[keepemrunning]

Have comm err 91 and upper right red light lit. Swapped stats and problem stays with system, swapped stat shows err 91 as well

 

[keepemrunning]

I have three systems connected to tam unit or(telephone access module) would a battery failure in the tam cause an err 91?

 

[jpsmith1cm]

moved to AOP residential

 

[keepemrunning]

Checked tam 2 units are still communicating its a local stat issue any ideas?

 

[second opinion]

Checked tam 2 units are still communicating its a local stat issue any ideas?

# 91 can lead to multiple different scenarios that will need to be tested to narrow down to specific cause.

 

[keepemrunning]

Further investigation shows that the fault light on the ahc (air handler control board) blinks three times indicating two things, first is no system comm. Comm led is lit and appears to be functioning correctly. However the second indicator for fault light blinking three times is loss of the bit master time clock, this led is not lit as it should be. Verified this bm led is lit on my other units and the bm led is lit and functioning correctly. So my question at this point is can this bit master time clock be restarted or do I need a new ahc circuit board? By the way, I powered down the unit then powered up and entered the test unit mode before it detected the bm fault and everything tested normal.

 

[second opinion]

Further investigation shows that the fault light on the ahc (air handler control board) blinks three times indicating two things, first is no system comm. Comm led is lit and appears to be functioning correctly. However the second indicator for fault light blinking three times is loss of the bit master time clock, this led is not lit as it should be. Verified this bm led is lit on my other units and the bm led is lit and functioning correctly. So my question at this point is can this bit master time clock be restarted or do I need a new ahc circuit board? By the way, I powered down the unit then powered up and entered the test unit mode before it detected the bm fault and everything tested normal.

There are wiring tests that will lead to the fault. It appears to be in the control wiring.

 

[keepemrunning]

I have another 3 ton identical system, should I take the chance and swap the ahc boards on the units?

 

[keepemrunning]

Before changing anything checked outdoor unit for faults, had one flash of the fault led indicating the same two faults I spoke of before. Since the reply above stated control wire issue I disconected the two comm wires at the condenser and returned to the air handler to find the bit master time clock led is now functioning. Checked acculink stat and now it showed a code of 126 which means configuration has changed since start up. I figured this was due to the condenser being disconnected. Terminated comm wires at the condenser and returned to the air handler. No more fault lights on bm led, checked fault lights at condenser,had none, returned to acculink stat and adjusted for cooling and now unit is running. Go Figure! This would have cost me hundreds to pay for somone to chase this bug. Thanks!

 

[second opinion]

Before changing anything checked outdoor unit for faults, had one flash of the fault led indicating the same two faults I spoke of before. Since the reply above stated control wire issue I disconected the two comm wires at the condenser and returned to the air handler to find the bit master time clock led is now functioning. Checked acculink stat and now it showed a code of 126 which means configuration has changed since start up. I figured this was due to the condenser being disconnected. Terminated comm wires at the condenser and returned to the air handler. No more fault lights on bm led, checked fault lights at condenser,had none, returned to acculink stat and adjusted for cooling and now unit is running. Go Figure! This would have cost me hundreds to pay for somone to chase this bug. Thanks!

The connection was your issue. There are step by stem diagnostic charts to follow that leads you to your fault as you found.

 

[keepemrunning]

The connection was your issue. There are step by stem diagnostic charts to follow that leads you to your fault as you found.

Do you know how I can get these diagnostic charts for my systems? I have plans on keeping them for a long time it would be a great helper in troubleshooting.