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Trane Heat Pump Not Cooling

5 posts in this topic

I came home today to discover that the Trane Heat Pump that cools the main part of our house is not cooling. Thankfully, the bedrooms are on another unit!

The unit was installed in 1990, but the compressor was replaced in 1995.

The filter was moderately dirty, but less than six weeks old (we do have hardwood floors which causes it to get dirty quicker.) I replaced the filter.

The evap coil IS NOT frozen.

I have cleaned the evap coil within the year.

In the past when the filter was a bit dirty the evap coils would freeze up.

The evap coils seem to freeze up more often as time goes by.

The compressor fan runs.

At first the compressor was not on, but after the unit was off for an hour IT CAME BACK ON when re-powered.

There is no condensatiobn on the return (?) line (the insulated one)

The supply line does not get warm (small line without insulation.)

The air blowing out from the condensor unit is not hot

When the compressor ran for a short while the other line (bigger and insulated) felt a bit warm. It should be the oposite in the coolng mode corrct?

The compressor sounds normal.

After opening the outside unit and cleaning the coils the compressor came on when the unit was re-energized, but the fan cycles off and on. The fan runs for :30 seconds, shuts off for five seconds, then re-starts and runs another :30 seconds. the compressor stays on.

I didn't run it more than a few minutes like this.

Low refridgerant level?

If the compressor runs isn't it "OK"?

I have the disconnect "off" right now.

The unit was cooling fine as of this morning.

This sounds stupid, but my electric usage seems to be higher.

Is the unit working harder due to a low freon level?

Any ideas?

Danny Brown

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The compresor is running but the fan is cycling on and off? Does the fan motor have power going to it when it cycles off? It sounds like the fan motor is no good, check the cap first. Wouldn't hurt to get a set of gauges on this once the fan problem is fixed.

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The compressor fan works fine now that everything is dry outside.

HVAC repairman came by:

There seems to be a restriction in the (low pressure?) line.

The side that should read 70 (psi?) is low (40-ish?)

He didn't have a .60 orifice and would need his evacuation system as well.

He is coming back late Monday or early Tuesday.

It appears that the compressor is working, but he said that it could be a part from it that has caused the restriction. In other words... the compressor could be failing. YIKES!

He said that the coils could be coming apart? Somthing about a plastic somthing or other inside the compressor that can touch something and cause it to go to GND? If it goes to GND it burns up the coolant as I understand it?

The compressor's automatic shut-off is turning the compressor off after a while due to the pressure imbalance.

To add to the fun, when he was un-hooking his gauges the Schrader valve stuck open!

He had to put the cap on to stop it.

That'll be one more thing to replace!


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Oh yeah hes got you set up good. Next step is to sell you a compressor or a entire new system, watch your back sides and front there son. What was the high pressure side reading when he got the 40ish reading on the low side? If the readings on the high side was also lower than normal it may just be low on refrigerant! The orfice tube he is referring to is in the liquid line high side of the system between the condensor and the evaporator so not sure what he means by a restriction in the low side of the system. On a properly installed system there will be a filter drier brazed into the line before the orfice tube it is rare that anything would get past this filter and stop up the orfice. It does happen but only rarely. If I were you I might have someone else give me a second opinion before I allow this guy to rip the system apart. Just my opinion at least call him back and ask him some more questions tell him your AC advisors have requested additional info to confirm his diagnosis. 1.  We will need the outside ambient air temp at the time the psig guage readings were taken  2. Low side pressure psig  3. High side pressure psig  4. Confirmation that evaporator coil is clear of icing 5. Confirmation that blower is operating and moving sufficent air across the evaporator 6. Confirmation that the condensor fan is operating normally  7.  Line temp reading  4 in in front of the orfice tube and  4 in past the orfice tube 8. Line temp reading on return line right at the condensing unit  As soon as you can post all this information your AC tech can be checked out for correct diagnosis. NOTE: most of the time if a technician actually does check all the above items the correct diagnosis will be so obvious that it cannot be ignored the problems start when a proper check is not done and a quess is made as to what the problem is kinda like a dog chasing its tail just a plain waste of time and energy.

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:dude: Thought I'd chime in. Your A/C guy is standing in a field, hearing the hoofbeats, but looking for zebras.

I'd need to know more about the system,  but A restriction will cause a low suction pressure, a high high side pressure and may show frosting at the restiction site. My gut feeling is a control problem (IE: a pressure switch, defrost control or the like.)

The fan cycling almost seems like it was trying to force a defrost.

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