I put a rebuilt antenna in my 86, and an aftermarket stereo. The antenna will go up when the car is started but then goes back down it wont stay uo.
Peggy

 

Is it an aftermarket antenna with only two wires and a ground wire for a total of 3 wires? Or is it a direct replacement of the original one?

If it's an aftermarket like a universal one, just eliminate the factory antenna relay out of the picture. They just need a raw signal from the radio. The relay only messes things up. The Pink wire at the antenna relay located in the storage compartment is hot at all times. This one keep the antenna down. The Orange wire at the antenna relay is only hot when the radio is on. This raises the antenna. When the radio is off, the Orange wire looses voltage and the antenna comes down and stays down by the always hot Pink wire. Use a multi-meter to make sure that this is happening in these two wires. Just snip the relay off and leave it where it is with about 3 inches of wire incase you want it back in the future, and connect the antenna directly to the Orange and Pink wires that fed the relay. The ground wire can go with the black ground wire of the antenna relay connector.

If it's a direct factory replacement antenna, check to make sure that the Pink wire that feeds the Antenna Relay in the gets battery voltage and keeps battery voltage as long as the radio is on. This is what keep the antenna up.