Home A/C problem

[TilliamWe]

Gentlemen, I am the proud owner of a 1977 Chrysler Airtemp electric furnace, and an unknown a/c unit out side the house, but it's old too. Bought the house with these components in Aug of 2004. One time last year, the A/C unit outside did not shut off, for many hours after the furnace inside did. So I turned off the breaker, and viola' it functioned fine. Well, last night I turned th A/C for the first time. Blew nice cold air, and when the thermostat reached the right temp, the furnace fan shut off, but the A/C unit outside kept running. I shut off the whole system at the thermostat, kept running. Went to the circuit breaker box, and turned the a/c breaker off, and it stopped. But as soon as I turn the breaker back on, it starts running. HVAC guy is coming tomorrow.<br />So, what is he gonna tell me???

 

[K Hultgre]

Re: Home A/C problem

Bad wiring, Bad T-stat, Bad Relay (furnace or A/C).<br />Just a guess. Without knowing if the signal line for the A/C is on or off its tough to guess.

 

[TilliamWe]

Re: Home A/C problem

Without knowing if the signal line for the A/C is on or off its tough to guess.

What does that mean? Is that the first thing the guy has to figure out?

 

[dolluper]

Re: Home A/C problem

Check this site for understanding stat wiring with AC note sections Left side page close to bottom<br /> http://home.howstuffworks.com/home-thermostat3.htm

 

[TilliamWe]

Re: Home A/C problem

dolluper, thanks for the link. The thermostat isn't going to be the problem, but I am in the process of reading how the a/c works & the wiring to see if I can have an idea of what to expect tomorrow.

 

[Baldguy]

Re: Home A/C problem

There may be a "signal" line between the blower in the furnace and the A/C unit outside so that the A/C unit knows when to turn on and off. A guess would be that the line "wire" is shorted or disconnected somehow. Perhaps corroded to the point where it doesn't make a complete connection any longer....thus the reason why the breaker turns it off and the blower going off does not.

 

[TilliamWe]

Re: Home A/C problem

I wondered how the thing outside knew when to shut off.<br />So Baldy & Kevin, that's gonna have to be the first thing he checks

 

[D Grass]

Re: Home A/C problem

There is a contactor in the A/C unit that has a coil which is energized by a signal from the thermostat. My guess is either the thermostat is bad, giving voltage to the contactor coil when it's not supposed to, or the high voltage contacts on the contactor itself have stuck closed. This can happen as the contacts wear out the voltage drop across the contacts becomes too high causing them to "weld" themselves together.

 

[TilliamWe]

Re: Home A/C problem

D Grass, well if wearing out can be involved then this thing has to be guilty of that! As I said the furnace was installed in 1977 (3 years before my wife was born!), and I never even knew Chrysler made furnaces. And by it's looks, the A/C unit was installed the same day the furnace was!

 

[D Grass]

Re: Home A/C problem

Just another note. As on January 6th, 2006. 10 seer A/C units will no longer be produced. The minimum Seer rating allowed by the government will be 13 seer. To make a long story short I believe it will be a lot cheaper to replace your A/C this year as opposed to next year. Just wanted to let you know this before you stick money into a 20 year old unit.

 

[TilliamWe]

Re: Home A/C problem

Not going to have much of a choice regarding replacement. I am not going to replace an A/C unit that still operates, ans blows nice cold air. And with child #1 on the way, and a wife who can't stop spending money, I haven't the coin to go replacing entire systems. But thanks for the heads up!

 

[Ben Konopacky]

Re: Home A/C problem

I second the motion to D GRASS on a contactor that has burnt (welded) contacts. Q is that compressor mounted (hung) from the top ?if so its an OLD chrysler unit .

 

[cajun555]

Re: Home A/C problem

Turn on the A/C, then shut off power to the furnace(air handler). If outside unit shuts off then most likley a t-stat or wire problem but I doubt a wire problem unless someones messed with it. You normally only have one transformer and its on the furnace. If unit outside it has a stuck contactor. About a 15.00 item. <br /><br />Forgot to ask, I assume the t-stat controlls the heat as well. If the heat worked ok then that rules out the cover interfering with internal controls in t-stat.

 

[SS MAYFLOAT]

Re: Home A/C problem

TW, On your condenser unit (outside unit) you should have your regular line voltage wiring and your thermostat wiring for the control of the cond unit. Shut off the power to the whole system.<br /><br />Remove the cover of the cond unit to the electric controls. Now follow the wires that come from the compressor back to the contactor/relay. On that contactor/relay, there should be line voltage wires going in with wires then going out to the compressor. Then there should be another set of wires that should be smaller. These are the "signal" or control wires. Pull off one of the small control (low voltage) wires from the spade terminal of the conatactor. Make sure the wire does not touch anything. Go turn the power on and reset your tstat to call for cooling. If the condenser unit runs, then your contactor/relay is stuck in the closed position. These are easily changed and are inexpensive.<br /><br />Do you have a volt/ohm meter? If you do, troublshooting your problem would be much easier. Then the second question is, do you know how to use it? Let us know, and we can go further is the above doesn't prove to be the contactor/relay.<br /><br />Good luck and make sure you shut off the power when doing any electrical work.

 

[TilliamWe]

Re: Home A/C problem

Ok, update & a continuation.<br /><br />I was not able to be at home when the fellow came (1.75 hours later than the latest time window quoted to me yesterday when making the appointment), of course! <br />And, of course, when the guy turned the breaker to the A/C unit back on, it did not start up, like it had several times before. <br />So, he "checked" the things on the furnace that he replaced this winter (sequencers), they were fine. Wife says he went outside to the A/C unit, but she did not know what, if anything he did. He spent 45 min to 1 hour at the house.<br />He then told my wife that it could be any one of 4 things, and that he couldn't tell which it was unless it was acting up while he was there. He stated that the cheapest problem would cost $300 to fix and that if he did all four it would be $1000. So his official instructions to my wife were, "when it does it again, let it run (after the furnace shuts off) call us, and I'll come back out again & diagnose it." "Here's my bill for $89 for the 'service call', please give me a check". <br />She paid him, then left me two badly worded voice mails, that I could not return for 2 hours.<br />I, of course, called the company, (after explaining to my wife why I was very angry with her) and spoke w/the Secretary. I asked that a written estimate for those "four things" be given to me. I also explained that I didn;t appreciate that my wife had to wait an extra 1.75 hours and that $89 for 45 min work was way too much. She's checking into it, but of course the tech was done for the day (at 3:15pm! nice), so she couldn't tell me much.<br />I was afraid this would happen, and that is why I asked for your insights.

 

[TilliamWe]

Re: Home A/C problem

cajun, with the thermostat in the "Off" position (it is a digital thermostat) the furnace is off, but the A/C unit runs. The way I stopped the A/C unit was to turn off the circuit breaker in the box. But when I turned the breaker back on, the A/C started back up. It did this after 1 minute, after 2 hours, and after one day, but not after two days when the tech was there.<br />Furnace worked fine this winter after I had to "sequencers" replaced. It turned on one night, blew air, but wouldn't blow hot air. The A/C blew cold air the other night that I turned it on.<br />SS:<br />

Do you have a volt/ohm meter? If you do, troublshooting your problem would be much easier. Then the second question is, do you know how to use it? Let us know, and we can go further is the above doesn't prove to be the contactor/relay.

1)no volt/ohm meter<br />2) do not know how to use it, that's why I asked basic questions here, and called an "expert"<br />3) at $89/.75 hr, I think I can afford to take an electrical engineering class at Case Western Reserve University and tell Arnold & Sons in Peoria, IL to go **** themsleves!

 

[SS MAYFLOAT]

Re: Home A/C problem

Intermittent problems is the hardest thing to figure out. I had a deep fryer in a resturant that took me 3 weeks to find out what was wrong. When this happens, it sure makes a factory trained person feel stupid at times. So I can relate to the tech that checked your unit out.<br /><br />Always tell them you want the old parts. And since you don't have a meter or knowledge, it might be best to keep it that way. Most of the time when a DIY person attempts repairing things, it takes longer for the tech to figure out what the homeowner did plus finding the problem.<br /><br />Good Luck.....Can you let us know what the 4 possiblilites were? Thanks....SS

 

[cajun555]

Re: Home A/C problem

tilliam, I know where your comming from. I do refrigeration work and erratic problems are the worst problems. Its like when you take your car to the shop because of a noise. You get to the shop and no noise.<br /><br />Normally in cases like what you have I would'nt have charged you, but would have given the customer my cell and told him to call me when the problem occurs again and he would be next on my list.<br /><br />The digital t-stat may be the problem. Some people swear by them but I've had 2 in my house and both times they screwed up in the heat mode. I'm back to a plain jane old mercury T-stat. <br /><br />If it does it again kill power to furnace. Normally, the furnace power is the controlling power(24 volts) to outside unit. If unit outside still continues to run give the thing a swift kick or jar the unit. If it stops running I would almost bet a contactor sticking.<br /><br />Good luck

 

[TilliamWe]

Re: Home A/C problem

If unit outside still continues to run give the thing a swift kick or jar the unit.

Gee, I can't believe you said that! I usually do stuff like that but was very afraid to do it! Plus as old as it is, i was worried it would fall to pieces like stuff in the movies!<br /><br />Another update: talk about intermittent:<br />Started the whole system up last night, it blew cold air for about 3 hours, reached the thermostat temp, and the furnace quit. But the A/C unit outside kept running. I was not surprised! I called the answering service & left a nasty message for the tech, that i am sure the lady will not deliver. Shame on me. I decided to let the damn thing run. I turned the thermostat down lower so it would at least blow cold air, which it did. I went to bed. I got up at 4:30am, and the furnace was off, AND so was the A/C unit!<br />So, I just left it that way. I told my wife to see if it stays on all day today. But I think I'll just use it "as is", at least until it quits working totally. <br />Can't wait to see if I get that written list of possible problems & repair costs!<br />Thanks guys

 

[dolluper]

Re: Home A/C problem

It might be a good time to learn how to use multimeters if not in this case but in the future like testing on a boat or car much safer than AC voltage in house circuts<br /> http://64.233.167.104/search?q=cach...ng_a_volt_ohmmeter.pdf+using+multimeter&hl=en <br />Do a search on "Using Multimeters" lots of info out there<br /> http://users.pandora.be/educypedia/electronics/multimeter.htm <br />This site has lots of info