Hi there,

I am trying to fix an old Goettl gas pack unit. It worked fine till 2 weeks ago. Now it starts normally with colder air for like 4-5 minutes then it sends inside warm air , no cooling . From outside I can see the condenser fan blade starting to rotate for those 4-5 minutes , low RPM I`d say, then it stops .
A HVAC technician checked it and said it needs replaced the condenser fan motor which gets hot and that would cost $400 . This is expensive I`d say. So I decided I can find a new motor and I`ll do it myself for less :) . That`s how I`ve found this excellent site and I must say You guys are doing a really great job here.

The details now: this unit appears to be a very old 2 ton Goettl gas pack (don`t have its model#) . The condenser fan motor is not the original one, it has now a GE model 5KCP39KG S177AS (or 5177AS) 1/3HP 1075 RPM 230V 2.4A . I don`t know when it was last time fixed/changed, we`ve moved here 1 year ago. Talked to the Parts Sales at Goettl and was told there that for such 2 ton units the original condenser fan motor was a 1/5HP one. I also found inside of the unit a big capacitor (Run cap I guess) of 35uf - 440VAC and a smaller one (black) with contactor near it (the start one) at 88 - 108 MFD 330V. Took them out both and showed them at Goettl and was told there these would be original parts. Looks like all summer this unit ran like this: with these probably original capacitors for the initial 1/5 HP motor and the newer fan motor at 1/3 HP. Although last summer too was hot here in Arizona this unit was not used intensively.
I`ve tested the capacitors with a cheap analog Ohm meter - initially it goes to 10 KOhms then to infinite (for the big one - Run cap) and for the small black one (Start cap) initially goes to 2 KOhms then toward 10 KOhms and remains at 10 KOhms but not to infinite . I would think that the Start cap appears to be bad, I`ll change it. So far I haven`t dismantled the motor , will first try to replace both these capacitors, they are not so expensive.

Here is my issue: I can`t find any indication about the necessary Start capacitor for this motor . I assume the original capacitors values (as above) found in the unit are not the exact fit for the current motor (more powerful, as above). On the motor label it only says CAP 400/370 together with the above values , nothing else. I (I don`t know what it means). I was unable to find the specs for this motor (GE model 5KCP39KG 5177AS) nor its values for these capacitors. I`ve found similar motors requiring 5 MFD cap - I assume it`s about the Run cap .

I`d be grateful if any suggestions about these 2 values: Run Cap and Start Cap in my case.

Thank you for all your work.


muntii_nostri

The start and run caps you mentioned are probably for the compressor not the condenser fan motor. Usually the condenser fan motor only has a run cpacitor. Now the large silver run capacitor that is used for the compressor could also be used as the run capacitor for the condenser fan. This style capacitor will have 3 terminals instead of 2 terminals. The center terminal is usually common with one of each end terminals for the compresssor (higher MFD) and the condenser fan motor lower MFD value.

Unless the value for the replacement capacitor is listed on the motor or can be read on the present capacitor you might be out of luck unless you can find the motor model listed somewhere. The only other trick I have used before is to start with a 5 MFD and fire up the fan motor then us a Amprobe to test for amp draw to see if it is within spec for the draw listed on the motor. If not then try a 7.5 MFD.

If the motor has been stressed all summer it might be better just to replace it and the capacitor that works with the new motor all at the same time. It is never recommended to use the old fan motor run capacitor over with a new motor. Always replace the capacitor when replacing the motor (no exceptions).

There is a wide selection of replacement condenser fan motors available in the market place. I suggest that if you can find the correct HP,RPM,and rotation (many times reversible) that you just replace the motor and solve all the problems at one time.

Thank you for your quick reply and for your advice hvac1000 .
I`ve dismantled the fan motor and will replace it probably with one with the original size 1/5 hp . The original wiring was modified. The unit is an old Goettl GA 2-1A . I was unable to find any schematics of it. I`ll try at Goettl maybe they have some documentation about these units. I`d need this unit to work for another 2-3 years. I`ll come back with details.
Thank you.
m_n

One thing to keep in mind, if the condensing fan blade was changed when the OEM motor was replaced then you might want to go back in with a motor the same specs as the replacement. The blade is designed to work with a motor of certain specs.

Since you might not have a way of checking is the pitch and size is the same as the original you might want to consider a visit to a electric motor rebuild shop. They have the proper tools to be able to tell you what Horse Power you need to turn the condenser fan blade you have on the unit now.

Actually the motor should be matched to the requirements of the equipment then the fan blade matched to the motor. That is the way the factory engineers do it. The matching set is calculated on the draw end and how many fins per inch and thickness are the condenser coils designed to be to remove the condenser heat load.

True, my local Johnstone guy is pretty good at matching blade to motor and vise versa.

To bad in this area Johnstone will not talk to anyone but a dealer. They are strict here.

Thank you both for the hints. I`ll change with a motor of 1/3 hp - I succeeded in recovering both the mount for it and the blade too (Torrington - aluminium 18in diameter 5 blades, pitch approx. 35 degrees) . Comparing with other blades found on Internet - 3 blades and lower pitches at comparable diameter and rpm it looks like it needs a powerful motor so I`ll keep it at 1/3 hp. I`ve seen other similar units on the roofs around and it looks like the original blade this Torrington one. Can`t imagine this blade working with 1/5 hp, at least not at 1075 rpm. Tomorrow I`ll search for a new motor, however I`m thinking firstly to check if maybe worthy just to rewire this old one. And by the way - here too Johnstone would talk only with a dealer. :(
I`ll come back with new details.

m_n

I had the same problem with Johnstone when I first graduated from tech school. I was just doing side jobs while I looked for an actual job. I went to the local Johnstone and opened up a cash account. Just made up a company name and they sold to me no problem, of course I didn't get the same discount but I could buy parts.

Hi again,

Pretty late but I finished yesterday with the fixing af the old Goettl. I`ve replaced the fan motor with an AOSmith 1/3hp 1075 rpm, max ambiental temperature 60 degrees Celsius. I`ve used the original mount and blade, put a new start condenser for it. Some excitement at the final test: I was able to start the conditioner manually pushing the tab of a relay I found inside but it wouldn`t start controlled from inside the house. I was thinking that I`ve fixed the fan motor but I`ve maybe broken something else... It proved to be the thermostat in the house which I knew it worked fine so far but was remained set as for the summer while the temperature here in AZ decreased in the meantime below the summer set one :) After changing the setting everything worked fine.

So... happy end ! For now at least :) . I was asked initially $400. Doing it myself costed about $135 plus some work, I chose a better motor (not chinese and for some higher temperature) and I`ve also got some basic knowledge about air conditioners. Totally worthy from my point of view.

Hvac100 and MarkwithaK thank you for all your help. The information from you helped me doing this step by step.
Hoping there will be no other issues with this air conditioner this year :) I`ll wish you both a "Happy New Year!" and "Happy Holliday!".

Cheers,

m_n

Same back to you and glad you finally got it going.

What he said.