PTT not working when engine running

[azonic75]

Having issues with ability to transmit when engine running and alternator on.
Otherwise works OK. Switch, wiring checked. A ground issue? Problem appeared out of nowhere

Kai

 

[GLPalinkas]

Radio

What kind of radio are we talking about?

Might be specific to a certain brand and someone could have a quicker solution.

 

[az_gila]

Vibration issue?

Look for loose connections in the PTT wiring

 

[Ron B.]

Can you try radio before activating alt. field?

 

[Walt]

Is your PTT wired through your Hobbs switch

 

[azonic75]

Details

Radio is a Narco 120

PTT is wired out of radio, to switch, to firewall ground

Works perfect when master is on and engine not running, when engine is running and alternator field is off it works, when alternator is on then PTT/transmit doesn't work. Receives just fine. This is a new problem. Was working perfectly up until a week ago. Thanks for ideas, NORDO flights into towered fields, while good practice using light gun signals takes a bit of the fun out of the flight!

 

[BobTurner]

For now, turn off the alternator when you need to transmit!

What is the buss voltage with the alternator on? Almost sounds like the transmitter works with 12.6 volts, but not with 13+. A very odd failure.

 

[az_gila]

Radio is a Narco 120

PTT is wired out of radio, to switch, to firewall ground

Works perfect when master is on and engine not running, when engine is running and alternator field is off it works, when alternator is on then PTT/transmit doesn't work. Receives just fine. This is a new problem. Was working perfectly up until a week ago. Thanks for ideas, NORDO flights into towered fields, while good practice using light gun signals takes a bit of the fun out of the flight!

Pull the ground connection off the firewall and make a temporary jumper you can use in the cockpit.

Make a jumper from the stick switch you can touch to ground when the engine is running.

I bet the wires are crossed somewhere.