Tuesday, September 5, 2017
Didn't expect my blog to become an HVAC repair guide, but life brings what it wants to.
My rental house full of young "adults" and I get the call the AC isn't working on a warm day.
They say the inside unit is running, air is blowing, and the fan outside on the heat pump condenser is also running normally. But it is still warm. Is it low freon or a blown compressor? I hope not, that will blow months of rent money earned.
I go check it out and there is moisture on the unit and floor, it is sweaty and the insulated freon pipe to the outside is all sweaty and dripping, even icy in spots.
The air filter is sopping wet and wont come out, it seems stuck in the unit and too soggy to pull out.
I take off the cover of the air handler inside (the lower one) and instantly see the issue. The whole coil is a humongous block of ice. Wish i took a picture. A little quizzing of the occupants and I get an admission that somebody turned the AC down to 60 because they were hot.
It's possible that there is low freon, but i'm betting this is user error. I left them with the fan running and the AC unit off, telling them it will be 2 days to melt that mess. Luckily it is only 80 today and supposed to be cooler tomorrow.
Went back after three days, luckily the weather was cool so the lack of A/C didn't get any complaints. I replaced the filter and checked the coil. All back to normal. Turned on the A/C and it worked fine and cooled normally. No harm done. Whew.
Posted by siliconfish at 9:00 PM
Thursday, April 20, 2017
Not a lot of pictures here because i didn't think this fix would be the epic that it was.
The system is a generic International Comfort Products. Inside the box I found that Trane, Tempstar, Heil and ICP units use a lot of the same parts. So pretty much ignore the brand name on the unit.
First hot day in a while and the wife switches the heat pump to cooling mode and when I get home she complains it is not cooling.
Quick inspection reveals warm air blowing and the outside unit - condenser - is not running when the thermostat says it is cooling. The strangest thing is the condenser outside is quiet except for a fairly loud clicking about once every 2-3 seconds.
The solution was that the solenoid for the reversing valve (inside the outside condenser) was bad. It was shorted out. Replacing it is easy and can be done by opening the unit and removing one nut and plugging in the wires. Cost was less than $15 and can be done with only a socket wrench.
Here is how i figured it out... I bit of a comedy of errors but I got there in the end.
Google searching doesn't help. So i decide to start swapping parts.
I open the access panel on the outside of the condenser. With my finger feeling i discover that one of the relays on the control board is doing the clicking. My voltmeter shows the unit is getting both 240V and 24V power. The contactor (big relay) coil is not powered, so something is not telling the unit to start.
I decided the control board might be broken and ordered one on ebay for $20.
Heil Tempstar Defrost Control Board 1087952 CEPL130547-01 CEBD430547-02A
Picture of the contactor on the left, and the control board on the right.
When the control board came a few days later i swapped it in. all the connections are pull off and plug back in. just transfer the wires one by one.
All done, i go to turn it on and I find the thermostat is BLANK. Measuring the voltage at the green/red thermostat wires after pulling off the thermostat from the wall, i find i have no 24V anymore. At the condenser no 24V either. Whaaa? It was there before. I either blew the transformer or something else did in the 4 days since I tested before.
Upstairs in the attic I open the panel on the air handler. The transformer is in the back in the lower right. No 24V on it's output. Remove it and find that the primary coil measures open.
I buy one on ebay for $11.99
When transformer comes I swap it in. Now I have 24V power. Thermostat is working again. Outside the condenser is clicking again. A week with out cooling and a total fail. I'm right where I started. It was not the control board.
At this point I got lucky. I played with the thermostat and I find that the unit will heat, but not cool. In heat mode the condenser starts right up and heat pours out. That is the big clue. Googling heat and no cool problem I find quickly that the reversing valve is likely the issue. The reversing valve switches the direction of flow of coolant.
Reversing valve is inside the the outside unit. I have to take the top off with the fan and reach down. The reversing valve looks like this. I didn't take a real picture, this is generic picture. On top is the solenoid. When I disconnected the wires from it, the clicking stopped.
I measured the voltage at the solenoid and it was getting 24V. There was no magnetic field from the soldenoid (put a screwdriver near it and it should be attracted) and resistance was about 1.5 ohms. It should be 10-60 ohms. The solenoid part (blue in this picture, but red in my unit) comes right out by removing the nut you see on the side.
I ordered a new one for $12.75.
Trane American Standard Heat Pump Reversing Valve Solenoid Coil COL05901
After thinking about this repair I think the 24V transformer was the root cause of blowing the reversing valve solenoid. The PRIMARY of the transformer was open when it was blown, which makes no sense that I blew it swapping parts. Perhaps the 24V over voltaged the solenoid and blew it. So that makes me feel better, i replaced the bad transformer in the process.
Posted by siliconfish at 9:15 PM