Cruisair do-it yourself repairs

[fixin-to-cruise]

I am looking for the model number for the compressor on the Cruisair A/C units on my boat. They are 1990 vintage Cruisair Model FS7C-P (230 VAC with SMX controls). The FS7C-P is on the electrical box label next to the compressor. I have 2 of these units with compressors that were replaced in Spain by the original owner with 50Hz compressors. Cruisair seems to always use 50/60 Hz compressors. One fried itself in April and has to be replaced, but I hope someone can get the number off their original compressor and post it!!!!

The “compressor model number” is on a metal plate on top of the compressor. It’s the 1/8” tall number on the right side under the 5/16” tall “bill of material number” along the top of the plate. I suspect it might be AK5483E but would like confirmation before buying 2 of these.

After having a “professional” A/C service try to fix another unit 3 times for $900 (unsuccessfully)…I bought a vacuum pump for $220, acetylene “TurboTorch TDLX2003” for $230, mini-acetylene tank for $90 and R-22 bottle for $80. I already had the gauges and A/C valve wrench. It turned out that there was a bad reversing valve that cost about $150. It is silver soldered in the A/C plumbing and the unit now works great.

Air Conditioning work is no big deal after you figure out how to do it, and there’s a lot of information on line. The price of the equipment is about the price of a service call for a compressor replacement.

For your first attempt at A/C service you need only a gauge set and the special square drive ratchet wrench for the charging valves (don’t go without safety goggles!). The gauges are red (high pressure) and blue (low pressure) and have a red and blue hose to connect to the compressor and a yellow hose for charging. Any A/C supply place will sell them to you. Cost is probably about $40. Close the gauge valves (closes to the charging hose) and with the hoses attached to your running A/C unit you can crack open the valves (they turn backwards!) on your A/C unit and read the pressures. Basically the pressures should be 250 on the high side and 60 on the low side. The A/C should shut down if the pressure on the low side is under 30 psi for more than a couple minutes, usually an indication that you need more Freon, the most common problem. A Cruisair corporate tech rep said pressures above 270 are "getting high" and indicate a possible lack of cooling from scale and recommended "calgon" for descaling.

 

[krush]

Basically the pressures should be 250 on the high side and 60 on the low side. The A/C should shut down if the pressure on the low side is under 30 psi for more than a couple minutes, usually an indication that you need more Freon, the most common problem. A Cruisair corporate tech rep said pressures above 270 are "getting high" and indicate a possible lack of cooling from scale and recommended "calgon" for descaling.

Doing this stuff yourself is possible, but unless you understand how to PROPERLY use the tools you most likely are not going to get full capacity out of your unit and destroy it at worse.

I can tell you right now that your "should be 250 on the high and 60 on the low" is not going to cut it. The pressure varies greatly with the coil temp, which varies greatly with the load being placed on it. I'm a mechanical engineer and I could go into all the theory (and make it understandable) but that isn't necessary for repairs (though it helps to understand the "magic" system). Depending on the design of the unit (fixed orfice/cap tube or Thermal expansion valve) the way to determine the right amount of refridgerent is to check superheat or subcooling. You can also often get away with a sight glass if using r22.

The brazing and sucking down parts aren't too difficult and easy to learn, but reading and interpreting those gauges and temps isn't intuititve to most.

I can dig up some simple articles and dicuss this topic if you want. I've been working on HVAC stuff for a few years and learned much from my friend who does this stuff everday. To put it shortly, charging isn't too hard to do correctly, but being able to figure out where the problem is in the system by looking at gauges takes a little more thought. Your method will only yield good results under certain water/interior temperatures.

 

[SKYCHENEY]

I don't know. I once had a unit that needed a little R-22 every season. I just hooked it up and added it until it was cool again. That always seemed to work and I had no idea what the pressures were. I did that for 10years until we sold the boat and never put any other parts into the whole system.

 

[Boatsb]

Kind of like the old engine adjustments. There was a time when I could set the points with a dwell meter and tune the rest by ear. carb, Timing ect. I also maintaines a refrigerated food plant that had 10 compressors and the "feel" of the pipes fpr hot and cold along with general pressures worked great. Some of the units were 20 years old.

If I remember the calculations are based on ambient temperature, Relative humidity and pressures and temps of the high and low sides all of which are related. Any one will effect the others but I vote for 90% efficiency and cooling over waiting for the $900 service man and sweating.

Just one last note. I had a service done on my home unit. It's 10 years old and I had the contactor replaced as it showed burning and had him top off the unit with freon. That and an inspection cost about $300.00. 2 hours later the system was shutting down. The fan on the compressor was bad. He was nice enough to replace that too. Only another $275.00 including the service call. The moral of the story. Get spare parts while it works or prepare to be a victim.

 

[krush]

Quoting campbelde from this thread: http://www.samsmarine.com/forums/showthread.php?t=6756

As a HVAC technician, you can do it yourself. Not sure, but maybe there are some classes at a local technical school that could teach you what you need to know. It's very important to charge units properly. Over charging is as bad as under charging. Dirty coils and heat exchangers can give false readings when checking a charge.

Again, it's not rocket science but prior knowledge is a must. Keep in mid that you are dealing with high pressures that could be dangerous if not properly handled.


With all the work that many of us do on our boats, I feel that this is above the normal level of expertise, but not out of the realm of the do it your selfer.

I'm not saying you need to be EXACT on charge. With TXV systems, you can be off from the "optimum" charge and loose little capacity. I'm just saying putting 60psi on the low side at all times will not work.

Trust me, I used to think like ya'll...throw some refrigerent in and let's go...it can't hurt to have too much. Well, over the years I did this and guess what...one day a system worked great, the next day it was warmer and PSSSSSSSSSSSSHHHHHH the high side shot to over 400psi and blew the internal pressure relief in the compressor. The day before my pressures looked "ok". I didn't know what temp/pressure tables were back then, but be sure I learned after that episode.

I've been browsing the forums and notice the abundance of A/C problems. It doesn't makes sense to me. How many of ya'll have these problems with your A/C units in your homes...what about your refridgerators?

Granted, I think cruisair ain't made to the best standards, but they should not be failing so much. They should not leak over time unless there are rubber hoses in the systems. Compressor should last indefinitely...the rest of the system should corrode away before the compressor craps out.

I realize the marine environment is brutal, but the compressor is hermetically sealed from it. It's not hard to keep the system in tip top shape as a DIY'er. It's also not hard to repair it, but you need to learn how it works and repair it correctly!

High head pressure, normal suction...clean the condenser coils. Low suction but normal head and temps check out...dirty evap. How to know if you got the right amount of refrigerant in...sight glass or check the subcooling. It's the relationship of the pressures to coil temp that tell you the charge, not just pressure (and pressure is dependent on the air temp over the evap and water temp over the condenser) .

This stuff is not rocket science and I really think everybody here can grasp it and save themselves lots of money! It's been my experience that often HVAC techs often do not fully understand the fundamentals (I know tons of engineers that don't, but I'm allowed to trash talk them, cuz I am one hahah)

 

[Banshee36]

As far as the scales on the gauges, the green dial insde the low gauge, blue in color is the temperature of the evaporator coil. I usually charged my units till it was reading about 45-50 degrees. Always works. But charge the units slowly , after you add the gas, let the unit run for 10 minutes or so then add more gas if necessary.
JW

 

[Boatsb]

and add GAS. The old units you could add liquid. The sealed units will not take liquid well and may fail.