Compressor not starting Fujita split system

[alan_man]

Hi fellas, I recently removed/replaced an old Fujita split and decided to take the old split home for some fault finding. Its a Fujita AS-H12A4/HS, fixed speed compressor about 6 years old now (I'm aware Fujita is not the best quality). As I mentioned in another thread my licence does not allow me to fix and repair but I have this one sitting at my place and would like to learn more about service/fault finding etc split systems. I reclaimed approx 700g of R22 upon removal (spec plate states quantity of unit to be 720g) so ofcourse that rules out a refrigerant issue. Basically what was happening on both heating and cooling attempts the condensor fan will start up as well as evaporator fan (only on cooling obviously) but the compressor will not run. I could hear the compressor try to start, it would vibrate slightly for about 1-2 seconds then a relay would click and compressor would "stop". This would happen every say 10 seconds over and over. Any ideas what I should start testing first, capacitor etc and what the problem likely may be? Thanks in advance

[alan_man]

Ok done a few tests (may need to be corrected on), first with the compressor. Put a megger on the windings and got;
Went from Start lead to common lead and got approx 2.7 ohm
Went from Run lead to common lead and got approx 1.75 ohm
Went from Run lead to Start lead and got approx 4.45 ohm which adds up
I have never tested capacitors but had a quick look, it seems to be a 35microF/450VAC capacitor. There were a total of 4 terminals, seperated into 2 sets. On one set came the wire from the supply, and also a red wire that goes to the Run terminal of compressor. On the second set there was a yellow wire that goes to the Start terminal on compressor. The other terminal in this set was not used. I tested the capacitor disconnected and figured I'd go from each terminal that connects both Run and Start terminals. Ended up getting 1.675microF on my tester, which means? I got the same figure going from the terminal Run terminal to the unused terminal but nothing between the Run terminal and the supply terminal. Not sure what I should be getting and how readings are meant to be interpreted? I connected everything back up (including pipes and interconnect etc) and decided to clamp test each wire. I clamped the supply wire as well as each Run and Start wire from the cap to the compressor. Supply and Run (each red wire seperatley) reached approx 35 Amps each time the compressor tried to start for that 1-2 seconds, however did not get any reading on the Start wire (yellow wire) at all which seems odd to me, I thought It would be the other way around? Any way if someone can decipher this that would be great

[monkey spanners]

Try a new capacitor, old one sounds like its failed, they often have two pairs of terminals, so to ins and to outs in effect. Some capacitors also include the fan cap in the same can, this would be something like a 35uf/5uf for example. This could have three or six terminals depending on design.

Jon :)

[moondawn]

Could you check you are getting the correct voltage at the compressor windings

[Brian_UK]

I know that this isn't for your compressor but is a useful set of guidelines for compressor install and wiring etc...

http://hvac.amickracing.com/Compressor%20Information/Bristol%20Compressor%20A%20and%20B%20series%20instructions.pdf

[alan_man]

Bingo, changed the capacitor and the unit runs good as gold now. thanks for the replies and that pdf was a good read

[Brian_UK]

Good news and thanks for the update.

[moondawn]

whats the plan for the now working system?

[alan_man]

whats the plan for the now working system?

Well the unit has been evacuated, recharged and pumped down. A friends wants to install it in a granny flat he has at his house so I will probably pass it off to him. If you were in Australia and were interested we could have worked something out

[Karl Hofmann]

That's going to be one hell of a callout charge Alf, the OP is in Austrailia...... Can you smell SPAM cooking?

[Icedvovo]

I just joined up to say - Thank you Thank you Thank you!!

You guys just saved me a fortune!

I had the exact same problem on a 38 degree day and after reading this thread I figured it was worth it to change the capacitor. And it worked!

Thank you guys! Saved me a lot of money and a lot of work. Woohoo!

Beer?