How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Douglas Your Own Question
Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
Type Your HVAC Question Here...
Douglas is online now
A new question is answered every 9 seconds


Customer Question

Manufactured 4/2006 - Install date 6/26/2006 - Standard Limited Warranty 5 years, (just missed the cutoff) Units serviced within last 5 weeks for winter use. Installed a new Honeywell Model 8500 Programmable Thermostat about a week ago. No issues after install. Everything was running fine until.... This morning woke to the sound of a LOUD one second HUM that repeated every 60 seconds or so, was coming from compressor unit. Called HVAC dealer and had them come in to look. Tech Tried to swap out start/run cap, but used a slightly undersized one to test, (had blower fan disconnected at the time) did not cure the no start condition. Tech checked all contacts and connections. Amp draw showed a 10.3A amprobe draw each time it attempted to start up. Tech checked a few voltages here and thre but didn't verbalize them. Final diagnosis was a faulty compressor. Alliance Model SPR036B1RPA Ser # XXXXX Estimated price to replace $12-1400.00. So... heres my question: How can I be SURE it's really the compressor, was the tech as thorough as he could have been to diagnose, is there more I can check ( I am well versed in automotive a/c and have done some HVAC work on my homes now and then, I have gauges, a probe and vacuum pump) and if so WHERE can I find a supplier that I can get the part from. No luck finding one on the net.
Submitted: 4 years ago.
Category: HVAC
Expert:  mranswer replied 4 years ago.
Diagnosing a compressor is no different than diagnosing a motor. If you have the right voltage to it and the capacitor is good and it does not start then it's bad. Sounds like the tech did the right checks the right way here. A slightly undersized capacitor would have made this start. No one is going to sell you a Trane compressor as that is something sold only to authorized servicers, so it looks like you would need to pay someone here to do it or just replace the whole unit. You may be able to buy a new unit as some dealers do not care who they sell to, but that investigation is on you to do by getting on the phone and calling the local folks.
Customer: replied 4 years ago.
Relist: Answer quality.
Added no value, made assumptions when asked for specifics, opinionated.
Expert:  Douglas replied 4 years ago.

Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment.


I would ask specifically what the actual reading in microfarads the run capacitor shows. It should read within 10% of the rating printed on it. I would aslo ask what the resistance readings are at the compressor. Run to Start, Run to Common and Start to Common. What are the voltages to the compressor (not to the contactor)


Chances are if he tried a replacement hard start kit and it didnt start it's locked up but 10 amps does not really suggest a locked up compressor. Maybe he was reading on the start circuit rather than common. I would expect to hear 30-40 amps and possibly a tripped breaker.


If in the end the compressor is locked up, and I am aware you didnt like the previous answer but you will be hard pressed to purchase a replacement Trane Compressor from a Trane distributor. They are wholesale only and their day to day customers (contractors) would come down hard on them for bypassing them and 1 small sale is not worth it to them.


12-1400 is on the low end of what it would cost to have someone install an out of warranty compressor.

Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience: Manufacture Rep for Major Brand, Technical Trainer, NATE
Douglas and other HVAC Specialists are ready to help you
Customer: replied 4 years ago.

Three wires, thick Red, thick Black, thin orange, I had to ask him to amprobe the thick red. He didn't even take the initiative... that's what is bothering me, it almost sounded like it wanted to start but the cap wasn't providing the initial boost. Interesting though how an Alliance compressor part is impossible to buy, I can buy the cap no problem, a GE part # XXXXX $26 bucks. Frustrates the hell out of me. If I could get all the materials I could fix this myself in under two hours for about half the price. I'm tempted to buy the cap and gamble the $30 bucks. I will check the voltages and get back to you, Is that OK? and thanks...

Customer: replied 4 years ago.
I went and did a few more measurements.

Amprobe at attempted start is 100.3 Amps on each leg. (red & black) - 5 readings taken

Impedances between all C -S - R terminals on compressor are < 1 ohm multiple readings at each pair.combination.

After hooking everything back up I rechecked all terminals and connectors even back to the breaker.

attempted to start, same symptoms but now the contactors are buzzing LOUD.

I found the compressor, of all places... $1000.00 retail. updated part #. HVAC contractor wants $1600.00 for compressor, cap, contactor, freon, dryer and nitrogen purge, vacuum, leak check and R-22 fill. not an un reasonable price BUT only 1 year on parts warranty.
Customer: replied 4 years ago.

I powered off the unit, took ohm readings - C -S -R terminals on compressor terminals all under one ohm. I went and checked the contactors, they look clean. I tightened all screw down connections back to the breaker also. checked all voltages at multiple points. all look good. I hooked everything back up and tried unit again at thermo, call for heat with no aux heat strips coming online. No buzzing this time, DIfferent sound now, Not a HUM but more like an attempted start,I can HEAR the compressor *try* to start every 15 or so seconds. It's not seized. I hear the scroll moving for about a second at each attempted start up. The orange start wire off the CAP is showing a 3 AMP draw. I read a 14V leak to ground from the casing of the cap while energized.