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Heating & Air Conditioning

Can't figure out wiring for old Carrier outside AC

last year

last modified: last year

The thermostat looks normal, though simple and has a G, W, Y and R terminals populated but the system board has only W, R and C populated and none has wires going to the Carrier. To complicate things there's a haphazard splice in the basement where the thermostat wire is spliced and I think only 1 of the 2 24 volt leads from the Carrier connected there and some of those wires were pulled loose, the Carrier 24v lead(s) among them. I took the top off the Carrier to see how only 1 wire connecting could even be possible and the 1 of wires connects to a small circuit board then to a relay but the other wire goes across half the unit then splices with a yellow wire then goes down into the bottom of the unit and along with a 2nd yellow wire attaches to what looks like a rubber insulator then into a compressor pipe. At least that what I think I'm seeing. In the last pic you see the rubber insulator and the 2nd to last pic you can see where the blue wire is spliced with the yellow (black tape) then goes down the hole in the "ring". As you can see in the first pic the WHITE 24v wire attached to the Carrier BROWN wire and the RED 24v wire attaches to the BLUE wire. Does anyone know which wire(s) from thermostat goes to the Carrier? I;m pretty sure it was only one though that sounds impossible. I hooked up the Y to the white 24v that goes to the brown wire on the Carrier but that did NOT work. I'm afraid to do anything else without some guidance.

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Comments (13)

wdccruise
last year
What are the brand and model numbers of the (a) inside air handler and (b) outside air conditioner? All wires from the thermostat will NOT run to the outside unit. For example, the signal from the G (blower) wire is not needed by the outside unit.
mia berk
Original Author
last year
Thank you for the quick reply. Heat work fine. I have a pic of the original wires on the system control board. At the tstat w, r and g run to the system board. I'm not sure what was connected at Y on the tstat but Y is empty on the system board. There is also a splice across the basement where the 2 24v wires came from the Carrier and connected to the system and this haphazard splice got pulled apart and I cant figure out the AC setup and how the 2 leads from outside get connected. This is straight Carrier setup with everything by Carrier and installed by a major Carrier supplier/servicer. I can't get the models now but the condenser unit is model 38EC060300 made I think in the early 80s or 90s. As I understand it the condenser needs one wire going to the Common and 1 going to the Y at the tstat to tell it to turn on but shouldn't there be something attached at Y on the system board? ( there has NEVER been anything attached to Y on system brd). In the pic I'm not sure anything is connected to the blue wire on C. It appears to be cut at the splice and left unconnected. Maybe it was used to provide Common for the Carrier outside.
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mike_home
last year
I see three wired connected to the C terminal on the control board. One of them is yellow. Could someone have intentionally connect the yellow to ground so blower would not turn on? If the same Y wire is connected at the thermostat, then if you were to call for cooling the Y would be shorted to ground and probably damage the thermostat.

You should try first to get the blower working when trying to cool. It might be as simple as moving the yellow wire to the Y terminal. I suggest using a voltmeter as a troubleshooting tool.
mia berk
Original Author
last year
NO. The bundles of 18g wire going up to the tstat (2x18g + 5x18g) don't even have a yellow wire and the blue wire is cut at the splice so blue is doing nothing (at the moment). The 2 leads from the outside unit definitely were connected at the splice so my thinking is maybe 1 was connected to the Yellow (attached to C on the control brd) to provide the Common connection and the other was attached to the blue wire going to Y on the tstat. Since I don't know much about this stuff I'm hoping someone has an idea. Again, the leads to the Carrier were definitely connected at the splice. Also, the Y on the system control brd has NEVER been populated. These extra connections doing nothing and the splice really confuse things. Thank you Mike!
PRO
Austin Air Companie
last year
Since I don't know much about this stuff I'm hoping someone has an idea.

This thing belongs in a museum / the reason it's not running could be due to pressure switch trip or the commonly referred to thing > I think she just needs some freon.

Oh is that all? Yeah the bigger wallet draining problem is R22 Freon has been deemed a "how dare you" kind of gas and as such will make this relic a true recipient of an AC grave yard award.

Psst: The pressure switch is the little green thing sticking off the pipes inside the condenser with 2 yellow wires coming off of it. It's in the last picture from the first batch of pics you posted.

Another problem is the burnt wire coming off the contactor. --- I always look to the most costly thing first --- because time is mmmoney honey and people with such old equipment think these things last forever.

Oh ok let's buy another unit with a different freon... just be aware the refrigerant of the unit you buy this year is in the cusp of another freon phase down and ban.

Say What? They not only coming for your freon money, they coming for your new equipment money too.

Part 1 of a multipart series on my Youtube Channel. (Part 2c (part 3) of this refrigerant wars series is coming soon) . The first chapter of this series is just about the dirty details of how, what, why, when, where this is happening. If that interests you skim my channel "Gov Regs new freon ban?" is the icon to that clip. (each part to this series is about 30 min long) -- So you realize time is what you pay with in this realm.

I service the Katy, Texas area.
wdccruise
last year
- Control (thermostat) wiring diagrams: Carrier 38YCC Installation And Start-Up Instructions Manual page 6
- Power wiring diagram: Carrier 38YCC Installation And Start-Up Instructions Manual page 5
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Charles Ross Homes
last year
The above post by @wdccruise is what a recommendation looks like that's germane, helpful to the OP, and lacking any self promotion or ego stroking. Might be a model for some "pros" to follow.
fsq4cw
last year
I agree with Austin, this thing looks like a piece of space junk set for atmospheric re-entry. The OP might be better off with window shakers.

IMPO

SR
mia berk
Original Author
last year
last modified: last year
Actually it's worked without a problem for 31 years and till the wires got crossed (i"m pretty sure a dead short to Common) it worked perfectly. We're probably moving in a couple of years and hate to make a large expenditure at this point. I know about R22 and that fact that it shouldn't exist any more and probably will not exist in the near future but I really hate to spend thousands of dollars if this thing can be fixed by replacing a contactor or transformer or whatever. Again, this thing has never had a service problem. I used to have regular service on it but when I realized that the guys weren't even going outside to look at the unit, I cancelled them. That was 2 yrs ago.
wdccruise
last year
Ignore all the blah-blah about replacing the unit. Did you compare the wiring with the wiring information in the documents I linked earlier?
PRO
Austin Air Companie
last year
Again, this thing has never had a service problem. I used to have regular service on it but when I realized that the guys weren't even going outside to look at the unit, I cancelled them. That was 2 yrs ago.

A common rebuttal to a broken air conditioner is... but it was working just 5 min ago how could it be broken?

Your car was working just yesterday now it won't start? but it was starting just fine yesterday?

I spend all summer long fixing broken air conditioners that were working just a few hours earlier. Most of them younger than the one you show in this post. Maybe it's an electrical problem, maybe it's an electrical problem mimicking something else.

I service the Katy, Texas area.
w0lley32
last year
On the third picture of your original post, on the right of the photo, I see a brown wire going to what looks like the contactor that is corroded on an inch or so. This is usually signs of the connector overheating from a loose connection. You might want to start by shutting the power to both the indoor and outdoor units, cut the damaged section of wire and crimp a new connector onto the wire. If the existing wire is too short, you can crimp a connector to a new piece of wire of the same size and splice this new piece of wire to the old wire.
w0lley32
last year
The wire I am referring to is also shown more clearly on the left of the 4th picture, next to a yellow wire going to the left of the contactor.

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