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StarryHorizons · 29-08-2017, 17:51

Hey Everyone,

I have a Cruisair STQ8C that is behaving strangely. When I turn it on, the fan comes on, air starts blowing and I hear the click I normally associate with the compressor turning on, but the water pump">raw water pump doesn't come on. This (aft) AC unit shares a water pump with another (forward) unit and when turning on the forward AC, the pump comes on. Turning on the forward unit to get the pump on doesn't help as the aft AC still just blows room temp air.

My initial thought was that a trigger had gone bad, but all triggers had proper 120v voltage. Just to be sure, I swapped the wiring around so aft AC was using the for sure working forward trigger and vice-versa. That didn't change anything.

So I took a closer look at the compressor and it doesn't "feel" like it's turning on. I checked all the connections and found no corrosion or anything, and all terminals are reading 120v. The remote display hasn't thrown off any error codes or anything that might be helpful.

AC is not my specialty and of course this would happen right before the in-laws visit in Fiji, where of course there is no Cruisair service. Does anyone have any more suggestions that I might be able to try?

Thanks!

David

TheOffice · 29-08-2017, 18:54

Check for a clogged water line. If you pull the hose off the seacock you should be able to blow through the line. You may have to suck on the hose to clear it.

StarryHorizons · 30-08-2017, 03:26

Quote:

Originally Posted by TheOffice

Check for a clogged water line. If you pull the hose off the seacock you should be able to blow through the line. You may have to suck on the hose to clear it.

I thought of that, but I can't see how that would explain why the pump would fail to turn on when the aft AC is turned on but the pump (it's shared between the two AC units) will run properly when the forward AC unit is on.

If the water line for the aft AC unit is clogged, I would think that the pump would still turn on but that I wouldn't get any water flow. The pump just doesn't turn on at all.

edmundsteele · 30-08-2017, 04:33

Had a similar problem with a Cruisair unit. I cut the female plug from a household extension cord and wired the cord into the supply pump, bypassing the Cruisair control board. Plugged the cord into a 110V outlet and the pump ran. Turned on the A/C unit and it ran and cooled, proving that it was a control board problem. If you can find someone who will swap out the “relay” chip in the control board, that might be the way to go, otherwise buy another control board – it may be cheaper than a board repair.
Ed

**Symphony** · 30-08-2017, 10:12

Quote:

Originally Posted by edmundsteele

Had a similar problem with a Cruisair unit. I cut the female plug from a household extension cord and wired the cord into the supply pump, bypassing the Cruisair control board. Plugged the cord into a 110V outlet and the pump ran. Turned on the A/C unit and it ran and cooled, proving that it was a control board problem. If you can find someone who will swap out the “relay” chip in the control board, that might be the way to go, otherwise buy another control board – it may be cheaper than a board repair.
Ed

good advice here - you might also use a magnifying glass to look at the control board and the wall unit/ thermo circuit board. I found one of the traces had lifted and parted leading to a very similar situation to the current problem. it was an easy soldering fix.

I also researched replacing the entire board too, the prices were reasonable, but might take a while to ship to FIJI. Paradise does have its downside

Outlaw7 · 30-08-2017, 10:30

In all likelihood you have a pump relay control box that the individual units talk to. The unit send a 24 volt signal to the relay box which in turn pulls in the relay in the box. You will end up purchasing an expensive control board for a $28.00 part. For cruising boats the pc board controlled units are a bad choice.

Squanderbucks · 30-08-2017, 13:47

You have already proven that the pump itself is ok. Possibly the compressor is locked due to a faulty High Pressure Switch. Mine was and even though pump was fine it would not turn on because the High Pressure Switch would prevent it. switch was Approx $40 item and switching it out was easy.
How I was told by Dometic tech support that the way to check it out was use a small jumper wire across the High Pressure Switch wiring terminals(remove the two push on blade type connectors and connect tem together) I use small wire with two alligator clips - and turn the unit on. If it runs when jumped then the switch is bad and then you know to replace it. If still no go then you have to look elsewhere. Went all through this just 3 weeks ago. In my case pump failed and restart attempts blew out the HP Switch.
Replaced Pump but without doing the jumper test I was still stuck. works fine now.

Jim473 · 30-08-2017, 18:22

I have a similar Cruiseaire system. Both units share a common cooling water pump. The units and the cooling pump all connect to a separate remotely located control box. This control box is powered by ONE of the two electrical circuits. (I have two 15A circuits - one each unit) That circuit MUST be on, even if it is for the unit you are not using ( you can turn it off at the stat).
When either unit calls it causes the raw water pump to start, then the compressor. If compressor starts without cooling water will get HP error, indicating compressor shut down. Not sure, sounds like yours is not starting-should start even without cooling water then throw an error. Unless a flow switch has been added.
Electrical schematic is in the pump control box.
Good Luck
Jim

StarryHorizons · 31-08-2017, 03:16

Many thanks for the replies everyone. I did the jumper wire test on the High Pressure Switch, but no dice.

At this point I think we're narrowing in on either the control board or the compressor. Does anyone have a suggestion on how I might be able to determine if it's one or the other? Hopefully it's not both!

And because when it rains it pours, my multimeter has decided it needed an early retirement as well. Not a whole lot of shops around the Lau group of Fiji and we'll need to go hunting to find another boat to borrow one. Fiji may be paradise, but it's not without it's challenges!

Edit: Just had another thought... The fan is turning on even if the compressor isn't. Would that indicate the control board may be working if it's passing power along to the fan?

steve77 · 31-08-2017, 04:48

We had a similar problem when in Gibraltar. In my case, I tapped on the relay a couple of times and was able to get it to actuate. This meant I could get the unit to run, and I would do this each afternoon so the boat would cool down for the evening. Luckily our daughter was coming to visit and brought a new control board from the US, so I didn't need to do this for very long.

If this works for you, perhaps a knowledgeable shop can replace just the relay for much less than the cost of a new board.

Best of luck!

Steve

84SeaRay · 31-08-2017, 05:24

Quote:

Originally Posted by TheOffice

Check for a clogged water line. If you pull the hose off the seacock you should be able to blow through the line. You may have to suck on the hose to clear it.

Just had same problem. Did acid flush with barnacle buster worked great.

landsend · 31-08-2017, 06:32

Agree with searay. If you use your Ac alot an acid flush is part of routine maintenance. My ac would turn on, shut off but pump would still stay on. Wasnt getting enough water flow through system.

StarryHorizons · 03-09-2017, 03:17

Since I know everyone was waiting on the edge of their seats wondering about the resolution, I figured I'd better come back and post another update.

I swapped out the control panel with one that I know is working. No change.

Then swapped out the compressor relay with one I know is working. No change.

So I'm forced to conclude that the compressor has gone bad. Which is consistent with the fact that it doesn't "feel" like it's running when the unit is one. Unfortunately, the nearest Cruisair dealer is in Australia so in order to keep the in-laws happy I shall now be swapping out the bad unit with one of the other 5 units on our boat. Gotta love manufacturer overkill!

Thanks everyone for the help!

**Symphony** · 03-09-2017, 22:41

rather than move a working compressor (which might not work after being moved around) is there a way you could use venting, or flexible vent hose, to bring the cold air from the closest AC unit to the in-law's cabin?

LoudMusic · 08-09-2018, 20:12

Quote:

Originally Posted by StarryHorizons

Since I know everyone was waiting on the edge of their seats wondering about the resolution, I figured I'd better come back and post another update.

I swapped out the control panel with one that I know is working. No change.

Then swapped out the compressor relay with one I know is working. No change.

So I'm forced to conclude that the compressor has gone bad. Which is consistent with the fact that it doesn't "feel" like it's running when the unit is one. Unfortunately, the nearest Cruisair dealer is in Australia so in order to keep the in-laws happy I shall now be swapping out the bad unit with one of the other 5 units on our boat. Gotta love manufacturer overkill!

Thanks everyone for the help!

Did you ever come up with a solution for this problem?