Carrier heatpump, when in AC the blower is not turning off

metalmover

I have a Carrier Tech2000 heat-pump for my basement. Air-handler is a model FK4BNFoo3oooAAA. Control board CESO130007-00, variable speed ECM controlled 1/2hp 220v motor model 5SME39HL0058. Manufacture date was in 1994. The house was built in the mid 70's so this was an add on unit.
When the thermostat is in AC the blower in the air handler will not cycle off,it continues to run. I've disconnected the G wire at the circuit board and it still runs. when I switch to off on the thermostat the fan shuts off after several minutes. The system cycles normally in heat mode.
This problem has been around for I know several years, may have been that way when I bought the house 6 years ago. I rarely need AC downstairs as half of the room is underground. I've finally decided to try and take care of it but this whole ECM thing has me and my HVAC buddies a bit puzzled. Since there are no relays on the control board (which was where my online trouble-shooting was going) is the problem in the ECM module on the back of the motor? I don't see any relays there either. Can it be repaired on a component level? (I know how to solder) or do I need to replace the whole module?
I also have not been able to cross my air-handler model # over exactly, one number or one letter off. Hope it's not some odd-ball with no replacement parts.
Your help will be much appreciated!!
Thanks for reading this.
Bob

beenthere

Reconnect the wire to G, and disconnect the wire on Y, and see if it stops then. Could be a short in the thermostat wire, or a problem in the thermostat.

metalmover

Thanks for your reply beenthere!
I'm a bit confused though, I thought that by disconnecting the G wire at the circuit-board on the air-handler I thought I was eliminating the thermostat.
Do you mean disconnect the Y wire at the board?
Thanks
Bob

JJboy

disconnecting the G wire only blower motor should stop......disconnecting the Y wire AC should stop running


Disconnect all wires at thermostat
Connect R-G - Blower on
Connect R-Y-G AC, Blower on.....cold mode

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

Master of Cold

There is a heater/fan board in the unit. Fan signal comes from that board to the motor. Btw..that may be the last Tech 2000 running...

metalmover

[JJboy;732340disconnecting the G wire only blower motor should stop......disconnecting the Y wire AC should stop running


Disconnect all wires at thermostat
Connect R-G - Blower on
Connect R-Y-G AC, Blower on.....cold mode[/quote

I put the motor and blower back together, hooked up all the wires. The Ac comes on but the blower still does not cycle off when the temp is satisfied, same way it was before I took it apart..
NOW...At the circuit board I can disconnect the G wire and the AC will come on, blower and compressor. while the unit is on I can disconnect Y & G wire and the compressor and blower continues to run. My meter shows 24v on both wires that are disconnected.

Doc Holliday

R terminal (red wire usually) disconnects stat. Be honest, you don't have any a/c buddies.

metalmover

LOL, I really didn't want to hear that. Guess it runs so little it has lasted a while.
Compressor is still going but I don't need all this variable speed crap for a 1000sq ft basement. It's like a wind tunnel when the fan is on high! Ever tried to retro fit one to a single speed?
Thanks,
bob

metalmover

I work at a large theme park in rides maintenance, I'm a journeyman machinist by trade but I'm out in the park chasing ride problems more that I run a machine. I'm also in charge of design, prototype and installing special projects, usually pneumatic systems. My HVAC buddies at the park are not familiar with this vintage variable speed control unit. My goal here was to verify that I need a new ECM.
Wat I'm not sure about here is if the board does not need the 24v input to turn on the fan then where is it coming from? With no relays to stick closed in the ECM the computer board in the motor module must be shorted. Would that be a correct assumption?
Thanks for all the help so far!!

JJboy

Post some images.


Is this your control board? You can test these diodes....this control board is only a distribution board.....I don't think your problem is here

Attached Thumbnails

 

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

Doc Holliday

The control power is in the air handler, not in the stat unless it comes from the air handler transformer.

I can't believe it but my image made it to google somehow. Master might know something about these. This is an old Ruud or Rheem 7.5 ton 460 volt belt driven air handler, one I've worked on a few times.

See that little black box looking thing on the floor of the wheel assembly door on the right? Not the heat strip door but where the blower wheel is. All the wires are a mess and hanging all over the place. That is not my work, btw. I was there changing the shaft, bearings, belt and wheel and that is all.

Anyways, that is a transformer. It takes 460 volts and "transforms" it to 24 volts to be sent to the thermostat. All a stat is is a switch that closes and opens.

You'll have a transformer in your air handler, that is where your voltage is coming from. You don't need a stat to operate your system.

Doc Holliday

oops, I left the image off.

77%

Master of Cold

Yea..that's a hunk o junk.

beenthere

At the furnace. Disconnect the wire from the Y terminal. have all other wires connected where they belong. turn power on and see if the fan still runs with the system in cool mode, and the thermostat not calling for cooling.

A triac based thermostat can bleed enough current through the wire connected to the Y terminal that the fan will run.

Master of Cold

If you can post a pic of what control board you have it would make it much easier. You are saying "ecm" motor. But if this is a variable speed blower there is not a problem, just a fan delay timer that can be adjusted..