I installed a Goodman GMV95 two speed gas furnace with ECM fan motor last fall. It functioned perfectly last winter, cutting my natural gas bill almost in half. When I installed the unit, I set it for 720 cfm (my ductwork is a little small for 95% efficient equipment) and verified the airflow by clocking the gas meter and checking temperature rise. My static pressure was under .3 inches on high fire.
Two months ago I started it up and notice a lot of blower noise and low temperature rise. The static was running 0.7", and I used a Tru-flow plate to find the airflow was a little over 1000 cfm. The green LED that is supposed to flash airflow wouldn't work, it just flickered dimly. Otherwise, the unit is running fine.
So far:
1. Checked all the ductwork, the electrical ground, thermostat connections, cleaned HTX.
2. Replaced control board - nothing. I switched to a spun glass filter to get the static down to 0.5" - in the range that Goodman requires when firing.
3. Called Goodman tech support.
4. Cleaned all connections, checked for moisture.
5. Called tech support again, changed the endbell (control module) on the ECM motor.
The static is still at 0.5", and I think the airflow is still high. The green LED is working now, and flashes 7 times (700 cfm). I will bring the Tru-flow plate home next week to check airflow, but I may repeat the temp. rise / meter clock to verify the airflow this weekend.
Has anyone had an ECM motor that just doesn't seem to blow the correct amount of air for what it's programed?:confused:
P.S. - I don't have an AC coil on the unit yet.

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Go to ECM service guide and download. Enjoy

The tech guide is very good - now I know what else to check!

:) Hey thanks HVAC1000. When I replaced the endbell, the instructions told me to do the phase to case check (less than 100k ohms), but it didn't say anything about the phase to phase check (less than 20ohms and equal). I'm going to try that when I pull the blower again. Thanks for the info!

You need a score card to keep track of the game if you know what I mean. At the university where I teach sometimes we have fun with the variable speed DC motors. We write our own programs and burn a chip just to see what we can make the do. Lucky for us the equipment is all for free from the manufactures cause we do mess one up from time to time.

here is something for you about your equipment.

Subject: ECM Motor Not Ramping Properly on Goodman® Brand 80% and 90% Variable Speed Gas Furnaces
( From HVAC1000). Just thought you would find this interesting )

There have been reports that the Goodman® brand 80% (GMV8*) and 90% (GMV9*, GCV9*) variable speed ECM™ motors are not ramping up and down. The ECM™ motor is operating at 100% fan speed on start up and immediately shutting down when the thermostat cycles the unit off.

We found that the ECM™ motors with a date code range (0406 through 0410) had a programming error not allowing the motor to ramp properly.

The following are instructions to correct this condition when using the variable speed gas furnace by itself and when using the furnace with a heat pump in a dual fuel application. The ECM™ motor assembly does not need to be replaced.

(1) Gas Furnace Only.

Install a jumper wire between the "O" and "Y" terminal on the control board. The "Y" terminal now received the "O" terminal's programming instructions, which is the same as "Y". The ramping profile is now activated and will ramp up and down properly.

Note: In the future, if the gas furnace circuit board is replaced before the ECM™ end bell is replaced, the jumper will need to be installed on the new circuit board to maintain the ramping profile.

(2) Gas Furnace with heat pump (dual fuel application).

First, the "O" wire from the thermostat and the "O" wire from the heat pump should be connected together with a wire nut. DO NOTconnect these two "O" wires to the gas furnace circuit board.

Next, install a jumper wire between the "O" and "Y" terminal on the gas furnace circuit board. The "Y" terminal now receives the "O" terminal's programming instructions, which is the same as "Y". The ramping profile is now activated and will ramp up and down properly.

Note: In the future, if the gas furnace circuit board is replaced before the ECM™ end bell is replaced, the jumper will need to be installed on the new gas furnace circuit board to maintain the ramping profile.


Goodman Buletin #S-210

Hope you find this useful also.

BTW if you ever have some time to burn visit a friend of mines web site. Has been making these for over 20 years with great success. I have sold many of these variable speed controllers over the years. My customers just thought they were as great for comfort cooling and a draft free heating experience. Here is his site. He only deals wholesale to the trade.

FanHandler.com