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Davelux
04-11-2011, 07:25 AM
I have a 7 year old Amana Hvac system, that just started to cycle on and off out of the blue.

Unit info:
GUVA/GCVA Modle # CF60FCA MFG # P1237210C
Accessory on unit TX410Ao8A
Ztech Controller 2 Zone HVAC W/TE
Totalline Thermostat p374-1100

The unit is a two-stage variable speed heater. The system is set to work at low speed when the air temp is two degrees out of what is called for and high speed when the temp is more that two degrees out of what is called for. It also has a very low speed that runs for a while after the burner/condenser turns off. We only use the one of the zones 98% of the time.

The unit started cycling. The burner kicks on and the fan ramps up to speed but then the fan kicks down into very low speed; the burner stays on. It then attempts to ramp up to speed again maybe achieving low speed for 10 seconds then back to very low speed. The burner never kicks off and no led faults showing.

The amount of time the fan reaches low speed is variable and could be 1 to 40 seconds. Sometimes it cycles like this until it reaches temp. Sometimes it works fine without cycling. Other times it cycles for awhile and then achieves the desired fan speed.

I have tried running the system without the air-filter and checked the system for cleanliness.

My HVAC guy is perplexed and cant find the problem.

Please Help

New symptom

Woke up to the condenser running. No fan inside the house just the outside condenser. The thermostat did not appear to be calling for heat or cool. No red or green light. The thermostat also lost the program settings, they had reset to 0 and the time was wrong. No power outage.

Davelux
04-13-2011, 02:57 AM
New Symptom added to original post

jadnashua
04-13-2011, 11:34 AM
Some thermostats have batteries in them. Does yours? Losing the memory on an electronic device is often (not always) a symptom of a bad battery or a loss in input power. Sometimes, that battery can be an internal rechargable, rather than an easily replaceable, disposable one.

Davelux
04-14-2011, 06:37 AM
Thanks jadnashua

This unit does not have a battery that can be removed. I do not think it it has an internal battery but instead stores the settings on memory. I have pulled the thermostat off the wall, cleaned the contacts....Still no changes.

jadnashua
04-14-2011, 09:05 AM
Older computer motherboards had replaceable batteries, but most of the newer ones use a soldered in ni-cad. This is the least expensive way to retain memory, although there are obviously other chips that don't require a battery. If your thermostat uses one of those, it may have failed. Does the system still cycle when the thermostat is removed? IF so, that would imply an internal or wiring problem of the HVAC unit. If it stops cycling when the thermostat is removed from the circult, it's pointing towards the thermostat. If it continues to cycle with the thermostat removed, then go to the unit itself and disconnect the thermostat wires. If it then stops cycling, you've isolated it to the wiring between them.

tempritespokane
05-05-2011, 07:33 AM
If the unit cycles on and off frequently (also called 'short cycling') it can be an indication of a unit that is over-sized for the cooling work it needs to do.