for around $10, don’t get one with any lower voltage rating. I picked this value because its physical size is about the same as the relay. It works fine for the Sony, but depending on the details of the way that your stereo and/or relay works you might need more. Or quite possibly a smaller (or even much smaller) cap would be fine, I didn’t test a smaller cap. Or maybe no cap is required at all.

If you have a second house wire that is always connected to the battery **and is fused in such a way that it’s easy to replace the fuse if necessary** and is of the correct gauge for the distance to the stereo - then you don’t need anything other than the toggle switch. I don’t have such a wire. Of course if you forget to turn off the stereo with that switch when you put the RV in storage then it will promptly drain the house battery. With the relay the stereo is guaranteed to be in low power mode when the RV is in storage mode and the truck is turned off.

Others may have already come up with good ways for AV head unit installs, I couldn't find such a link but if they are there I'm sure some clever reader will point them out to me!