A/C Compressors?

[brobox]

Originally Posted by oneknight

Excellent stuff, just what I needed, thank you so much!

Jeanne is a walking encyclopedia when it comes to research and documentation. Pretty damn sharp on the technical stuff too, she has taught me a lot. I am still old school, she is more up to date that I am.

[Rollin101]

Jim, you said in your post compressor comes on cools for a while then shuts down and won’t restart until you turn the breaker off and back on.
If the compressor starts first time it’s 99% not the capacitors. If you have good airflow in the Mh you can rule out freeze sensor. Sounds like you hit on the problem with the over pressure switch. If the condenser on the roof is clean it’s probably a bad high pressure switch. I don’t remember if there’s a place you can jump around that switch without cutting wires.
Call ERIC at RVP 316 832-3446 and see if he can help you.

[oneknight]

Originally Posted by Rollin101

Jim, you said in your post compressor comes on cools for a while then shuts down and won’t restart until you turn the breaker off and back on.
If the compressor starts first time it’s 99% not the capacitors. If you have good airflow in the Mh you can rule out freeze sensor. Sounds like you hit on the problem with the over pressure switch. If the condenser on the roof is clean it’s probably a bad high pressure switch. I don’t remember if there’s a place you can jump around that switch without cutting wires.
Call ERIC at RVP 316 832-3446 and see if he can help you.

Thanks, and your thinking parallels mine exactly.

According to the schematic in the manual Jeanne posted, it is actually a current / temperature sensor. It is soldered into several coolant lines, no way to disturb it without dumping the system. It is a basic 2 wire normally closed switch, wires into a relay latch, right on the power feed to the compressor.

It should be easy to bypass by jumping across it. Not sure how good an idea that is.

Darned thing ran pretty good most of the day, cycling on and off normally, making lots of cold.

Till right after dinner. The compressor quit and it blew warm air again. Blah.

I'd really like it to misbehave in the middle of the day when I feel like going up there.

[Rollin101]

Originally Posted by oneknight

Thanks, and your thinking parallels mine exactly.

According to the schematic in the manual Jeanne posted, it is actually a current / temperature sensor. It is soldered into several coolant lines, no way to disturb it without dumping the system. It is a basic 2 wire normally closed switch, wires into a relay latch, right on the power feed to the compressor.

It should be easy to bypass by jumping across it. Not sure how good an idea that is.

Darned thing ran pretty good most of the day, cycling on and off normally, making lots of cold.

Till right after dinner. The compressor quit and it blew warm air again. Blah.

I'd really like it to misbehave in the middle of the day when I feel like going up there.

If it ran most of the day my money is on the switch being too sensitive. I would bypass it if it were mine. If your condenser is clean I’m relatively sure it’s not actually an over pressure. What have you got to lose? If the system operates normally with it bypassed you’ll have to make a decision to leave it bypassed or replace the unit. If it still doesn’t operate you have eliminated that part as the problem.

[oneknight]

Still struggling with this. Our recent trip north wasn't bad, it's still cool in Wisconsin, but we're back in E. TN now, and it's in the 90's.
I got one unit that cools all the time (#2), one that cools sometimes (#3) and #1 worked for 2 hours today, first time in 4 days plus.

Going up tomorrow with my meter and the attached schematic.

I talked my wife into coloring the wire colors, so I won't have any trouble following it up there.
I'm gonna have to disconnect the fan wires (may wire in a quick disconnect connector) because the relays and capacitors are under the fan blades.
But assuming it's still broke in the morning, I'll find the problem and jumper it out.

If anyone wants a hi res, I uploaded the file to the files page of the site, here iRV2 Forums - Files - AirXcel Mach 8 Heat Pump schematic

[oneknight]

Fixed.
I bypassed the pressure limit switch and relay on #1 & #3.
Everything cooling normally now. Yay!

[Magic-carpet]

Great..! So how did you bypass the those components. Just jumper across the posts 5 and 7 on the relay?

[oneknight]

Originally Posted by Magic-carpet

Great..! So how did you bypass the those components. Just jumper across the posts 5 and 7 on the relay?

Ya know, I took a picture...
I wish I'd taken a before, but didn't.

And then I thought about how the heck I'm going to explain this...
And didn't post it.
I know this problem is common, and lots of guys are paying $1200 or more plus install to replace perfectly good air conditioners with bad high pressure limit sensors or sticky relays.

But we're dealing with potentially lethal voltage and moving parts, on the roof of an RV 13 feet in the air. (and a bunch of rich old guys who should know better!)

This stuff is in the silver box under the fan.
I took the fan off the motor for all my testing!
I had to test this HOT, with a proper digital voltmeter, and my wife on the phone to turn the thermostat on and off, and listen for me to get zapped and fall of the roof.

Once you're in the box, there is a terminal board with a bunch of wires, in front of and below the capacitor (I'm behind the unit, facing forward.)
Pass side, there is a white and 2 yellow wires (on a triple terminal) this is your neutral in.

A couple over there is a purple wire, this is your "Turn on and make cold" wire"
If the thermostat is calling for cooling, you'll have 115AC from the yellow to the purple wires.

The "cool" signal goes here and there, and ends up as a black wire on pin 7 or the relay. The terminal is one of those "double ones" and one blue wire from the high pressure attaches to it.

"Cool" come out of the relay on pin 2, 2 black wires, one of which has one of those "double terminals" and the other blue wire connects here.

So... I took the blue wires off.

I used the double terminals to connect all 3 black wires together.
I plugged that into Pin 2 of the relay mostly just to control the wires, not have a hot wire flopping around inside the cabinet.

I attached my picture, which shows the 3 black wires, connected together, on the right side of the relay.

If anyone else tries to do this, be careful. Test first to ensure that is the cause of the problem. Be aware that bypassing a safety switch simply is not the right way to fix something.

[Magic-carpet]

Originally Posted by oneknight

Ya know, I took a picture...
I wish I'd taken a before, but didn't.

And then I thought about how the heck I'm going to explain this...
And didn't post it.
I know this problem is common, and lots of guys are paying $1200 or more plus install to replace perfectly good air conditioners with bad high pressure limit sensors or sticky relays.

But we're dealing with potentially lethal voltage and moving parts, on the roof of an RV 13 feet in the air. (and a bunch of rich old guys who should know better!)

This stuff is in the silver box under the fan.
I took the fan off the motor for all my testing!
I had to test this HOT, with a proper digital voltmeter, and my wife on the phone to turn the thermostat on and off, and listen for me to get zapped and fall of the roof.

Once you're in the box, there is a terminal board with a bunch of wires, in front of and below the capacitor (I'm behind the unit, facing forward.)
Pass side, there is a white and 2 yellow wires (on a triple terminal) this is your neutral in.

A couple over there is a purple wire, this is your "Turn on and make cold" wire"
If the thermostat is calling for cooling, you'll have 115AC from the yellow to the purple wires.

The "cool" signal goes here and there, and ends up as a black wire on pin 7 or the relay. The terminal is one of those "double ones" and one blue wire from the high pressure attaches to it.

"Cool" come out of the relay on pin 2, 2 black wires, one of which has one of those "double terminals" and the other blue wire connects here.

So... I took the blue wires off.

I used the double terminals to connect all 3 black wires together.
I plugged that into Pin 2 of the relay mostly just to control the wires, not have a hot wire flopping around inside the cabinet.

I attached my picture, which shows the 3 black wires, connected together, on the right side of the relay.

If anyone else tries to do this, be careful. Test first to ensure that is the cause of the problem. Be aware that bypassing a safety switch simply is not the right way to fix something.

So to recap, you took the pressure switch out of the loop by disconnecting it, attached the wire from post 7 to post 2 on the relay, and you ordered a couple new pressure switches today? maybe a couple of new relays also? I'd bet you ordered three of each? Maybe your units got a batch of bad switches? Is there a way to test a pressure switch?

[Rollin101]

Like I said earlier what have you got to lose. Personally, since the high pressure sw. is soldered in the system I’d leave it as is, but that’s just me. A lot of a/c systems don’t even have a high pressure switch.

[Magic-carpet]

Originally Posted by Rollin101

Like I said earlier what have you got to lose. Personally, since the high pressure sw. is soldered in the system I’d leave it as is, but that’s just me. A lot of a/c systems don’t even have a high pressure switch.

Yes, if its soldered in the system that's a different story. Too bad its not a screw on sort of setup to a schrader valve.

[Mwoodofd]

Thanks Jim and Jeanne, I'm going to take a look at my front AC that has demonstrated some of these symptoms. (another thread on here) While mine is a little older, worth a try before I spend the $1200 or so for a new one.

[oneknight]

Originally Posted by Mwoodofd

Thanks Jim and Jeanne, I'm going to take a look at my front AC that has demonstrated some of these symptoms. (another thread on here) While mine is a little older, worth a try before I spend the $1200 or so for a new one.

Run it til it blows warm air, shut it down, take off the cover, the fan blades, and the silver box cover, turn it back on, and check your voltage going through it.

In addition to the high pressure sensor, there is a freeze sensor on the tube coming out of the front of the compressor, and a compressor current/overheat sensor under a black cap actually on the front of the compressor.
Any of these could shut it down.

[oneknight]

Originally Posted by Magic-carpet

So to recap, you took the pressure switch out of the loop by disconnecting it, attached the wire from post 7 to post 2 on the relay, and you ordered a couple new pressure switches today? maybe a couple of new relays also? I'd bet you ordered three of each? Maybe your units got a batch of bad switches? Is there a way to test a pressure switch?

The pressure switch is soldered into the coolant line, it cannot be replaced.
I'm thinking the units will be just fine without it.