Compressor Doesn't Start Reliably (tech claims theormstat is problem???)

[Shophound]

Originally posted by secstate

Originally posted by tinknocker service tech
75/185 at 85 degrees outside and cooling fine
i must be missing something what did he say was wrong with the compressor and did he install a hard start kit

No hard start kit installed (at least since I have owned the house which is about two years). First tech said the problem was a "cracked valve" the second tech said "worn valves".

Have either of the technicians that's been out bothered to clean the condenser coils? Whether or not this is a direct contributor to your troubles, if you plan to keep this condenser and swap out the compressor, the outdoor and indoor coils should be cleaned.

If I were the technician at your home here's what I would check before condemning the compressor:

a) Allow compressor to start and run normally. Observe startup and running amperage draw.

b) Record pressures, superheat, and subcooling readings after system has been online awhile and has balanced out. Check temperature of lines across reversing valve to indicate any bypassing of refrigerant.

c) Note temperature rise over outdoor coil.

d) Note temperature drop over indoor coil.

e) Note condition of outdoor and indoor coils, and condition of indoor blower wheel. Note any restrictions to indoor air flow (return duct collapse, supply register dampers closed, etc)

f) De-engergize system and observe time involved for system to equalize. Note whether system uses TXV or piston in either or both coil sections (being a heat pump).

g) Check strength of capacitor.

h) Check integrity of compressor motor windings.

i) Check condition of compressor contactor.

j) Check condition of compressor terminals for any corrosion or burning of wires.

k) Backwash condenser coils.

l) Restart unit and observe all conditions after balance-out.

m) Stop unit and allow five minutes to equalize. Restart.

0) Give customer options according to my findings.


That might seem like a lot for a tech to do on a service call where he feels rushed for time due to a high stack of tickets sitting in the passenger seat of his van. If he's experienced and skilled he can knock out these checks with ease and arrive at an informed diagnosis rather than tossing out "Uh...sometimes they just do that."

[secstate]

Shophound thanks. I guess I am on to tech number three. They haven't done anything near that. Neither tech bothered to even look at the evaporator inside. No mention of coils or cleaning of coils for sure. Any advice on finding a competent tech wiling to do this or getting a tech to do this? Asking neighbors and looking at certifcations (i.e, Trane comfort specialist havent' helped).

[tinknocker service tech]

every thing shop hound said is or should be standart check befoere you condem a compressor. it realy does not take a long time and if done properly you will know the reason the compressor is going bad. cleaning the outside coil is not a hard or time comsuming thing. my consern is since i am going by presure alone 75/185 at 85 degrees is not showing bad valves. with out superheat and subcooling dont realy know what is going on in the system but the valves are not showing blow by to me. as far as starting is the cap weak did they even test it. is the contactor pitted and burnt. about ten years ago a tech condemed a compressor because it wouldnt start. he installed a new one and guess what wouldnt start. i was sent out before a third one was put in and contactor was so pitted couldnt get enough voltage to start the compressor but the fan ran
changed the contactor and it still works. if compressor is having trouble starting a hard start kit will not hurt it and a time delay will also help to
you have two differant readings from two differant techs and something just isnt making sense to me. not trying to be a smart ass but in my opioun something esle is goig on and the compressor isnt it

[secstate]

Originally posted by tinknocker service tech
is the contactor pitted and burnt. about ten years ago a tech condemed a compressor because it wouldnt start. he installed a new one and guess what wouldnt start. i was sent out before a third one was put in and contactor was so pitted couldnt get enough voltage to start the compressor but the fan ran

You are an absolute genius! I went out to clean the coils today (they weren't bad at all). While there I decided to look at the contactor. I may not know much about AC units or thermodynamics but I do know a lot about electrical/electronics and the contactor's contacts were so pitted and there was so much carbon that I am shocked that the thing comes on at all.

[chillbilly]

That compressor doth protest a bit too loudly.

[tinknocker service tech]

no lucky guess if this is the problem
i would recomend haveing a hard start kit installed with a time delay on break. this will relieve any problems if the unit is trying to start under heavy losd conditions.