repair help for install problem

we have just installed a radio in our ambulance, this radio constantly squelches. it does hit the repeater when keyed, but will return to just squelch after all transmissions or when recieving. this radio has the older automatic squelch built in. we have checked all our wires . we have even replaced the radio with a different one and it still does the same thing. we have called a radio repair shop, they are having trouble figuring something out too. does anyone out there have an idea. this is really annoying while running calls in the truck.:confused:

Knowing what radio you have would help just a bit. :rolleyes: