Carrier model 58mvp

rmahoney

I'm trying to troubleshoot a Carrier 58MVP furnace that the main blower isn't working.This is a variable speed motor how can I determine if I have a bad motor or no output from the cpu. I've never seen one of these before.

Tom_32

Not Easy

There is no easy way to troubleshoot this furnace. The Carrier uses the GE ICM variable speed motor like almost all other manufacturers but the control boards are different. It also depends on which version of the ICM you have. Your local Carrier parts distributor has a tool that will troubleshoot the motor. There also is a diagnostic procedure using a voltmeter, but it is not easy. The Carrier manual has about 20 pages devoted just to troubleshooting the motor. Either way, you'll have to talk to your local Carrier rep.

Matt Undy

I can only make general statments without seeing a schematic, but you should be able to check the motor with an ohm meter (unless it has some sort of tachometer in it in which case you can check the windings but may or may not be able to check the tachometer depending on its type). Is the motor driver a seperate circuit or part of one control board for the whole furnace (so the power semiconductors that have a tendency to fail may be replaced without replacing the whole control board). If the motor windings aren't open and the controler is getting power and control signals then its the controler. High power semiconductors aren't known for reliability so the controler is a likely culprit.(if its a standard inductrial motor and controler enough of a schematic to troubleshoot should be available).

Matt

Matt

Dale

Book

For this you need a book. The motor part of the motor seldom goes bad unless it's a big lightning hit. The motor controller part of the motor plugs into the end of the motor and should be inspected for burns or lightning hit marks. If theres a large plug into the motor turn the blower wheel by hand after jumping any 2 of the pins. the motor should turn freely.

pj_2

testing ge ECM

Ge has a diagnostic tool called TECMate* sells for about 60 bucks or
you can jump out pins #1&3 to the common side of the 24v trans
and pins # 12 & 15 to the hot side of the 24v transformer
you should get 50% of the cooling speed

pj_2

testing ge ECM

Ge has a diagnostic tool called TECMate* sells for about 60 bucks or
you can jump out pins #1&3 to the common side of the 24v trans
and pins # 12 & 15 to the hot side of the 24v transformer
you should get 50% of the cooling speed

When in doubt jump it out. just kidding
Now that I opened my big mouth
I hope you're a technician

Unknown

It is difficult to

troubleshoot the GE ECM motor with out the GE TECMATEXL Service Tool which is available for 49.97 + shipping and handling from www.GEindustrial.com/dealer.

You can however isolate the problem from the control module at least.Before replacing the control module check the mechanical integrity of the motor itself by rotating the shaft by hand. This is done by

1. Remove the control module by locating and removing the two 1/4" bolts from the back of the control. The control module is now free of mechancial attachment to the motor module endshield, but is still connected by a plug and three wires inside the control.

2. Carefully rotate the control to get at the plug at the control end of the wires. With your thumb and forefinger reach the latch holding the plug to the control and release it by squeezing the latch tab and the opposite side of the connector plug and gently pulling the plug out of the connector socket. Don't pull on the wires grip the plug only. This will detach the module from the motor.

3. With an ohmeter measure the resistance from each connector pin (in the motor plug just removed)to the motor wiring shield. It should be 100,000 ohms. (This will determine that the motor winding is properly insulated and not damaged.

4. Rotate the motor shaft to see if it is rubbing and or mechanically defective (hard to turn) If you get resistance up and down as you rotate the shaft that is an indication that the rotor is aligning with the stator and is normal with this design.

5. If any motor connector pin fails the ohms test and the shaft does not rotate easily, then both motor and control is defective and must be replaced.

If the motor module passes this test but failed the TECmate test (tough to know if you do not have the tester)then the module only needs replaced.

Another thing does the motor operate with different thermostat calls heating, AC, continous if it runs in all but one speed look to the control module if it will not run at all the motor is suspect.

Make sure all the wires from the control board to the motor are making contact (ohm them out for continuity) I have had a couple of cases of bad connectors.

You really need the tester!!! I hope you are a technicain and not a homeowner because this is really a job for a pro.