Crematorium managers say the lorries are disturbing services
Giant lorries heading towards a town's main industrial plants are being directed by satellite navigation to the local crematorium instead.
Crematorium owners say the vehicles are disrupting services and damaging the grounds as they attempt to turn around.
A roundabout was built serving the site in Llanelli's Penprys Road, but some maps have not been updated.
Carmarthenshire council said although it had provided additional signs, the problem continued.
Crematorium director Marjory Joplin said this week alone they had dealt with 12 HGVs.
"Some of these lorries are absolutely huge," she said.
"They try to come in to turn around as the lane gets very narrow just up the road.
"When they are trying to reverse and turn around they have got all the bleepers on and the reversing lights and the noise is incredible.
"If there is a service it's the last thing you need - it can be very distressing."
She said damage had become so bad they had taken to locking the gates at weekends.
"There is a pedestrian gate but some people visiting the memorials are elderly and can't walk very far, so it is distressing for them.
"We are are our wits end - I just don't know what we can do."
She said many of the lorries were destined for car parts plants such as Camford and Calsonic and should be turning off at the next roundabout at Dafen.
"It is not the drivers from these companies but their deliveries - often the drivers do not speak English which makes it more difficult," added Mrs Joplin.
Carmarthenshire council's traffic operations manager John McEvoy acknowledged there was a problem.
"Signage has been provided to send heavy vehicles to the Calsonic factory, for example," he said.
"However, the problem still persists because vehicles are turning right mistakenly believing it will take them to Lletty Road and the major factories there."
"To overcome the problem with sat nav, in addition to the signs to deter heavy vehicles from turning right, the traffic service will make an application to the assembly to put new signs in place that will deter vehicles from turning right because of sat nav."