Please Tell Me It Isn't the Compressor

[Tankergirl]

Hi all, I'm new here and on my first day I'm hoping for some good news. I have a '99 Carrier Ultra Fresh. 2 months ago it had a ***** leak fixed. When we went to pick it up it wasn't running properly. It was shutting down for High CDT. The mechanic rebuilt the top head in the parking lot (he put new reed valves in). Still shut down for High CDT. He determined the new dryer had been put on backwards. He put a new one on in the right direction and it ran fine. 2 days ago it starting shutting down for high CDT. It is getting hot, using a infrared temp gun we know this to be true. We took it to the Carrier dealer in California and it acted fine in the shop. They believe the culprit was a dirty radiator/condenser. The next day it shuts down for High CDT while on continuous but runs and cools fine on cycle, with the exception that every 8-10 hrs it will fail to start. Turning the switch off then on it'll run good again. Today it's shutting down for High CDT on both continuous and cycle. We called the closest Carrier and the mechanic automatically said we need a new compressor. He can't get one tonight anyway so we'll continue on down the road to make our delivery and go to a shop tomorrow.
I'm hoping someone on here can give me hope that there could be another issue other then the $5k compressor. Has anyone ever had this issue and it nor be the compressor?

[Magoo]

Hi Tanker Girl.
Can only suggest system is contaminated with non condensibles, ie air. After all the work done on system. Requires system refrigerant to be recovered and evacuated and re-charged with fresh refrigerant. That is after establishing that the system is leak free, so as not to repeat the problem.

[Tankergirl]

Oops.. I guess I left that part out, sorry. It was evacuated and refilled with fresh oil and ***** and ran fine up til Friday.
I appreciate the reply.

[abbsnowman]

A couple of things come to mind here, you said they put reeds in one head? What about the rest? Are the unloaders functioning correctly? Have you cleaned the condenser? There could be quite a few reasons but I doubt it is the compressor, or at least not enough to replace. I would be looking at above first.

[Tankergirl]

A couple of things come to mind here, you said they put reeds in one head? What about the rest? Are the unloaders functioning correctly? Have you cleaned the condenser? There could be quite a few reasons but I doubt it is the compressor, or at least not enough to replace. I would be looking at above first.

You are my new favorite person, I promise not to hold your feet to the fire but I'm so glad to hear someone say that...

Yes, to the cleaning. They did that in Cali on Friday. So since it's clean could the fact that there are a lot of fins that are smashed be an issue? I'm not sure I would be convinced as they have been like that for a long time and we never had an issue.
They only replaced the reeds in the top head. That is the one that is getting hot (330+*) according to the temp gun.
Give me a definition on "unloaders"? I think you're referring to the valves that control the flow of *****? How can we check that they are working properly?
We are at a truck stop fuel island using a water hose to keep it cool and it seems to be working thus far.

[Boss302]

It could have possibly blown the head gasket under the center head. The unloaders are the valves on the outside heads that load and unload the outside cylinders. If the compressor is fully loaded, running on 6cyl. and the only head that is hot is the center one, you need to pull that head. More than likely a blown head gasket or broken discharge reed. If it is the discharge reed, you need to have them check the piston for slop in the wrist pin on the cylinder that had the broken reed. The wrist pin doens't get oiled correctly due to there always being pressure on top of the piston and wears the wrist pin bore out pretty quick.

[tbirdtbird]

And get a fin comb and straighten out the fins. Doesn't matter if it 'ran OK before'. It will run better and cooler with the better airflow from straight fins.

[abbsnowman]

I would get that condenser fixed as well.
The unloaders are on the front and rear heads. They allow the compressor to run on less cyclenders when required. If all heads are "loaded" they should all be around the same temp. (Top head will always be hottest.)
Thing here is though, there could be any number of reasons for this issue. I think you have answered at least a bit of your own question by saying that cool water on condenser helps. Thats probably what took out those reeds in the first place. Did they get all the pieces of reed out?
So many questions!
Smartest thing to do is get it to a good shop and have them look at it properly.

[lowcool]

it does seem a bit nasty to replace the compressor due to over temp related problems.

if its as boss 302 states i would be looking for another compressor manufacturer and hopefully it might not be to hard to adapt it.

good luck with it.

[Boss302]

it does seem a bit nasty to replace the compressor due to over temp related problems.

if its as boss 302 states i would be looking for another compressor manufacturer and hopefully it might not be to hard to adapt it.

good luck with it.

Maybe I was misunderstood. There isn't a problem with the compressor oiling. It is when it is ran with a broken discharge reed that causes the problems.

[gravy258]

How hot is the ambient temperature when the fridge is shutting down?

Check a few easy things:
Is the fan cowl still fitted(plastic or alloy wrapped around fan). This will affect the air flow across the coil.

Does it happen when your motoring along, or when you slow down/stop?
Could be the truck is blowing heat into the fridge at slow speeds/standstill

As the previos poster stated, take off the front panel, straighten all the fins on the condenser. Then with the fridge running in high speed blow out the coil with compressed air. Then get some coil cleaning acid, apply as per instructions. Then pressure wash slowly from top to bottom with fridge running in high speed.

If this doesn't help, you need to take it a repair shop, one that has a clue.
Diagnosing the compressor over the phone is rubbish.

[BRM]

it could be something as silly as the wrong valve cover gasket was used . As far as i know there are 2 diff. gaskets , the ones on the sides do not suit the top head

[Vandman]

Possible front unloader - on the front head of the compressor (closest to you) there is a stem with a magnet coil on top.

Turn unit on, let it run for a few minutes. on your micro under "unit data" check what your suction pressure is.

is it under or over 25ish psi?

Take a wrench and hold it to the top of the unloader i had mentioned above. does it stick like a magnet?

it SHOULD stick if your micro says suction PSI is over 25ish, it SHOULD NOT stick if its under 25ish psi.

you could also have a bad suction transducer.

[Magoo]

Tankergirl.
Your earlier comment that the condenser fins are smashed would be the real problem. Now compressor is doing the duty it has to get rid of the heat through the condenser fins, if the air is blocked then you have the current problem and need for water. At 300 + degrees something will fail soon, oil then refrigerant then compressor.

[perthtech]

check rear head gaskets, these are the first to fail, if the unit been doing alot of chiller work.
Also make sure the head gaskets are the correct ones, i have seen people put O5G twin port gaskets on the old style O5g compressor.
Do a effeciency test on the compressor, this will tell you straight away if your gaskets are blown.

[DaButcher]

Hmmm, all this talk and no one mentioned quench valve or the fact that most ReeferTek's have learned to rebuild all three heads not just one.

[NoNickName]

It looks like the high pressure safety bypass valve is stuck open and blows back into the suction. The resulting high suction superheat causes high discharge temperature.

[DaButcher]

It looks like the high pressure safety bypass valve is stuck open and blows back into the suction. The resulting high suction superheat causes high discharge temperature.

Don't believe a Carrier Ultra has a high pressure safety bypass valve. It does have a safety plug on the receiver tank that blows outside the unit with extreme pressure or heat.

[perthtech]

Agree, but the OP mentioned only the centre head was redone.

[D.D.KORANNE]

sounds like high pressure high temp gas is being compressed again i.e. somehow high pr gas is leaking back to suction side raising the discharge gas temp . If you have a start unloader on the comp , it is not shutting down completely & part remains open .

[Boss302]

Somebody needs to run the unit fully loaded and take the compressor head temps, and as stated above, if it is a R22 unit, make sure the quench valve is functional.

[tspgr]

1. check that the high cdt is correct by test the temp of the heads
2. check the suction pressure when its working
3. check all the and I mean ALL the head gaskets and valve plates
4. check what gas have they put inside
5. check the small by pass valve that gives pure liquid to the suction
6. if you solve the problem give us a feedback as thanks for all the techs that answers to your reply ....

Mixalis patra greece

[mattym]

this will sound like a silly answer but has the engineer tried a new Compressor Discharge Thermistor (CDT)

[kool@er]

with all the suggestion above, (btw, all good suggestion), nobody has yet mention to check the rotation of the condenser fan blade and to see if they are set in the opposite position that they should be in.