Goodman condenser does not build head pressure, bad compressor?

[plain garage]

We have a Goodman 3 ton condenser with a Bristol recip compressor going on 15+ years, it has a 1-pole 40amp 240/24vac contactor, and 2 separate capacitors (fan motor and compressor). It has ran low on charge before, usually a recharge will bring it back to life.

This time, it won't take any charge, and the head pressure is the same as the suction pressure around 100psi, even with both the fan and compressor running. The air handler blower comes on fine but it just blows hot air. I climbed in the attic to check on the metering device, it sure did not have a TXV.

Has the compressor kicked the bucket? How can I test to confirm? Budget is tight right so I prefer to replace components instead of full system. If a new compressor will yield a few more years of life, I'd go that route, have the system vacuumed, evacuated, compressor brazed in and nitrogen tested for leaked then refilled.

 

[bazar01]

Has the compressor kicked the bucket? How can I test to confirm?

1. Put a clamp ammeter on one leg of the 230V power feed below the contactor to confirm the compressor is running. It should be over 20amps if compressor motor is running.
If just the fan is running, it will read around 2 amps.

2. If compressor is not running, it probably tripped on overload. You have to wait until it cools down then test it again if it will come back to life.
Good luck!

3. If compressor is confirmed running, loss of head pressure means the valve plates are bad. It will need a new compressor.

Report back your findings.

 

[brewchief]

1. Put a clamp ammeter on one leg of the 230V power feed below the contactor to confirm the compressor is running. It should be over 20amps if compressor motor is running.
If just the fan is running, it will read around 2 amps.

2. If compressor is not running, it probably tripped on overload. You have to wait until it cools down then test it again if it will come back to life.
Good luck!

3. If compressor is confirmed running, loss of head pressure means the valve plates are bad. It will need a new compressor.

Report back your findings.

This is a good start, if the compressor is running I would be planning on a complete system, no way I would install a new compressor on a 15 year old system that is a known leaker.

 

[zmaxmotorsports]

How much freon did you put in it,whats the suction line pressure?
Before Id waste money on a compressor Id get a dry r22 condensor and install it as long as you can find the leak and fix it,then have it recharged.
If the leak is in the A-coil and the compressor is cooked Id just go with a 410a system.
Lots of questions to answer before biting the bullet.

 

[plain garage]

Armed with my ammeter, I went outside in the 83 degree sun. Surprisingly the compressor now won't start, nor does the fan. The ammeter around the T1/T2 wire showed only 0.7 The contacter plunger engages fine when thermostat is turned to cool. This is different from what happened the other day, when the system slowly took 1 lb with both compressor and fan running, the system capacity is 76oz according to the plate.

So without the outdoor system operating and both king valves in midseat, the standing pressure is 0 psi on the suction side and 50 psi on the liquid side, the indoor blower still comes on.

This really puzzles me, what can make the fan and compressor not start now since it just ran few days ago, though it didn't build any pressure at the time. Should I ohm the capacitors next? or just replace them (there are two) and the contacter?

 

[brewchief]

King valves on a gooman ? Never seen that, only residential A/C I see with king valves are some older Carrier. If they are the regular service valves that you remove the caps and use a 3/16 and 5/16 Allen wrench on then they should always be backed all the way out, the service ports have Schrader valves in them.

Sent from my XT1254 using Tapatalk

 

[plain garage]

They are service valves, back seated before disconnect, but cracked open to read the press.

 

[brewchief]

They are service valves, back seated before disconnect, but cracked open to read the press.

Post a pic, I've ripped out tons of goomans over the years and never seen one with a service valve that needed to be opened to read the pressure.

 

[Stuff]

Dumb question but have you been trying to run the system with the service valves closed? That is one way to destroy a compressor.

Also I thought that most home systems (non heat pump) do not have any check valves so pressure in liquid and suction should equalize a while after the compressor stops. How sure are you of your gauges?

 

[plain garage]

If someone needed to pump down their system, the service valve should be closed, not the case here. If there's a restriction in the system, that would explain uneven pressure no?

 

[LS6 Tommy]

Just because the contactor pulls in you don't know you have power to the unit.
The transformer is not in the condensing unit. The breaker may be tripped.

Check for line voltage at L1 & L2 with the contactor. Do you have proper line voltage? If so, do the same with the contactor energized. Same readings? Do the same between L1 to ground and L2 to ground. Still the same?
With the contactor energized, what is the voltage between T1 & T2? T1 and then T2 each to ground? Still good?

If the compressor was going bad it may have seized and the internal overload was open, but that doesn't explain the condenser fan not running. You may have also burned the contactor pads out and it no longer conducts.

Sometimes I wish I could be with you guys for this stuff. It's usually faster to just run the diagnostics than it is to talk someone through them.

Tommy

 

[Ohmthis]

I agree with tommy, look for a bad or tripped breaker. WARNING please shut off power before doing these checks!!!You can also ohm out the windings of a compressor to see if they are weak or bad. Find the wiring diagram and see which wires are to the compressor, there should be three, common, start, and run. You may have to remove the start off of the capacitor. Go from start to common (write this number down), then run to common (write down), and finally start to run (again write down) the start to common and run to common should equal (add these two numbers) the run to start. If they don't or you have an open, the compressor windings are bad. Also check the capacitors for both the fan and compressors. They go out pretty common and can have these symptoms. Good luck.

 

[LS6 Tommy]

I would add to Ohmthis' post to check each winding to ground. The easiest way to do this is to put one meter probe on the compressor terminal and the other probe on a clean, bare spot on the copper suction or discharge lines. Always check the windings with the wires disconnected.

BE CAREFUL WHEN DISCONNECTING THE WIRES FROM THE TERMINALS. The terminal plug can blow out under refrigerant pressure after a burnout. It's rare, but it can happen. Don't hamfist anything.

Tommy

 

[zmaxmotorsports]

Dumb question but have you been trying to run the system with the service valves closed? That is one way to destroy a compressor.

Also I thought that most home systems (non heat pump) do not have any check valves so pressure in liquid and suction should equalize a while after the compressor stops. How sure are you of your gauges?

And now the rest of the story!

 

[zmaxmotorsports]

Just because the contactor pulls in you don't know you have power to the unit.
The transformer is not in the condensing unit. The breaker may be tripped.

Check for line voltage at L1 & L2 with the contactor. Do you have proper line voltage? If so, do the same with the contactor energized. Same readings? Do the same between L1 to ground and L2 to ground. Still the same?
With the contactor energized, what is the voltage between T1 & T2? T1 and then T2 each to ground? Still good?

If the compressor was going bad it may have seized and the internal overload was open, but that doesn't explain the condenser fan not running. You may have also burned the contactor pads out and it no longer conducts.

Sometimes I wish I could be with you guys for this stuff. It's usually faster to just run the diagnostics than it is to talk someone through them.

Tommy

 

[zmaxmotorsports]

So the 1st thing Id suggest after learning more of the details is to make sure the service valves are both open.
Then Id make sure you have 240ish volts getting to the condensing unit.
If your getting 240 to the load side of the contactor when the coil pulls in and the fan and compressor still wont start Id check the capacitors,But it would be strange to lose 2 seperate caps like youve got there.

 

[Ohmthis]

Z, I've seen a fan motor run with a very weak cap (.9MFD on a 5 MFD cap), but never have seen one run with a bad one. There is a chance that the compressor cap was already bad and then the fan cap crapped the bed. It's something to look at

 

[bazar01]

They are service valves, back seated before disconnect, but cracked open to read the press.

The service valves are always back seated (turned all the way to the top) and service ports are open to read pressures.

Do not give up yet.
Make sure the service valves are both back seated and hook up your gauge.
Report the pressures.

Then these guys can walk you through the next steps.

 

[Brian_WK]

Sometimes I wish I could be with you guys for this stuff. It's usually faster to just run the diagnostics than it is to talk someone through them.

Tommy

Remote trouble shooting *****. I was helping a buddy of mine trouble shoot his A/C. Started as texts/ pics moved to phone call then video chat. After all of that I still bit the bullet and drove the 20 miles to check it out. Bad contactor/ Spider under the points. Something so simple and easy to find in person but impossible to see over the phone. So I changed it when I was there.

Your on the right track here but you definitely need to get some info straight.
1.If they are typical service valve on a residential unit it needs to be completely back seated or threaded up. Threaded all the way in will only allow you to see the pressure in the line set. Which will be isolated from the condensing unit.
2.Start checking your voltage at the disconnect and move towards the components when you lose your power thats where your problem is. If you have power all the way to the compressor. Its the compressor.
3.Pretty much all other advice in this thread is spot on and should lead you to your problem. Some of it does get quite involved and is just to prove that the compressor is bad.


Brian

 

[acmikee]

if the compressor is running and the suction pressure and discharge pressure are the same you have bad valves need to replace the compressor..
if your reading .7amp check your voltage L1 to L2. i'll be its 0V..........

 

[plain garage]

Thanks f or all the advise, I took more measurements, and it's looking weirder again. L1 to ground is 120v, L2 to ground also 120v, but L1 to L2 when contactor is energized is 600mV, and with contactor non-energized it's 68v. It looks like the 2 lines coming to the condenser are off the same phase??

So I went back inside to the main breaker, verified the ac circuit is a double pole 40amp breaker, each leg to ground is 120v and cross leg is 209v. So the only thing sitting in between main ac breaker and L1/L2 on the contactor is a disconnect/breaker box next to the outside unit. It's on a 30amp breaker but I couldn't take the panel off the inspect the wires inside.

One thing to note is they used 2 s separate 10awg wires from main breaker to outside box run inside a conduit. Also when contactor is energized the T1 to T2 voltage was also around 500mV.

Can I swap the 1 pole contactor for a 2 pole? I will try to open the outdoor box but it's so odd to have 240v turned into 120 like that...

 

[brewchief]

Thanks f or all the advise, I took more measurements, and it's looking weirder again. L1 to ground is 120v, L2 to ground also 120v, but L1 to L2 when contactor is energized is 600mV, and with contactor non-energized it's 68v. It looks like the 2 lines coming to the condenser are off the same phase??

So I went back inside to the main breaker, verified the ac circuit is a double pole 40amp breaker, each leg to ground is 120v and cross leg is 209v. So the only thing sitting in between main ac breaker and L1/L2 on the contactor is a disconnect/breaker box next to the outside unit. It's on a 30amp breaker but I couldn't take the panel off the inspect the wires inside.

One thing to note is they used 2 s separate 10awg wires from main breaker to outside box run inside a conduit. Also when contactor is energized the T1 to T2 voltage was also around 500mV.

Can I swap the 1 pole contactor for a 2 pole? I will try to open the outdoor box but it's so odd to have 240v turned into 120 like that...

I think it's backfeeding though the unit giving you the strange voltage readings, open up the disconnect and see whats going on in there.

 

[LS6 Tommy]

I think it's backfeeding though the unit giving you the strange voltage readings, open up the disconnect and see whats going on in there.

X2.

Tommy

 

[zmaxmotorsports]

Z, I've seen a fan motor run with a very weak cap (.9MFD on a 5 MFD cap), but never have seen one run with a bad one. There is a chance that the compressor cap was already bad and then the fan cap crapped the bed. It's something to look at

Id say buy a lottery ticket if youre lucky enough to get one to run with .9 mf,I guess anything is possible though.

 

[zmaxmotorsports]

Thanks f or all the advise, I took more measurements, and it's looking weirder again. L1 to ground is 120v, L2 to ground also 120v, but L1 to L2 when contactor is energized is 600mV, and with contactor non-energized it's 68v. It looks like the 2 lines coming to the condenser are off the same phase??

So I went back inside to the main breaker, verified the ac circuit is a double pole 40amp breaker, each leg to ground is 120v and cross leg is 209v. So the only thing sitting in between main ac breaker and L1/L2 on the contactor is a disconnect/breaker box next to the outside unit. It's on a 30amp breaker but I couldn't take the panel off the inspect the wires inside.

One thing to note is they used 2 s separate 10awg wires from main breaker to outside box run inside a conduit. Also when contactor is energized the T1 to T2 voltage was also around 500mV.

Can I swap the 1 pole contactor for a 2 pole? I will try to open the outdoor box but it's so odd to have 240v turned into 120 like that...

Is this on a commercial building? 208 is not common residential voltage around here anyway.
Did you get 208 at the line side of contactor across the 2 leads coming in?

 

[plain garage]

Is this on a commercial building? 208 is not common residential voltage around here anyway.
Did you get 208 at the line side of contactor across the 2 leads coming in?

It's a residential unit, I measured across the two screws of the 40amp breaker in the main panel. I suppose I can measure across the buses the circuit actually stabs into to see what's coming into the house. My main concern is why there's no voltage across L2 and L2 at the contactor. It's looking more and more like an issue with the breaker box outside. Its seen better days.

 

[justsam]

Time to put away gauges and valve tools until you get a solid 240vac on both sides of the contractor.

 

[acmikee]

go to your outside breaker. pull off the cover with the breaker on measure L1 to T1 should be 0V... now do L2 to T2 should be 0V..... measure L1 to L2 should be 208V... now measure T1 to T2 should be 208V....

 

[justsam]

go to your outside breaker. pull off the cover with the breaker on measure L1 to T1 should be 0V... now do L2 to T2 should be 0V..... measure L1 to L2 should be 208V... now measure T1 to T2 should be 208V....

Make that 240 vac, there in no 208 anymore, unless three phase.

 

[plain garage]

The weather got hot again so I motivated myself to get the electric box swapped, now the voltage across L1/L2 and T1/T2 are 207V and the compress and fan both kick on when calling for cool. I checked the voltage at the main panel feeder cables, it's 208V, not 230V. I also put an ammeter to the line to compressor it's 6.8A, to fan is 1.4A.

Again, the low and high side pressures are 0 psi, with compressor ON or OFF. I tried back seating the valves and mid-seating them, same thing, 0 psi. The suction line doesn't seem to take any gas, is there a valve in the compressor that can cause that? I'm thinking maybe the shraeder valve on the service ports are clogged??

I know this is an old system, but if I can get it kicking again, I could just save enough money to get myself some more tools for the garage. Isn't that what we're all here for

 

[Milton Shaw]

Make sure your hoses have not been reversed on the gauge set. The end that attaches to the unit should have the valve core depressor inside the rubber seal. Sounds like they have been reversed and not depressing the schrader valves. The end at the gauges (usually straight) just has the rubber seal inside not he brass valve depressor inside them. Replace the battery in your meter to be sure it's not affecting the readings. Like others have said 208 is normally a commercial 3 phase reading.

 

[acmikee]

giving us the running amps is useless with out giving is the FLA.
I don't think your gauges are hook up correctly.