Reports that a radar dome in Norfolk is causing electrical problems with cars are being investigated by the Ministry of Defence (MoD).
Motorists say their engines and lights have cut out, and their speedometer dials swing up to 150mph as they drive past the Trimingham radar unit.
Neil Crayford, who runs a garage near the dome, said in the past two months, 30 car owners had reported problems.
On Monday, an MoD spokeswoman said the claims were being investigated.
Mr Crayford said one night his own car's headlights and dashboard cut out for a few seconds as he drove past the dome in convoy with a colleague - who suffered the same fate.
The former RAF radar operator said: "Something must have changed - either the frequency or output - for this to happen.
"I lodged an official complaint with the MoD two weeks ago, but incidents are still happening. We get about five a week, and had three more on Friday."
An MoD spokeswoman said: "We are aware of claims that the remote radar head may be interfering with car immobilisers and we are investigating.
"There are other users outside the military that operate on the same frequency as the radar, but there is a possibility we could be causing some problems with cars."