Power antenna help if available! - P80

Post by **scot850** » 09 Sep 2025, 23:21

I pulled a cheap used antenna from a 00 C70 convertible. Some clown had tried to remove it and bent the antenna. It was also jammed from dirt. Normally the motor and the rest of the unit are robust. I think I have only had one bad one where the motor had failed.

I have a test kit for P80 music systems including wiring to allow testing power antennas. In this case I can get the motor to activate (I have removed the old jammed antenna mast) when turning the radio on, but it does not change the direction of the motor when the radio is turned back off. I connected up another unit thinking I had maybe forgotten the way to test it as it has been probably over a year since I last fixed one. I have an aftermarket unit easily accessible that I can use to check radio reception and operation. Connecting it up it works just fine, mast raises when radio is turned on, and lowers when turned off.

The new test unit I am trying to fix has no antenna fitted as the old one was seized. I have a new antenna but I need to be able to reverse the motor to draw the mast into the unit. There are only 3 wires:

1) A black ground wire
2) A blue and white wire I call the signal wire from the radio
3) A red/green cable that delivers constant power

The Volvo unit has the same wires, but it does have an additional woven ground wire that ground directly to the car. Should I be using this as well? I just need to be able to reverse the motor is anyone has any ideas. The unit could just be faulty, I will find one of the Volvo units I have and see if it operated the same way or not

Thanks,

Neil.

The only difference between the aftermarket unit is it does not have the little semi-transparent box mounted on the mast shaft.

bronco · Post by **bronco** » 12 Sep 2025, 03:47

If the box is semi-transparent you are all set. Just peer inside and ascertain the condition of the tiny hamster within. If the mast was bent he is probably exhausted

Post by **scot850** » 12 Sep 2025, 12:45

Nope, he is just fine and healthy, but can't find the reverse gear for some reason. It only runs when the radio is switched on and lifts the antenna if I could get it installed. Problem is when you switch the radio off, the motor should run in reverse to pull the antenna back in, but this one does not. There is a spring loaded section inside the hamster wheel with the grooves in it to raise and lower the antenna. I'm thinking that the antenna was on the way up when it jammed and for some reason is not triggering the reverse motion.

I'll look at it ne a couple of weeks when I have more time. I have good working items I can look at and see what they do. I have 2 aftermarket ones and I tried one of those as it was to hand, and it runs as it should, but it does not have that antenna signal booster and whatever else the box does.

Neil.

bronco · Post by **bronco** » 12 Sep 2025, 13:53

scot850 wrote: ↑12 Sep 2025, 12:45 Nope, he is just fine and healthy, but can't find the reverse gear for some reason. It only runs when the radio is switched on and lifts the antenna if I could get it installed. Problem is when you switch the radio off, the motor should run in reverse to pull the antenna back in, but this one does not. There is a spring loaded section inside the hamster wheel with the grooves in it to raise and lower the antenna. I'm thinking that the antenna was on the way up when it jammed and for some reason is not triggering the reverse motion.

I'll look at it ne a couple of weeks when I have more time. I have good working items I can look at and see what they do. I have 2 aftermarket ones and I tried one of those as it was to hand, and it runs as it should, but it does not have that antenna signal booster and whatever else the box does.

Neil.

Late models used a magnetic over run clutch to lower the antenna , but on early examples the hamster has to exit the wheel turn around and run in the opposite direction

Post by **scot850** » 12 Sep 2025, 16:29

Any ideas on how to get this to reverse. Antenna was from a 2000 C70 convertible.

Neil.

bronco · Post by **bronco** » 13 Sep 2025, 06:14

motor reverse function should just require a DPDT switch embedded somewhere?

Well a DPDT relay since its being triggered by a boot /shutdown command from the radio ? Where is the relay is the question

all aftermarket radios now usually have the ability to operate power antennas so i doubt the signal is brand specific.

In fact older cars usually had a rocker switch on the dash to manually run the antenna up and down when you were going through a car wash . I'm picturing something like a power window switch in my uncles 77 Grand marquis

the antenna unit itself is responsible for the "I'm all done going up or down kill the power " I can't visualize beyond that except as mechanically maybe a worm gear rack and pinion etc that maybe has fallen off the end of the rack and won't engage now? A broken tooth perhaps?

Post by **abscate** » 14 Sep 2025, 05:23

The s70 antenna has a four pin connector on it.
Pin 1 gets 12V from key y terminal 30, unstitched
Pin 4 ground
Pin 2 unused except on cars with heated third row seat
Pin 3 control signal ftom radio pin A3

The 12 volt from A3 tells antenna go up.
Absence of 12 volt ftom A3 tells antennas to go down.

Post by **scot850** » 14 Sep 2025, 08:20

Thanks for that info Abscate. That is what I thought and have it wired for on my test system. Antenna mast still does not retract when radio turned off. I still think there is a internal switch withing the rotating drive wheel that may need a physical limit stop to make it retract, but I am on the fence on that. When you separate the 2 halves of the drive wheel it has a weird shaped spring and a rocker piece internally. It may not have any bearing on the operation. I would have thought the unit would time out when driving in either direction.

I will test another unit when I get back in a couple of weeks to compare.

Neil.

Post by **abscate** » 14 Sep 2025, 08:29

If I were designing this I would put a double throw relay in which shunts positive voltage to the motor when triggered by a3, the Norma;ly closes to put B- to motor to retract when A3 goes to 0.

The limiting stitches have to be in the motor case and just break voltage to the motor in either case. They mechanically reset on traction. I’ll guess antenna stuck problems are probably mostly caused by these faulting.

Post by **scot850** » 28 Sep 2025, 12:48

So final note. Looks like there is an issue with the control unit. When I connect another unit to the antenna it works as it should in terms of raising and lowering when you turn the radio on or off. It will only raise with the units own control unit.

However, there is a 2nd issue and not sure the cause of this. The (yes god forbid!) URO mast (all I could find in Canada), is that it will only drop to about the height of the collapsed antenna length and not go any further inward than that. Also the grounding collar will not fit in between the outer shaft and the mast.

I'm thinking the issue could be there may be a different control unit and timer for lowering and raising the antenna. It does seem to raise ok, but cuts out before pulling all the way in. I think I will waste no more time on this and keep the unit for parts.

Neil.