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Power antenna motor repair/restoration

Started by Cadman-iac, September 25, 2021, 08:50:17 PM

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Cadman-iac

  I wanted to document the repair of the power antenna motor for my car.
I thought about it after another member mentioned a problem with their antenna motor, and I thought it might be helpful to anyone who has the desire to try this but might not know how or what to expect.
So I'll go step by step as I disassemble, clean, repair, and reassemble mine and post pictures of the process.
I hope this may prove useful to someone with an antenna motor problem.
 
This motor was working, but it looks horrible, and the wires are very brittle, in fact one broke off at the entry point to the motor as I was testing it.
I have never worked on this type of electric antenna before, although the motor portion is very typical of any small 12v motor.
The first step was to remove it from the rest of the unit, which in this case was just the removal of the two nuts that hold it in place.
  Once free of the mast and cable housing you can see the "coupler" that connects the motor shaft to the cable drive. I was surprised to see that it actually looks like a miniature version of the one GM uses on the power seat units on the 60's and 70's cars.
  There is also a large "O" ring that seals the end of the motor housing to the cable drive housing, that prevents water and dirt from entering.
  The next step is to remove the two nuts that hold the motor together. The half of the motor housing that the shaft goes through can then be lifted off the motor, but you may need to pry it a little with a thin screwdriver between the two halves to get it to work loose. As you lift it up, the shaft/ armature remains in the lower half.
This particular motor has the brushes mounted on a thin plate that is held in place with two more nuts further down on the bolts that go through the motor.
These take a 1/4" deep socket to remove, and once you do, the brush plate can be raised up over the shaft, but be careful as there's a single wire that is connected to the field windings. It's just long enough to allow the plate to go over the shaft. You will have to press the brushes in away from the commutator in order for it to clear the little shield that sits on the shaft. That shield is there as a backstop for the spacers and thrust washer for the shaft.
Also there's a spacer under each side of the plate that slide over the bolts. These keep the plate and brushes aligned with the commutator on the armature. They can then be removed and the bolts pulled out from the opposite end.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Moody

Nice! I'll be doing the same thing for my antenna. Good to see how you approach this.
Dave
Moody

Cadman-iac

#2
  Once the plate is out of the way, the armature can be removed. Be very careful when you pull it out, as there's a very small ball bearing that it pivots on, and below that is a small washer the same diameter as the shaft that the ball bearing rides on. If you lose one of these, you probably won't be able to find another one.
These are shown in the first picture.

  As you can see, this motor is very rusted on the outside, and there's evidence that water had gotten inside as well. So getting the field windings out will be difficult.
Before trying to pull the windings out of the housing, take the brush plate off. To do that, you will need to use a soldering iron or gun to melt the solder where one brush and the field winding are connected.
The second picture shows the field winding and brush after being disconnected.
  (On this motor the wire coming from the winding to the brush was run through the head of the little cotter key, I'm guessing to keep it from flexing or making contact with something. I don't know if this was commonly done or not, but I'll copy it when I reassemble it.)
There are also springs behind the brushes which will come out after the plate is lifted off the armature and the brushes are released, so be careful that they don't fall out.
There's also two ways to get the brushes to retract away from the shaft, I chose to just press them against the springs, but you can remove the tiny brass cotter keys on the brush holders that keep the springs in place,  however if you break one, finding a replacement may be difficult.

   After the plate is disconnected and the shaft is removed along with the bearing and washer, then you can pull the field windings out of the housing. Because of the rust on mine, the windings wouldn't budge. So I placed the housing with the windings down on my vice with the opening just wide enough for the windings to fit inside and the lip of the housing resting on the top of the vice.
Picture 3 shows this procedure.

To get the winding to move,  I used a small diameter punch and inserted it through the bolt holes, resting on the edge of the winding, and tapping it with a small hammer. Alternate from one side to the other to get it to move out of the housing. Be careful not to hit it too hard or it's possible to distort the winding core. In the third picture the winding is almost all the way out. When you get close to this point, take the housing and try to pull it out by hand. It should come loose. If not, resume tapping it with the hammer and punch,  being careful that the winding doesn't  become damaged by falling on the floor.
  The fourth picture is after I got the winding out of the housing. You can see the rust that held it tight. This will have to be removed before reassembly.

Also notice that the wires go from the top of the winding down along each side and through the grommets in the bottom housing.
The fifth picture shows the punch through the bolt hole to tap the winding with.

  So after disassembly, I had to cover the shaft bushings to prevent blast media from getting in them. To do that, I used a couple of cap plugs that are just slightly bigger than the opening around each bushing. I had to use a thin screwdriver to pry them the rest of the way in. Pictures 6 and 7 show what I used and how they fit into the housings. I also had to plug the other side of the top housing bushing where the shaft sticks out. I  used a vacuum cap to plug the hole with. This is seen in the 8th picture.
Once the bushings were protected, I blasted both housings to remove the rust and old paint that was still on it. Then I used compressed air to clean out any remaining blast media so they could be painted. The last picture shows them after blasting and just before I painted them.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

Quote from: Moody on September 25, 2021, 09:08:04 PM
Nice! I'll be doing the same thing for my antenna. Good to see how you approach this.
Dave
Good luck with yours, it's well worth trying yourself. You can save a lot of money this way.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

#4
   I suppose I should have given a little information about how these work. To accomplish the reversible feature of these motors, there are two wires that enter the motor, each one going to a separate coiled winding on opposite sides of the motor.
When you energize one, the current flows through one coil winding, through the first brush to the commutator on the armature, through the armature and back to the opposite side of the commutator and through the other brush to ground. The resulting magnetic field causes the armature to spin in opposite directions because of the direction each coil is wound.
To reverse the motors rotation, the power goes through the other wire and coiled winding.
They both end up at the first brush, and go through the armature to the other brush then to ground. It's how each coil is wound that creates opposing magnetic fields, causing the motor to run in opposite directions.
  There is a "safety feature" installed on the brush plate to try to prevent damage to the motor if it is stuck or dragging and power is still being applied. It's a built in breaker basically. It looks very similar to the ones that are used in headlight switches. There is a set of contacts, one side connected to the ground point, and the other attached to a bi-metal strip that when too much current draw goes through it,  will heat up and flex, breaking the power flow temporarily.
However it's still possible for damage to occur if the motor is stuck or dragging and the issue isn't fixed, eventually it will cause something else to fail. I have seen things like a burned through wire on one of the windings, or a connection between the winding and brush, or even one of the connections on the armature can come loose from overheating.
So if your motor is inoperative in one or both directions, these would be things you should look for.
  There's no guarantee that a motor is repairable, but there's a chance it may be. These are just some things that you need to look for.
   This particular motor has fairly thick wire used for the windings, but I've seen smaller wires in other motors that are easier to damage.
If the break in the power flow is clearly visible, such as near a connection point, these can usually be fixed. If a winding wire had burned through and makes it too short to be reconnected, it can still be repaired. What I've done in this situation is to unwind one loop of the wire to get enough to be able to reconnect it. One less loop will not affect the function of the motor, but will allow you to make it work again.
  If the winding has no continuity and you don't see any obvious reason for it,  it's probably damaged further down inside. This makes it much harder if not impossible to repair. Because of how these are wound and assembled, you can't just unwind it until you find the break in the wire.
But the one that you can see, if it's just too short to be reconnected, can still be fixed. Carefully take the end of the wire and try pushing it back around the winding. You might have to use a small pair of needle nose pliers to grip it as you push it back through, but be careful that you don't damage the coating on the wire. It's see-thru, but it's still an insulation, and if damaged can cause a short if it touches something.
Also affecting your ability to repair a winding is which end of the wire was damaged. Because as the winding is made, obviously one end will be coming from the center where it was started, and the other end is on the outside. The outside loop of winding is the best one to have burned out,  because it's lot easier to unwind. The inside loop is pretty much impossible to unwind. So you need to look closely at it before you try a repair on a winding.


A bad connection on the armature can also sometimes be repaired. It depends on exactly where it's at, and if it's just a melted solder joint, or if a wire has been burned through. A solder joint can usually be fixed. A burned wire will depend on where it happened and if a loop of wire can be un-wound to enable it to be reconnected.
Unlike the two field windings, there are many more armature windings,  and they are wound one over another. If you're lucky, it'll be the last winding that was done. If it's not, it's probably not worth the effort. I have gone through the process of unwinding each segment of windings to get to the bad one, then rewinding each one, but it's extremely difficult and time consuming. And any damage to the insulation is a possibility of a new problem.
  You also have to use the original wire, or find an exact match to it, and it's not a regular wire. It's typically what is called a "non-magnetic" wire, which most places don't carry.
So I'll stick with the easier and more obvious problems, but I wanted to make sure you know what things you should look for if you want to try this.

CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

#5
  So now I've got the housings painted,  and the rust on the field windings cleaned off. I've removed the bad wires that feed the motor and have soldered new wires in place.
Once I get the other ends of the new wires inserted through the grommets in the bottom housing,  I'll get the field winding installed in the housing. I test fit it after I cleaned everything up and it goes right in place with no problem, unlike the removal process.


More to come, this is as far as I got yesterday.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Lexi

Rick, great stuff & photos. Have a question though. If your mast is bent, (think from years of wind blowing them out of shape while on the road), is there a way to reasonably straighten them? Clay/Lexi

Cadman-iac

#7
Hi Clay,
Great question, but unfortunately I've never messed with the mast portion of an antenna as of yet. I've been kicking around taking this one apart. It is still functional, so it's not really necessary to do anything with/ to it. But I'm curious about how this part of it works. I just don't want to cause any damage to it in the trying.

My purpose in posting all this was to give people an option to fix their own motor if they are so inclined.

However if anyone has any experience with the mast half of these antennas, you're welcome to post your advice on here if you'd like,  or please start another thread on the topic, because I would guess that 4 out of 5 antenna issues/problems are with the mast, and I'd like to know what to look for and how to perform the repairs on one, as I am sure others would too.

Thanks for your question Clay, I'm sorry I can't give you an answer.
      Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

#8
   So after running the new wires through the grommets, I installed the field winding. When you do this  use the bolts to keep the winding lined up correctly. Also while it's going in, make sure you keep the new wires in the grooves on each side of the winding. See the first picture.
Once the winding is seated, then insert the small washer that goes under the shaft, and install the little ball bearing into the end of the shaft. Use just a dab of grease to keep the bearing from falling out as you install the shaft. Second and third pictures.
After the shaft is in place, push the bolts all the way through until the square head locks in place. Then you can put the tubular spacers over the bolts. These position the brush plate.

Reinstall the brush springs and brushes, tying them in place to help free your hands. See the fourth picture.
  You can see the breaker in this picture really well. The brass piece to the right of the breaker is where the circuit grounds on the bolt.
Place the brush plate over the shaft, being careful that you don't knock one of the zip ties loose. Then install the lock washers and nuts that hold it in place.
Note that I haven't reconnected the brush to the field wire yet. It's a lot easier to install the brushes on the plate and the plate onto the motor when it's not tied to the wire. Once the plate is locked in place, then you can re-solder the brush to the field wire. Just be careful as you do this as the brush lead is braided, and it will wick your solder down it's length if you're not careful. This stiffens the lead and can prevent the brush from moving as intended. You will need to replace it if that happens.
When you have the brush reconnected, then release them if you haven't done so yet. Then slide the paper shield over the bolts. This piece is an extra precaution against the brush/ field wire shorting out on the top housing. See the fifth picture.
(I forgot to mention this paper shield earlier.)
Then the last thing to install is the top housing. Slide it down over the shaft and bolts until it seats against the bottom housing, and install the lock washers and nuts.
At this point, you should test it to be sure it operates correctly. Don't connect both wires to your battery or you will toast your motor. These are connected to each other at the brush.  Only connect one wire at a time to your positive terminal on the battery, and touch the housing or one of the bolts to the negative terminal on the battery. The motor should spin in one direction. Switch to the other wire and the motor should spin the other direction. If everything checks out, you're ready to install it on your mast assembly.
  Place the large O-ring on top of the motor housing to ensure it seals against the mast housing. (Sixth picture).
Put the small coupling on the mast driven shaft, then install the motor onto the mast housing, and make sure that you have the shaft flat spot lined up with the coupling. (Last picture).
  When all finished, retest your motor to make sure the antenna works properly. Then the last thing to do is crimp new terminal ends on your wires and insert them into the connector housing.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

#9
So that covers this style or design of antenna motor. I can't tell you what years this particular motor was used, but this one is out of my 56.
I tried to cover anything that might cause a motor to stop working, or only work partially. And I tried explaining the current flow so you could understand how it works.
I wrote it like what I would like to see if I were doing this without knowing what to look for. If it's a bit verbose, I apologize.
Thank you for allowing me to do this. I hope it's useful to someone.


I also have 4 or 5 of the type used on the late 60's and the 70's, but again, I'm unsure what years it covers either. (See picture).
I took one apart that was missing the mast. If anyone is interested, I can go through it like I did with the 56 motor.
Let me know.

  Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

D DOWNARD

I WOULD BE INTERESTED IN 1975 CADILLAC POWER ANTENNA OVERHAUL AS WELL. THANK YOU. DAN

Cadman-iac

  Thank you Dan,
  The next motor I go through will look like the last picture I posted just so you know.
  But it will be a while before I can get to it.

   Rick.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Roger Zimmermann

Interesting report! When I bought my '56 Sedan de Ville in 1982, the antenna motor was not functioning. At that time, I had not enough knowledge to do what you demonstrate here. I found at that time a company in Switzerland which repaired the motor. I don't know what was wrong. Anyway, it was rather expensive and the motor did function till I sold the car.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

The Tassie Devil(le)

When the Aerial in my '60 wasn't operating, I found ne from a '56 and using parts from both, made up a working one.   Nobody would know the difference once it was in the car.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Cadman-iac

#14
  Roger and Bruce,

I was pleasantly surprised to find that the motor, mast and cable were still working on my 56. I expected the mast would have been the first thing that would break on these.
Where would you ever find a replacement mast and cable if you needed one? Are they even available new, or would you have to find an intact used one?
  I've seen a couple of "rebuilt" complete antennas on ebay for $1000.⁰⁰-1200.⁰⁰.  For that price I would expect it to have a new mast and cable.

  I have been toying around with a couple of newer antennas from the 80's, and I noticed that the mast cable had a steel wire in the center of it, I'm guessing for strength.
  The few 60's-70's antennas that I have looked at had broken masts,of course, and the cables were just as bad. However some were solid plastic, and some were hollow, as if they were made to have a wire core in them.

  Another thing I noticed was in how the designers made the mechanism that allows the motor to continue to work when the mast reaches the end of its travel. The early 60's design, (at least I believe it's from this time frame, I only have one like it, and I can't remember what I removed it from, and I'll post a picture of it for reference when I can get to it), is like an overrun clutch, for lack of a better description. They used a spring loaded bar with a small ball bearing on each end that engages a pair of raised "bumps" on the cable drive, and when the cable stops moving the bearings jump the bumps and that's what you hear clicking away when the motor is still running after the mast has stopped moving.


  The 80's design antennas have a completely different way of keeping the motor from being damaged when the mast stops at either end of travel. They use a mechanism on the motors armature that engages a switch that breaks the power flow. When the mast stops, it causes a load on the drive gear that forces the armature to move up or down within the housing, and making this mechanism move with it, which breaks the power flow. Because there's no overrun clutch anymore, the only way to keep the motor from being damaged is to stop it from running. This mechanism only has to move a very short distance to break the contact, so the armature doesn't move far enough to disengage the brushes. The brushes, which are built into the switch assembly, are just a pair of tiny contacts welded to the formed copper arms that hold the brushes in position. Everything is made for easy assembly, not for quality or longevity. The housing for the motor and cable drive is plastic, and uses 4 pass-through rivets and 5 spring clips to hold it together, with silicone sealer between the halves to keep it water tight.

So over time they went from a high quality, repairable/rebuildable motor and drive unit, to this plastic, disposable, non-repairable piece that might last 10 years if you don't use it but once a week.

  I didn't take pictures of the newer unit at the time because I didn't think I would ever mention it here. Pictures would definitely help with my explanation of how it's designed.

   Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Roger Zimmermann

Many years ago, Klaus Wojak used to restore vacuum and electric antennas. They were expensive, with a new mast. It seems that he is still in business, even if is in his eighties. If I remember, during winter time he is in Florida.
Years ago, I bought a nylon string for 1956 antennas. Still have it on stock.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Cadman-iac

Hey Roger,

Can just the cable be replaced on one of these antennas? I haven't had mine apart that far yet since it does still work. I didn't want to break something in trying to disassemble it. 
But I was under the impression that the cable was permanently attached to the mast assembly, or at least the smallest diameter part of it anyway.
You wouldn't happen to want to sell your cable would you?

    Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Roger Zimmermann

Frankly, I don't know how it's attached. I opened the antenna from my '56 de Ville during the eighties, it's a long time back! Could be that the wire is crimped at the smallest diameter part. I will not remove and disassemble the antenna from my '56 Biarritz to check!
Send back the nylon wire to the US? Why not? I'll tell you what I paid at that time (that wire came from Ted Holcombe when he sold his parts inventory as he sold his '56 car) with an email.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Roger Zimmermann

By looking at the material I have, the question "How" is solved: the nylon cord is firmly attached at the smaller mast; this part is included with the cord. At the end of the mast, there is a thread for the ball.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

The Tassie Devil(le)

With these days of good glues, and such an array of nylon material to use, the hardest part of replacing the "string" would be getting the old stuff out of the mast without damaging it.

I think that without the invention of weed wackers/whipper snippers, there would be less of that nylon "string" around.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe