Add Relay 02/09WARNING THIS PAGE Its not well organized kind a messy. Every time I try to clean up I add more text...hopefully you can glean some info. Simply to turn on or off refrigerator from truck cab
Fig 1 is basic install- as is figure 2 but with addition of switch to turn off & pilot to monitor. Both figs. 1 & 2 involve mounting refer toggle near refer so as not to add to length of main 12v power supply. Fig 3 shows remotely mounting of refer switch which is what I did. This does involve adding a lot more wire, however by adding second relay its not adding to main power supply length.
Warning 2: After this installation I was having intermittent occasions where when truck turned off refer & back on, the refer panel lights were not on. I've since added quenching diodes to relays to bleed off power. It appears the control panel is sensitive to the surge generated when the relays are shut off. The diode is placed between terminals 85 & 86 (not the power in/ out) with the positive (striped) end of the diode to the positive ignition. signal source, the other end goes to relay ground. It is possible to find relays with diodes already installed. This fixed the panel light problem.
Warning 3. Not shown are any fuses-all 12 v sources should be fused.
Warning 4. Generally most automotive switches are rated at 15 amps, insure you get 20 amp min. 30 amp recommended. Our refrigerator uses 17+ amps on 12V
[NOTE if you have Dometic recall safety switches installed this does not affect its intended purpose, new switch and relay are before them-see diagram fig 1].
Added a relay so that when truck ignition is turned off - 3-way refrigerator 12v power is turned off.
Been on the round toit list since the 1st time I killed the batteries. Our refrigerator is a Dometic 3-way. As neither of us are comfortable using the gas on the road, normally when on the road we use the refrigerator on 12v to keep it cold. However when you stop for any length of time the refrigerator will flat kill the batteries VERY quickly. When stopped for more than a few minutes I would go inside and turn off fridge, we'd also try to turn it off like an hour before our destination to insure batteries were fully charged.
That was the plan, don't know how many times we'd arrive with partial batteries- or stopped and forget to turn off or worse when on the road -after turning off Id forget to turn back on. Or thinking we'd only be a few minutes and it'd be an hour. Never failed...just a pain. Neither of us are comfortable using the propane on the road-but lot of folks do. Dead batteries and/or warm milk just don't cut when boon docking
So decided its time to add a relay. Did some research on this but there's just not much out there other than "I did it". Older control boards for the refer actually used to have a terminal for attaching an ignition on source wire. For exactly the reason I'm adding, to save your batteries. I made the mistake of contacting Dometic customer support for possible guidance-what a joke..I have this picture of a lil room in India, or possibly Indiana and depending on which number you dial in on, the person at the other end turns the page in a tattered binder for the appropriate 3 Technical answerers for a given company....
So this is the plan..It a simple one. Just run the 12v from camper batteries to refer thru a relay that is turned on/off by truck ignition. Also add a switch to refrigerator to select whether main 12v goes thru new relay or directly to fridge as normal. Easy yes, but new electronics and pc boards don't actually respond to my mechanical way of thinking. First I don't know if when power is turned off and back on what the refrigerator will do, Be still in the on or switch to off?
So I turned refer to 12v, went outside and disconnected refer 12v source, then reconnected (pretending to be a relay), to verify that when power was disconnected and then restored that refer would still be in the On & in DC mode. I was afraid, like a lot of new electronics, that it would default in the Off mode.
But it didn't-It is still on and In DC mode! Great-I can proceed.
THE PLAN ...Figures 1 & 2
Before starting 1st verify your fridge will still be in the on & DC mode when pulling refer power and reconnecting (pull fuse or disconnect at refer board). If your refer defaults to off when 12v power is disconnected and then reconnected your done, this modification wont work for you.
Figure 2 shows similar approach but uses a 3way switch and added pilot light for more control. Basically disconnect 12v power from refer board, run to new 3 way toggle switch. This will act as selector switch. Switch on positions will determine where power goes, to refer for normal operation or thru relay, which can only happen if truck key is on.
Parts: plug/receptacle, a 30amp min bosh type relay, 30amp toggle switch (w/ screw terminals makes wiring easier) and some 10g wire, 16g wire & female spade, ring &mics connectors. Optional pilot lamp, lighted dash switch.
That's the simple way-Now heres my convoluted approach...
The original plan works [fig 2], IF I would have put switch in refer outside compartment (or maybe a weather proof switch outside), would have been great and only added bout 12" of wire to main 12v feed to refrigerator. (which is what I recommend). But running the extra wire inside added (up & back) about 14'. Its just way too much wire for the main 12v feed. I could up to 8ga but Id rather the main feed was as short as possible. And because of my switching setup I'm kinda stuck. I'm adding another relay that is turned on by the original for direct 12 feed to refer. I just disconnected output from 1st really which is still turned on/off by truck, Ran the out put that went to refer and used it to signal second relay. Then I ran another 12v lead from main block thru second relay to refer. So the main refer feed is now about 12" long. So my install is as shown in [fig 3], I didn't take pics of the second relay but Ill add in the descriptions. As I had already completed install using one relay-adding the second due to length of wire run, made a lot of the 1st install kinda overkill. Like 10ga wire to selector switch then to second relay could have been 18ga. Oh well Its there. You'll also note, now that its been rewired for 2nd relay and direct (short) feed to refer, I can easily bypass either relay, I could also eliminate really A and entire leg from 3 way switch.
As complicated as I made my install, once its done, I can drive stop, leave the truck, get back in and continue down the road- with the fridge running in 12 volts and not worry bout killing the batteries or turning refer on/off. I can monitor/verify the fridge is on and I can manually turn off or to run, the fridge from the truck. With a single switch inside the camper I will be able to set to normal usage or travel usage.
THE REVISED PLAN....
[fig 3] The final install
If access is difficult you COULD run a small 2 wire cable across the front of the camper, drill a hole from the refer panel area down and enter from under camper wing.
NEXT WIRING RELAYS AND SWITCH...
Yup I am putting switch inside camper. This is where the plan changed
This is where we differ. Shown is a single relay which is what most should do. I've a second relay but it does what a single does, its just getting its signal from another relay instead of directly from truck. My toggle switch is inside, but more practical as far as wiring would be to add it here or by refer board.
Again, I've an extra wire because I'm using a 3-way switch. You only need a 2 way on/off. Remote/running switch inside is ok (still Id go 10ga min), because this will only be used for normal gas or 110v electric supply which draws little 12v. It can be used for 12v side but really don't recommend it due to length of wire run, however in a pinch it'll work.
NEXT WIRING THE TRUCK AND SWITCH...
see solenoid page.
Placed the switches so Margaret can monitor and switch. (If you look at diagram [fig 3] there's a lot of duplication. I can rewire at least 3 different ways with what's there by just unplugging/ into different places, should either relay fail or switches, I'm thinking its costing me an amp (2nd relay/extra wire) or so-while on truck side charge circuit for this redundancy. Normal consumption for relay is minimal.