Carver Owners Forum

Background- New to me 1998 405 Aft Cabin, 7.4 Horizon engines. The previous owner replaced both forward and Salon HVAC units this year before my purchase. Installed Webasto units.

I noticed on night 2 of our trip bringing the boat home, the salon A/C unit (which also cools the master stateroom) stopped working during the night and had an E01 code. I did a quick Google search and found that it’s “Compressor High Pressure” fault. Likely fix recommendation was clean filter/condenser. I wrote that off as, add to the list.

Last night I turned the heat on and both units ran fine for awhile. Noticed master stateroom was cooler than salon. Well, the salon unit stopped and had the E01 code again. I let it stay off for 30 or so minutes, then started again. It ran for about 10-15 min then E01 code again. I checked water flow and same amount of water was coming out both port and starboard sides at the bow. I remembered our first night on the boat I only ran the salon A/C and had zero issues. So last night after it failed the second time I turned the forward system OFf. Then after 30 or so minutes I turned the Salon hvac unit on and it ran for about an hour without problem. This leads me to believe it’s NOT a clogged filter or coil, but a water flow issue.

I’ll check strainer again, but as I said the exit water flow looks good, but I have nothing to compare it to since this is my first boat with this system.

I searched this forum and found one string with same issue, but the result or fix was not posted.

Any recommendations??

Thanks!!

Once you're checked and verified that the screen basket is clean and that the pump impeller is clean (I've seen several cases where the impeller has collected some 'junk' and becomes less efficient), then the next thing for that problem is usually is to de-scale the condenser. Even though the flow is "good", is it "good enough"?? I'm guessing the salon unit is a 16k BTU. If so, it needs a lot more flow than the smaller ones which might be forward or aft

You can actually measure the flow by putting a bucket underneath the output and counting how long it takes to fill, and extrapolating to get GPH. Then you can measure the temperature of the outflowing water and compare to the "lake" temperature to see what the actual rise is.

As a side note. And this is my opinion.
I know you haven't had your 405 too long. But I belive you will find that not having a hvac unit for the aft cabin will be aggravating especially in the summer. You'll notice that the ac panel is setup for 3 ac units. Putting 2 in and trying to cool the salon and aft cabin is rather sorry theres just not enough air flow.. My 405 was also sold that way. You might think it will work and depending on your useage it may. You will find as you sleep that the cabin will definitely heat up quite a bit more than youd think. It wasn't long before i installed ac #3. Shutting the cabin door I can also lower the aft temp to sleep cooler rather than trying to cool the whole boat more.

I had the same issue with my Dometic, but just the AC function. These units require a lot of air flow, so I took everything out of the storage area near the unit. During hot weather, I run a small fan into that storage space to force more air in. After increasing that air space, unit runs fine. Seeing as you had the same issue with heater, I would guess it is water flow related. That error code is almost a generic code, so it doesn't help much to diagnose the issue. er

Just a quick note, if you get the high-pressure error in the cooling mode, it's on the water side. If it happens in the heating mode, it's on the air side.

Mikwallace wrote:Source of the post ....I remembered our first night on the boat I only ran the salon A/C and had zero issues. So last night after it failed the second time I turned the forward system OFf. Then after 30 or so minutes I turned the Salon hvac unit on and it ran for about an hour without problem. This leads me to believe it’s NOT a clogged filter or coil, but a water flow issue.....

Whether one or more units is running shouldn't make a difference as water will flow through all of them at all times regardless of whether you're running one or both units.

Check your air flow as others have mentioned, and the fins on the evaporator to ensure they're clean. Here's a thought though, is the raw water pump the original, or did the previous owner replace it when he upgraded to new units? Either way, does the output of the current pump meet the requirements of the two new units you now have?

Follow up:

The strainer wasn’t too dirty, but I cleaned at anyway. Not sure if it means anything but the strainer handle was inline with the input and output opening in the strainer. I replaced it so the strainer handle didn’t obstruct the input/output ports. Pic below:

After:


Before:


I cleaned both the return air filter and the filter mounted on the HVAC unit itself. None of the filters were dirty. I did find the return air temp sensor had fallen off the return air opening and lying in the bottom of the cabinet where zero air was passing across it. I mounted it where return air would pass across it. So far, so good. Works without error, fingers crossed.

On another note: when I saw the return air temp sensor was ineffective on the aft unit, I thought I’d check the front HVAC unit. I didn’t pay much attention in hot weather, but noticed the other day when the front heat was running it never cutoff or satisfied the thermostat, it just kept heating. The inside temp was about 56*, so I set the thermostat to 65*, but it never cutoff and finally I manually turned it off when inside temp was 75*! So I checked the forward temp sensor and it was lying down in the bilge. So I attached it where it would sense the return air, now it cycles as it’s suppose to.

Both units are new and were installed in June 2022.

Follow up:

The salon HVAC is struggling for air. The installation manual recommends a minimum of 140 sq in return air. It only has about 110 sq in return, plus the couch is only about 3 inches from the return air register. So I’ve got to increase the return volume and also put a filter on it.

The boat always had a musty odor. I’ve added air fresheners but it only covers the odor. While digging into the fwd HVAC, I found where the return air was basically from the bilge! There was a return air register that provided 63 sq in; however, the installation manual requires a minimum of 104 sq in. It was really a mute point because the fwd HVAC was sucking air from the bilge. So I built a return air plenum on the return side of the system and installed a 140 sq in register with filter. And now I don’t notice that odor after returning to the boat after a few days. So I do believe the front HVAC is fixed! I’ve read other threads where apparently that was SOP for fwd HVAC systems allowing return air from beneath the fwd bunk? Sounds dangerous to me!

Maybe this will assist others.

It was really a mute point because the fwd HVAC was sucking air from the bilge.

I can see this would be an issue as you would draw heated unconditioned warm air as opposed to cooler conditioned air when drawing from the cabin not to mention the bilge odours introduced to the cabin. glad you got this issue fixed the right way, not sure what Carver was thinking when they set that up then again it's a boat and many things do not make much sense.

I’m learning more about these HVAC systems as time goes on. I have a follow-on question. Both HVACs have heated just fine this winter. I only run them when I’m on the boat. My aft HVAC is a 12K unit and operates as a home unit does in respect to satisfying the thermostat then the compressor turns off and the fan runs long enough to cool the air handler down, then the fan turns off. Once the inside temp drops enough on the thermostat, the heating cycle starts again. The front HVAC is a 10kw unit. Both units were replaced last year. The front unit operates as the aft unit does, EXCEPT, the air handler fan never turns OFF? Once the thermostat is satisfied the compressor turns off but the air handler continues to run. The fan mode on the thermostat is set to AUTO. Shouldn’t the air handler fan turn OFF once the thermostat is satisfied?

Correction:The Salon/Aft hvac is 16k BTU and fwd hvac is 12k BTU.