KVT-400 Troubleshooting Guide
Troubleshooting for the AutoVent KVT-400 wind-direction curtain controller.
Screen blinks on and off without showing any error codes
The screen only shows the AutoVent logo with a black background briefly, then goes black. Several seconds later it does it again.
The wind sensor gets power from the controller / screen board. If the wind sensor shorts out, the controller and screen will restart.
Test 1
Take a picture so you know how to reconnect the wires.
- Disconnect terminal 96.
- Disconnect the rain sensor’s 3rd terminal, labeled blue.
Does the controller still reboot?
Still reboots – disconnect all terminals 96, 97, 98 & 99 and all 4 rain sensor terminals.
If it still reboots, check power supply voltage. It should be 24 vdc between terminals 30 & 31, and 3.3 v between 96 & 97.
Test 2: testing wind sensor wires
This test assumes the controller stopped rebooting when all the weather sensor wires were disconnected in Test 1.
Go up to the weather sensor junction box:
- Take a picture of the wires inside the junction box.
- Disconnect all of the 8 wires coming up from the controller.
- Make sure none of the now-loose wires are touching each other.
- Reconnect all the wires down at the controller.
Does the controller reboot with only the wire connected?
Yes – replace the wire.
Expansion box: 6th relay from the right on forever
The 6th relay stays on regardless of the output status.
- Remove the 2nd top-left screw.
If the relay turns off as the screw is loosened, leave the fastener out permanently.
Troubleshooting KVT-400 DC motor power
Check between blue & purple with a DC meter. With a motor running it should be about 24 v. Not running, it may read as high as 48 vdc.
Is 24 vac coming out of the transformer on the fat red wires?
No – go to the transformer check. Check if 120 v is going into the transformer between white and yellow.
Is 24 vac going into the rectifier?
Fans turn off whenever a curtain motor starts
The user tried to use the motor (blue & purple wires) on the KVT-400 to power a fan contactor. Bad idea, since the solid state is constantly turning the power off and on whenever a motor runs. His fan constantly cycled.
The user needs to power the fan contactors from a different power supply.
Curtain only goes open, doesn’t close (new KVT-400)
From the main screen, press the offending curtain, then press the little close button to the left of off.
If the curtain is wired correctly, the curtain will then close regardless, even if it’s at zero percent.
In this case, an inexperienced electrician was installing and wasn’t sure if the wires were connected correctly.
- It was a loose screw on the aluminum busbar.
Curtain losing position
This was a 400 ft long curtain with a ShadyLane motor. It was taking 12 amps or 18 amps depending on its mood. We had to set the amp setpoint very high and use a bigger circuit breaker. Eventually the motor got replaced and the amps were more consistent.
Wind direction but no wind speed
Use the Test program in the About screen. Scroll to the wind meter test. Jump 98 & 99 at the control to make sure the input works at the controller. Then test again, jumping 98 & 99 up at the wind sensor junction box. If the controller correctly detects the jumper in both locations, replace the wind sensor.
Variable-speed fans not running after a storm
Check the 0-10 dc voltage between 5 & 6 as circled below. Put the black tester lead on – and the red tester lead on +.
Disconnect the wires from 5 & 6.
It should be exactly as shown on the variable speed button value. 100% means 10 v, 50% is 5 vdc.
If the voltage goes to nothing as soon as the VFD is connected back to 5 & 6, then a VFD is shorted out somewhere. Disconnect the VFDs one at a time until you find the offending VFD or shorted wire that needs to be replaced.
Display not on
- Disconnect the red wire from the power input.
- Measure DC voltage between the black & red wires.
- Under 20 vdc – check the power input, or change the power supply.
- If you get 24 vdc, then the power supply is good and something is shorting out the power supply.
- The short could be from the components that use 24 vdc.
Check the 24 vdc components in their most likely sequence:
- AV430 display board (disconnect the expansion box to check, but make sure power is off to disconnect / reconnect).
- AV5 in the expansion box.
- Rain sensor.
- Humidity sensor.
Replacing the LCD
Make sure power is off.
- Remove the 4 stainless screws (likely you can leave the wires attached).
- Lift the board off.
- Remove the 4 spacers. Use pliers to keep the spacers from spinning. Gently take them off, as their front screw heads are underneath the label (and we don’t want to ruin the label).
- Gently lift the AV430 out.
- Put the new AV430 in. Be careful not to stress the screen’s yellow ribbon cable. Slide it in over the screws without ramming, or the front label will get poked out.
- Put everything back together in reverse order.
Power back up. Test the system. From the display, cycle all the relays to make sure they all work.
Set up the unit. All the parameters will have been lost, as they are stored in the AV430.
- You will need to enter the number of curtains and fans and their starting relays.
- You will need to set the direction of each curtain.
- You will need to reteach all the curtains.
Expansion not communicating
Do the blue expansion boards only read zero on their screens?
The screens show how many times per second they are hearing from the main box. Zero is a bad deal – that means it is not talking. A functioning system should read 3.8 v DC between the white & brown.
Method to check communication (process of elimination)
- Disconnect the brown & white wires (turn power off first).
- Turn power back on. With a DC voltmeter, between the brown & white terminals it should read approx. 3.8 v. A zero volt reading means it is disconnected or the screen board is bad.
If it has 3.8 v when there is no expansion, but the voltage drops near zero when the expansion is connected, the blue expansion might need to be replaced.