Furnace A/c relay clicking ?

Mr Bee · 11-09-2019, 11:27 PM

Hello all,
I been trying to search this for several hours and cant find a similar issue.
We have a 2019 SLX 265.
Roof A/C and propane furnace with Dometic thermostat wall mounted.
The A/C worked fine all summer.
The furnace is having an issue. Just before it comes on we hear a lot of clicking from what i assume is a relay, in the roof mounted a/c. About a month ago we used the furnace a few times and sometimes that relay would click a ywhere from 2 _ 6 times then the furnace would fireup and work fine. When shutting down it would click a few times.
Now we are using the furnace ever day and each time , before it lights the clicking just goes nuts. Clicks many times 15 - 20 times then once furnace is fired up the clicking stops until it is shutting down then same clicking.
As I said the clicking is in the roof a/c area not down under cabinets where the furnace is. I understand they are wired together through the Dometic wall mounted thermostat so what relay or whatever in the system could be doing that and why ? The furnace heats just fine.

Thanks for any thoughts on this.
Brian

**JFlightRisk** · 11-10-2019, 12:16 AM

We don't have a Dometic thermostat, but have you got it set to heat, and the fan OFF the auto setting?

Mr Bee · 11-10-2019, 03:09 AM

Yes, set on heat only and pretty sure we have the fan off. I will check when i get home after work to make sure.
Thanks.

Mr Bee · 11-10-2019, 05:57 AM

The settings are * Furnace * * Cool* and the fan settings. The fan settings are Low , High, or Auto, there is no off for the fan. You select the fan setting then Cool or Heat. In low or high fan the roof a/c fan will stay on all the time in the low or high setting. On Auto the fan only comes on when the a/c is on.

Sassy · 11-10-2019, 09:16 AM

I’d remove the roof top cover on AC h it and check the connections coming from thermostat and those going to furnace. The two blue wires are the control leads that run down t9 the furnace control module from the air conditioner electronic control module

The clicking you are hearing is most likely one of the solid state relays on the roof AC control board.

Both AC and furnace are tired together via this board and thermostat is wired into the AC control module on the roof..

I’d also ... with power removed reseat all plug in connections on the AC control module...

Be advised that DC power is constant up to the roof AC control module all the time as long as battery and or shore power is connected

Mr Bee · 11-10-2019, 12:39 PM

Thanks for the response. I will check those out as soon as i can.

Mr Bee · 11-10-2019, 01:57 PM

Looking up from the inside there is a grey plastic bix that all the wires run into. I assume this is the relay.
That is the source of the clicking.
Just to be sure,I pulled to cover on the roof top and listened for the clicks. Nothing there so went back inside, disconnected all the plugs and pushed them back in.
Twisted the wire nuts a little more to make sure they are tight.
Cycled the furnace on and off a few times and at most there was 2 clicks .
When it gets cold again we will see if it was just a loose connection or if I need a repair person to come have a look.

Thanks for the suggestions.

Jolvi · 11-13-2019, 08:46 AM

Had the same issue with our 22RB first night out we stayed in campground at dealers location for free. They do this as a courtesy in case there is an issue. It was a bit cool and seeing as how we only had a 76 mile trip did not take anything but sleeping bag in truck. Turned on furnace it worked great the two times it came on, on the third time it did the blow our air, safety item then we heard a click in A/C and furnace did not ignite. That happened about three times with a failure to ignite. When tech came by in the morning to check on us and see if there were any problems we told him and showed him video from phone and he could hear what it was doing. He asked if we could take phone up to shop so he could check with others and they had never heard of anything like it so they suggested to make sure the communication cable was plugged in tight at the thermostat and at A/C so he came back and did just that. Since that time it has worked great no issues. Of course we only spent four nights in it at the lake then the cold weather decided it needed to show up so no more trips, but we know it has been thru a tornado warning and a 3 inch rain with 60 to 70 mile and hour winds and it worked great.

Mr Bee · 11-13-2019, 12:05 PM

Thanks to all for your reply.
We changed the temperature differential setting from 1° to 2°. Now it seems to be fine. I believe the relay was clicking the system on and off repeatedly because it wasnt sure if it should be on or off.

Thanks

CAG · 11-13-2019, 02:28 PM

That particular "grey box" is the relay for the heat. I am not sure that changing the setting will completely solve the problem but should it need to be replaced the "box" is available on the internet/EBay in the kit form which includes the thermostat. The Dometic part number is 3313191.000.

Your problem is not common but does happen. A faulty relay.

Mr Bee · 11-13-2019, 05:29 PM

I do believe it is still an issue however, we are using the TT now through mid march, so we can keep it on the 2° differential until we can take it in for warranty.
Thanks CAG for that info and numbers, i will look it up on ebay and maybe keep a reserve.

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