Tuesday, May 28, 2019

Preparing for Ford Nationals - AC Part 11 - System Charging

I took the Mustang in to a local automotive shop who agreed to charge the new air conditioning system.  I left the Mustang there and returned later to discuss how things worked out with the business owner.  He informed me of the following:

1) The system charged fine and everything is sealed properly.  The instructions stated that it would take 1.5 lbs of 134A but they checked and indicated the best cooling performance was at 1.25 lbs of refrigerant.  

2) My electric fan must turn on when the air conditioning is on and does not.  They stated that the A/C running until the engine warms up could damage the system.  It builds pressure incredibly fast when not cooled properly.

3) They suggested that there be some type of seals be placed between the condenser and the radiator.  With the fan behind the radiator, it can pull air around the condenser rather than through it due to the gaps around the side.  This will cause the system to run hot.  They indicated they can be block of panels of any type including high temp foam.

4) They were not certain if the cooling system would be enough to keep everything cool.  Unfortunately, I will not know if the A/C system is generating too much pressure from being too hot. 

In the end, they stated it is charged but I can't use it or it will damage the system.  This was very discouraging but I suppose I should be glad that thee were no issues with a leak.  This tells me at least my installation was done properly.

In my research, I found you should use a trinary switch when using an electric fan which is installed in the line between the condenser and receiver/dryer.  They are only $30 so that is not bad but I expect it will release the refrigerant when replaced which I just paid $175 to have filled.  I've gone through the Classic Auto Air instructions numerous times and it states nothing about it at all.  I tried to call but their tech line closes at 5PM.

I'm rather discouraged as everything for this trip to Tulsa is costing a fortune.  

05/29/19 Update:

I spoke with Steve (x8024) at Classic Auto Air this morning.  He stated the show I used is correct that head pressure will build very quickly in a state as hot as Texas.  It will likely build much faster than the engine temperature and would require the fan be on anytime the A/C is running.  He indicated the shop must be a good one if they managed to reach this conclusion.  He suggested I use a trinary switch to activate the fan.  He stated they use part number SW 4082C which turns on the fan at 254 psi.


He stated that if it were a secondary accessory fan I could use the wire which runs to the compressor.  This would trigger the fan when the compressor is running but is not ideal.  It does not clools down the system entirely before it cycles back on.  He was not sure if I went this direction if the compressor wire was a positive or negative trigger.


I asked that he put in a suggestion that the instructions be updated to simply state a note that a trinary switch may be necessary if an electric fan is in use.  He did not argue with me but acted as if only 25% of people have an electric fan.  There might certainly be true but then 25% of their customers who install the system based on the instructions pay twice to have refrigerant added. In the end, I dropped it as it did not seem that the suggestion would be taken.

I ordered the trinary switch this morning from Amazon and it will be here tomorrow.  I'll wire up the connector in the car, remove the valence so it is easily accessible, and then take it back to the shop.  I'll have them evacuate the system, swap in the trinary switch, and then recharge the system.  I'd like to get some block off plates and maybe a fan installed first.  They can then tell me based on head pressure how well the cooling system is up to the task of keeping everything cool.

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