Although I've checked the archives for antenna issues, I've not found one that matches the one I'm experiencing.

The power antenna was intermittent, at best. Sometimes it would go up (and down) just fine, other times only part way (in each direction). The mast and collar are fine. I've bench tested the unit out of the car with the same results applying the harness connecting the antenna to the car's wiring. When I bypassed the electronic control module and applied 12VDC DIRECTLY to the leads of the motor, the antenna would raise and lower fine, consistently. So I deduced that there was something wrong with the electronic control module. Maybe it was too current sensitive. [I assume that, since there are no limit switches on this mechanism, the only way the circuit would know that the antenna was either all the way up or down was by an increase in the locked rotor current of the antenna motor.]

So I ordered this over-priced, un-returnable, special order module from Volvo and guess what--no change. Same symptoms. So I thought, maybe there IS something wrong with the mast or collar. [There is no tail piece broken off in the gear housing. I checked.] I bought new mast. Still no change.

By now I've practically spent as much to fix this as a new antenna and am still reluctant to because I can see the mechanism can pull the antenna up or down if I bypass the module. I feel by replacing the whole darn thing, I'm throwing away a "perfectly" good antenna.

Anyone have experience in this kind of antenna situation?

You are cleaning and lubing more often with all the salty crap on the road in the winter? My '99 S70 tells me when lube is overdue by sticking partway down.

My 98 S70's antenna often will not go all the way up. I turn off
the radio and on the 2nd try it always works. It always goes down
all the way, though.

I have had two antenna failures on my old BMW and just replaced the whole antenna both times. I tried to replace the shaft once and never could get that to work. These aren't two difficult to replace yourself and you can probably find an aftermarket antenna that will work fine.