fan cut out on heat

[mangostack]

i have a carrier ac running with r22,
when on cooling suction is 58psi and machine runs perfectly well all day,
when on heating the machine runs correctly for approx 10 mins then... fan cuts out, discharge pressure drops from 270 to approx 240 psi and suction drops to approx 35 psi. Obviously the exterior heat exchanger starts to freeze
i have evacuated system and recharged and i am thinking that my next step would be to link the fan in to run full time in order for external coil to work better.
Am i missing something obvious?
is it correct to try linking fan as next step?
thanks for your assistance in advance :)

[Gary]

fan cuts out

Outdoor fan or indoor fan?

[Brian_UK]

Does the fan restart after a period ?

Should the fan stop as part of the control strategy?

[paul_h]

Most a/cs have controls that cycle the outdoor fan to stop the indoor coil getting to hot and discharge pressure getting too high.
If it comes back on, everything is normal. If it cuts out excessively, check pipe work, thermistors, indoor airflow or it may be overcharged (ie precharged to a certain pipe length but installed with a really short run).

If it doesn't come back on after it first turns off, you have a control problem or even fan motor problem.

If you wired the outdoor fan to run all the time, your discharge pressure and indoor coil temp would be too high.

[nike123]

Check your air filters in indoor unit! Check indoor coil thermistor for proper values against temperature.
Control logic should not cut-out outdoor fan when pressure is 270 PSI. That is too low pressure/temperature for cut-out. It should be at around 350 PSI (145°F)

[nike123]

is it correct to try linking fan as next step?
:)

No, its not! You need to find cause of problem instead of treating symptom.

[brunstar]

yeah it sounds like it is not dissipating the heat from the indoor coil, like stated with other responses, indoor coil thermister reading too high, indoor fan motor down on air flow or blocked filters.
What all the other boys have stated..

[mangostack]

Cheers guys twas the ineterior sensor on pipe, replaced with one that gave a normal reading and all was good

[Brian_UK]

Good, thanks for the update.