Air Conditioner Condenser Fan Replacement

The Problem

Once the weather stated to heat up again my grandparents informed me that their air conditioner had stopped working. After going around to their house and turning on the air conditioning it appeared (from the inside at least) to be working perfectly. The interior fan started working and cold air started to be pumped out of all the vents in the house. After about 30 seconds however the air being pumped out of the vents went back to room temperature. It seemed that the thermostat had switched off the condenser unit.

After navigating the obstacles and getting in a position where i could inspect the condenser unit it became apparent that the fan on the top of the unit was not working. The compressor however could be herd running for short 30 second intervals (after which the compressor was automatically turned off due to high head pressure.)

Possible Causes

My first thoughts were that the fan may have seised up as a result of being exposed to the weather for over 30 years. I removed the cover off the fan and tried rotating it. To my surprise it rotated freely. Evidently that was not the problem.

If the motor spun freely my next thought was that the motor itself was no longer functional. Firstly I tried testing the fan run capacitor, however it appeared to be ok. My next step was to test the motor itself.  To test the motor I removed it from the condenser unit (which turned out to be quite a task) and tested its resistance with a multimeter. The resistance turned out to be incredibly high so high that no current would have been able to flow through the motor. This was therefore the problem and the only thing that could fix the problem was a complete new fan motor. This however still left me with a problem. The old fan assembly was essentially rusted to the old motor and the bracket that held the motor in was somewhat destroyed in the process of removing the motor. What I needed to find was a completely new fan motor and fan assembly.

The Solution

After some looking around on the internet I came across a type of fan commonly fitted to HVAC systems which had everything I needed. It had a new motor and new fan blades. What made it better was that it could be bolted to the top of condenser unit meaning I would not have to try and reconstruct the bracket that held the old motor in place. After measuring the size I ordered one of these fans.

Replacement Fan

 Installation

The installation was fairly strait forward especially since the old fan had already been removed.

The first step was to take the top off the unit and select an appropriate location for the power cord from the new fan to enter the condenser unit. After finding an appropriate location I drilled a hole and pushed the cord through.

New fan cable being routed into condenser unit.
New fan cable being routed into condenser unit.

The next step was to connect the fan to the appropriate power source in the condenser unit. Luckily there was a wiring diagram printed on the inside of the condenser unit showing where the fan needed to be connected.

The wiring compartment in the condenser unit. Note the white cable is the new fan.
The wiring compartment in the condenser unit. Note the white cable is the new fan and the capacitor to the right of the image is from the old fan motor.

The next step was to put the top back on the condenser unit and screw the fan to the top. Once the fan was screwed to the top and the cables were tidied up the finished product looked like the following:

The finished product.
The finished product.

The only step left was to test the unit and make sure it worked properly. After turning on the unit the whole thing roared back into life which was extra pleasing as the temperature was about 35ºC. After running for about 15 minutes the house was at a cool 22ºC

More pictures
More Pictures
Air Con 2
More Pictures

Videos

Video of unit running immediately after installation

Unit running in heat six months after new fan installation