Community Forums

Jim_HiTek · 07-07-2021, 09:08 AM

Yesterday, after a couple weeks using the Coleman Mach basement air in over 100ᵒ F temps, something strange happened.

I was sitting in my easy chair watching TV with the ceiling vents blowing cool air on me when this strange smell flooded the area. Thinking it was a fire, jumped up and tried to localize it. It was localized in the area around my chair. Ran back to the bedroom but it wasn't there. Opened the window there and didn't spot any smoke from the area of the basement heat pump.

Ran outside and checked all around the RV for smoke or strange noises. Nothing. Back inside, stuck my nose in the air flow where I could and the smell seemed to be localized to the 4-6 ceiling vents in the living room.

It was 108ᵒ at the time outside, and 85ᵒ inside and I shuddered at the thought of not having any AC, but for safety I shut it off. Some 20 minutes later, turned it back on and it started cooling right away. Still no smoke, and the smell was dissipating.

What the heck? A burst of strong odor that just goes away within 10 minutes? What is that?

The AC has been running since, turning on/off when called for, keeping the RV at the same temps it has been during this heat wave and the smell hasn't come back.

Only thing I can think of is that some electrical component on the basement air's control board smoked but is a component used for the heating section not the AC section.

Been in the electronics/electrical industry for years and it didn't really smell like a component...sort of smelled like a dead animal that you pass in the forest that's been there for weeks so it's not too strong. Have not had a critter issue in this Journey though, and not parked in a mouse area either.

It's a mystery, but I'll go ahead and open the basement air cover and inspect the PCB in there. It's all I got at this point.

Anyone else experience this with their Coleman Mach basement air? Thoughts?

CRV2 · 07-07-2021, 09:14 AM

Usually a burnt or burning electrical board or device has a unique pungent odor and as you said it didn't smell like that. I wonder if the source wasn't something external to your RV, perhaps someone nearby spraying weeds or insects, or working on something that produced the odor and that came into your RV and faded away with time. Hard to know, just thinking out loud. ~CA

Argosy · 07-08-2021, 05:02 AM

I had the same thought, it's fireworks time, maybe someone set some off and you got a whiff of gun powder.

rssnape · 07-08-2021, 05:47 AM

I’m guessing that although unlikely it could have been coolant that escaped. Are the basement air units sealed units? Coolant and compressor oil really stinks.

Jim_HiTek · 07-08-2021, 09:58 AM

Found it! Turned out, it was something in the control portion of the cabinet. Weird because I thought I'd sealed it up well enough that that couldn't happen. The smell shouldn't have leaked into the house side of the unit, but it did. Might be a good thing though. Here's how it's suppose to look under the cover.

The problem was the wiring to those two large relays that are attached to the wall of the cabinet off to the right of the PCB had burnt, melted insulation. One of them the jumper flamed from overheating and carbonized. Broke off, opened the circuit to #2 compressor. There's some smoke damage, maybe some carbonization of the insulation to the other relay but that seems to be it. Resistance measurements of the compressor motor start/run coils seem normal. The #2 relay coil is open circuit, which is a concern that there might be something bad on the PCB but I'll find out late today when I install the new substitute relays.

The #1 compressor is running fine, after I cleaned up the contacts a bit and tightened and reseated all the connectors running current went from 7-8 amps to 15 amps, as shown on the hallway control center display, while running the generator. Wiring to the run/start caps looks good. No signs of overheating. Caps are only two years old.

So I'm going to install a couple 40 amp Bosch type automotive relays in place of the dead relay later today and order the correct relays. Should be cool enough after 8 pm here to get them installed without to much discomfort. I should have the new relays within 3 days.

If it turns out the PCB is bad and won't activate the #2 relay, I'll limp along with only one compressor until it's cool enough to pull it and track down the bad circuitry. Supposed to stay in the mid to high 90's for the next week so really only need one compressor.

Now the worry will be did this stress the system enough that one or both of the compressors might go bad soon? Doh! My fault for not replacing those relays when I was in there in '19.

Thanks for everyone's input!

hattitude · 07-08-2021, 10:09 AM

Good find...

Thanks for posting the info..

**TonyDi** · 07-08-2021, 10:16 AM

Glad you found the problem. Thank you for letting us know the cause. This may help someone else.

Jim_HiTek · 07-09-2021, 10:50 AM

Here's what I used to get me by...these are those typical automotive 40 amp relays but the contacts aren't rated at 277 volts like with the relay I replaced, so it's just a temporary setup to get by until the new direct replacements show up. A box of these relays is only ~$10 as I recall and it's handy to have them in my kitchen junk drawer for occasions like this...

Wired it in temporarily, after trimming back the overheated portions of the wiring as needed. Left the other big relay in place but cleaned up and squeezed the terminals. Added some new terminals and trimmed back the overheated wiring. Found one terminal that had loosened so that's probably where the overheating came from initially.

So that's the end of the story, for now.