[otto]

Good morning. I have a customer with a Carrier 38MAQB09B-301. The indoor unit is a 40MAQB09B-331. We did not install this unit. The serial # is 0118V*****
No cooling call. Power to the indoor and outdoor units. DC voltage fluctuates at outdoor unit from 5VDC up to 20VDC. Does not go into the negative VDC range at all. Difficult to catch on a digital meter but that's what I see on terminals + and S. Carrier is saying that I need a new circuit board on the outdoor unit and I should also get the board for the indoor unit as well.

Quoted the customer for the parts but I have a nagging issue with something. The condensate pump is running continuously. The pump is installed inside the front cover. The cover is very difficult and damn near impossible to remove to get at this pump. Not much in the way of mention of this pump in the service manual. No fault codes and no display on the indoor unit. The outdoor unit is mentioned in the service literature but I see no LED's or anything up there with the top panel and circuit board panel off.

This unit looks like a real pain in the ass to service and I just have so many concerns that I am taking the right path with this. I would appreciate some input form technicians who are familiar with these units and their service. Do I need to look closer at the pump? I don't think it should be running constantly. Is there a way to remove the cover for service access or are you expected to take the unit off the wall? Where is this indoor circuit board? Is it the one mounted to the inside of the front filter cover?

I have access to all the literature but the instructions are a bit vague and worded in a misleading fashion. I can tell it's translated form Chinese.

I realize that I have a few questions in this initial post but I just can't help but think that I'm missing something on this service call. Perhaps the condensate pump seems as if there is no sending unit and was wired constant or there is a sending unit and the float switch has the S wire open but that should give me an E1 fault. The customer said that there was initially an E1 fault but now there is no fault at all and no display or blinky lights on the indoor unit.

 

[CircusEnvy]

Never worked on a Carrier mini split, but they’re all fundamentally the same.

It sounds like you have an internally mounted condensate pump, which is almost always tucked in behind the unit where the line set runs. You’ll have to remove the air handler from the wall bracket to reach it or swing the bottom up with the top still latched in (very difficult to do and doesn’t always work). Having a Mighty Bracket is a huge convenience.

A lot of those crappy condensate pumps have a screen that gums up with algae and it causes the pump to run continuously, if the drain hose isn’t plugged or kinked going outside. Virtually all condensate pumps are wired to shut power off to the air handler or throw a condensate drain error. This will cause both the indoor and outdoor units to stop communicating with one another. I’m not sure how Carrier’s systems handles this, but with Mitsubishi when S1 or S2 is broken, the air handler will be dead and the outdoor unit sits idle.

I would go back with the boards, but first tackle the condensate pump issue because it shouldn’t be running continuously under any circumstance other than improper drainage. Board failures are extremely rare on these systems.

 

[dandyme]

Is the condensate pump breaking the"S" signal? That's not good, should be breaking L2.
View attachment 40MA Service.pdf

 

[otto]

Is the condensate pump breaking the"S" signal? That's not good, should be breaking L2.
View attachment 815385

L2 is 230V so they have the pump break the S line.
http://9459a8a7c04856c345d2-4f83005...45d2-4f8300507cf0a318260a6776e1a92a67.r99.cf1.rackcdn.com/IIK-53DS900-CP-08.pdf

 

[JayMan7]

The pump absolutely should not be running continuously...and yes mini splits are a real PITA to get into. Everytime I break into one I get to hear the bone craking sound of plastic pieces being flexed to within an inch of their life :gah: I'm of course exaggerating, but it is unbelievably annoying to get some of those peices unclipped...it'll make you cringe. They really should use more screws and less plastic clips on those things. Anyway, yes you need to check out the pump first!

 

[otto]

Update: The pump was the problem. I was sent the wrong circuit boards so that was actually good that I did not replace them. Would have been under 5 year warranty anyway.
The pump was installed wrong. Also the overflow was breaking the S line as per the pump IOM. Tech support guy from Carrier said it should break L1, not the S or the L2. I remounted the pump with a new section of hose, above the sending unit as per the IOM but it stil would not pump. Going back tomorrow morning with a new pump kit.

 

[JayMan7]

Update: The pump was the problem. I was sent the wrong circuit boards so that was actually good that I did not replace them. Would have been under 5 year warranty anyway.
The pump was installed wrong. Also the overflow was breaking the S line as per the pump IOM. Tech support guy from Carrier said it should break L1, not the S or the L2. I remounted the pump with a new section of hose, above the sending unit as per the IOM but it stil would not pump. Going back tomorrow morning with a new pump kit.

Nice work! I'm not sure which pump you have in that unit but every one Ive ever seen looked like a total POS

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[otto]

 

[otto]

Pictures
A: I knew I had the wrong board right away. I suspected it was wrong before I got to the job.
B: They said that there are a number of boards available for these units and they need the serial number
C: Unfortunately the installer destroyed the serial number when installing the service switch right over the rating tag. I was lucky just to be able to read the model number. I wonder if the serial number is anywhere else on the unit on the inside.
D: The pump in question. I will be getting a new pump kit, new sending unit and all that jazz.

 

[JayMan7]

C: Unfortunately the installer destroyed the serial number when installing the service switch right over the rating tag. I was lucky just to be able to read the model number. I wonder if the serial number is anywhere else on the unit on the inside.

Freaking installer...man you gotta love them

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[CircusEnvy]

You’d think the mini split manufacturers would by now provide a terminal for condensate pumps so the system would throw an error code instead of acting like an inverter issue. Makes you wonder how many warranty boards have been replaced for this same problem!