Rehab/repair of sequential motor assembly

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gbird66
Posts: 70
Joined: Sat Sep 19, 2015 1:12 pm

Rehab/repair of sequential motor assembly

Post by gbird66 » Thu May 12, 2016 9:38 pm

I know redstangbob did a very in-depth write up about repairing the various sequential motor, relays, and such back in October of 2011. What I am presenting here is how I disassembled the sequential motor down to its component parts, including the reduction gear box.

First, let me start off by saying that for most of the 1990's I was a 35mm SLR repair technician as well as a Sony 8mm camcorder technician. Most SLR's built from the mid 80's up through the 90's had miniature DC motors that would fail for various reasons. I became very good at rehabbing motors as a result and want to share some things that might help someone with a bad sequential motor assembly repair theirs rather than replacing with another used one or going electronic, if only for originality sake.

To start off, many DC brushed motors will wear out the carbon brushes over time with use and their continuous contact with the commutator. If the carbon builds up on the commutator, it can cause the resistance to increase to the point that the motor will either slow down, stall after a bit, or quit altogether.

I am fortunate enough to have an NOS sequential motor to use to take resistance measurements from as a baseline. Shown here is the NOS motor on the left and the used one that I tore down on the right:

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First I put the lead of my ohmmeter on the positive motor terminal (at the motor itself) and the other lead to the black ground eyelet. On my used motor the reading fluctuated between 100 ohms and up. What I am measuring is the resistance of the three field windings in the motor, through the carbon brushes against the commutator. I then measure the resistance of the NOS motor and it is 66 ohms. That sounds about right for a motor of this size and voltage - again, from years of testing various small DC brushed motors.

Before I go any further, let me say I did not take a picture at every step of this process but I feel anyone can follow along with the pics given. Also, for most repairs it will not be necessary to separate the motor from the gear box to check the resistance of the individual field wings and to inspect the carbon brushes, but I went full tilt and pulled everything apart just to do it.

This is the inside of the cam and switch assembly after removing the plastic white cover:

Image

I desoldered the brown wire at the base of the motor so that I could free it from the main body. I then pried the white "camshaft" off of the motor shaft. I laid a small screwdriver against all off the switch contacts so that none of the switch actuating tabs/arms are contacting any of the cam lobes. I then used a pair of needle-nose pliers and wedged it between the rear of the camshaft and the back of the assembly where the motor retaing screws are. I slowly worked the needle-nose aginst the back of the switch housing and eventually pulled the camshaft free of the motor shaft. The motor shaft and camshaft are "keyed" so that it will not slip on the shaft while in operation. I then removed the three motor retaining screws at the back of the main housing and worked the motor shaft clear of the main body.

To inspect the inside of the motor and to access the motor windings, commutator, and carbon brushes, I as carefully as possible wedged a small flat blade screw driver between the base of the outer motor "can" and the base of the gear box assembly. There are two dimples on the outside bottom of the can 180 degrees apart that anchor the can to the main gear assembly.

With the motor separated from the main body and the can removed, you can see the black carbon "dust" that has accumulated inside:

Image

Image

I wanted to check the resistance of each of the three field windings to make sure there were no open windings (which would have given an "infinity" or open reading on an ohmmeter). I placed one meter lead on a copper commutator section and the other lead on the cummutator section next to it. I did this three times and came up with the following ohm readings:

1) 62 ohms
2) 72 ohms
3) 81 ohms

Okay, with a 10 ohm deviation amongst the three, the windings don't appear shorted. Had I received an open or infinity reading at any time, I would have gone no further: For all intents and purposes the motor would have been unrepairable.

In this pics you can see that the commutator has blackened due to contact with the brushes:

Image

The next steps will most likely not be necessary for most; Tearing down to gain access to the inside of the reduction gear box. I used a 1/16" drill bit and from the back side of the motor drilled out the three rivets. Note that I did not drill all of the way through to the other side as that has the retaining screw threads and I did not want to damage them. I carefully drilled down enough to where the flared end of the rivet was no longer holding the two halves of the gear box together and pried the two halves apart.
To make it easier to free the motor windings and commutator free of the brushes, I had to pry the gear on the end of the motor shaft off. I carefully placed two flat blade screwdrivers 180 degrees apart between the underside of the gear and the back plate of the gear housing. Once that was done, I removed the gears and camshaft spindle from inside the other part of the gear housing and removed the windings free of the motor base:

Image

I then went about freshening the surfaces of the commutator sections. I used a Dremel tool with a wire brush attachment and carefully burnished the surfaces to remove the built up carbon. I also went about cleaning all of the old gear grease off of the gears and from inside the housing. Again, it probably will not be necessary to do this but since I had it apart I wanted to start fresh. I should mention that before I removed the gears from the housing, I put the two halves back together (sans motor of course) and twirled the camshaft gear shaft by hand and it moved rather freely or without what I would consider undo effort.

I very carefully took a miniature file (one of several tools from my camera repair days) and burnished the faces of the carbon brushes. I should add that, in my opinion, there was a lot of life left in these brushes based on the length (or width if you please). If they were worn down to almost nothing, i.e., where the brush tabs would rub on the commutator then this motor would not really be serviceable - although I have gotten creative in the past in similar situations and was amazingly able to "MacGiver" it with new carbon pieces. Also, if the brushes were worn down significantly, then the commutator would most like have a valley cut into it where it too has worn.

To remove all traces of carbon from the windings, the brushes, and the gears and gear box, I use CRC Mass Air Flow Sensor Cleaner. It has great flushing action, evaporates quickly, and does not harm any of the plastic:

Image

I used a little 3-In-1 oil to lubricate the bronze bearing surfaces at both ends of the motor shaft. To replace the grease in the gearbox, I used a camera/video grease called "Losoid" that is compatible with metals and plastics. If I did not have that, I could have used a very sparse amount of bearing grease or even petroleum jelly.

I put the motor windings/shaft carefully back in place in the end of the back half of the gear box, being very careful to pry the brushes away from the commutator as it is slid in place. I carefully tapped the gear previously removed from the end of the motor shaft back in place and reassembled the two halves of the gear box. I carefully twirled the windings/shaft by hand to make sure there was positive engagement of all of the gears, no binding, and to verify that the camshaft shaft turned as I turned the motor windings/shaft.

Now the next issue I faced was how to hold the gear housing together - remember, I had to drill out the rivets. I have a huge assortment of tiny screws of various sizes and lengths from my camera repair days and I was fortunate to find three screws with a course thread (originally used to secure the top and bottom plastic camera covers to the main body). If I did not have these screws, then I would have searched for three appropriate sized roll pins and tapped them into the housing:

Image

Now before I proceed any futher, I want to make another ohmmeter reading to check on the overall "health" of the motor. The pre-repair readings were over 100 ohms and were not consistent. The NOS motor read 66 ohms. The motor now reads 80m ohms - much better than before. I applied about 13.5 volts to the motor with my bench DC power supply and it hummed along nicely. I tried to squeeze down on the camshaft shaft with my fingers to see how much effort was required to stall it. I had to pinch really hard to almost stall it so that is a good sign. At no load on the shaft, the current draw was minimal - another good sign.

I now turned my attention to the switch contacts assembly. I used my small file between the contact halves on all four switches. I then used the CRC Mass Airflow Cleaner to blast out old dirt and metal shavings. I then secured the motor/gear box assembly back to the main switch housing with the three retaining screws. I put a small amount of grease on the shaft to make sliding the camshaft back on it easier. I pushed in until I could see that all four switch actuating tabs were centered under their respective cam lobes. I then put a light coating of grease on the cam lobes:

Image

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I clipped my positive lead from my power supply to the tab at the base of the motor and hooked up the negative lead to the black ground eyelet wire. I set the voltage to 13.5 volts and turned on the power. The whole thing clipped along at a steady pace. I let it run for a couple of minutes to make sure I didn't detect any strange sounds from the motor like varying speed, weird noises from the gearbox, etc. I the turned the power off an on several times, waiting a moment between off and powering it back up. I want to make sure it will start without fail each and every time. I then resoldered the brown positive wire back to the positive tab on the side of the motor. Even though not shown, the original clear heatshrink tubing was brown from age. I will place new, clear, heatshrink tubing over the wire where it is soldered to the tab on the motor.

The final test I did was to determine the "stall" voltage of the motor. As anyone with sequential has probably noticed, as the car idles for any amount of time the lights sequence slower than they do off idle. I slowly turned the voltage down until the motor stalled; in this case, the stall voltage was about 6 volt. This reasonably assures me that the sequencer won't quit during an extended idle time, especially if the headlights, taillights, and brake lights are all on.

Well, I hope this wasn't too long winded. Any questions, concerns, criticisms are welcomed.

Greg
1966 Town Landau
25k original miles

RAVEN
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Re: Rehab/repair of sequential motor assembly

Post by RAVEN » Thu May 12, 2016 10:03 pm

Let me be the first to thank you, and state the article you wrote was wonderful. It is an addendum to redstangbob's article, and a pleasure to read. The detailed info about the motor and gearbox added needed insite.

Wally
CDN Member since 1975 #2086
Flock: 1964 Landau Original Family Owned
1964 Sr Convertible "RAVEN"
Past: 2003 Blk Lab "RAVEN" "RIP"Nov 15/17
1964 Lincoln vin4Y86N00007
1964 Red Convertible

gbird66
Posts: 70
Joined: Sat Sep 19, 2015 1:12 pm

Re: Rehab/repair of sequential motor assembly

Post by gbird66 » Thu May 12, 2016 10:34 pm

Wally,

Thank you. I appreciate the kind feedback. I cannot stress enough, how my years as a camera repair bench tech opened all kinds of avenues for repairing/restoring electro-mechanical devices (many sealed and "unrepairable") such as AC/DC motors, discrete stepper motors, relays, solenoids, car clocks, power window switches, switched=-mode/PC power supplies, etc. I enjoy the challenge each and every time and I like to share what I've learned over the years so that someone who wouldn't normally tackle something like the sequential motor can feel that it is do-able.

Greg

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paulr
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Joined: Mon Nov 05, 2012 12:03 pm
Location: Seattle

Re: Rehab/repair of sequential motor assembly

Post by paulr » Fri May 13, 2016 10:44 am

This is fantastic! Thanks.

I did this on the '65 a few months back, though mainly it was a cleaning affair without any need for resoldering contacts, etc.
To replace the grease in the gearbox, I used a camera/video grease called "Losoid" that is compatible with metals and plastics. If I did not have that, I could have used a very sparse amount of bearing grease or even petroleum jelly.
Really appreciate this info; I've been nervous to apply the wrong thing. My unit has been getting noisier after perhaps too aggressive cleaning.

The extra detail is great. This could be a Scoop article if it hasn't been covered already.
Paul
VTCI 12014
Registry 45122
'64 Landau HT
"Beer, now there's a temporary solution!" ~Homer Simpson

RAVEN
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Joined: Sun Sep 09, 2012 10:33 am

Re: Rehab/repair of sequential motor assembly

Post by RAVEN » Fri May 13, 2016 2:07 pm

The mentioned lube is a new replacement product, for me to considering to use on the speedo/odo gears. I will now use "IT", to replace the high temp valve lubricant silicone based product currently used.

Every story seems to have a happy ending.

Wally
CDN Member since 1975 #2086
Flock: 1964 Landau Original Family Owned
1964 Sr Convertible "RAVEN"
Past: 2003 Blk Lab "RAVEN" "RIP"Nov 15/17
1964 Lincoln vin4Y86N00007
1964 Red Convertible

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Alan H. Tast
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Joined: Wed Aug 20, 2003 10:52 pm
Location: Omaha, NE

Re: Rehab/repair of sequential motor assembly

Post by Alan H. Tast » Fri May 13, 2016 10:10 pm

I think you can predict what my next sentence will be. This needs to be prepared for publication in "Thunderbird Scoop," preferably in conjunction with Redstangbob's article. So, gentlemen, please contact/PM me so that I can coordinate and start preparation work. Thanks.
Alan H. Tast, AIA
Technical Director/Past President,
Vintage Thunderbird Club Int'l.
Author, "Thunderbird 1955-1966" & "Thunderbird 50 Years"
1963 Hardtop & 1963 Sports Roadster

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60fore
Posts: 2159
Joined: Mon Jun 04, 2007 7:17 pm
Location: Edmonton, Alberta

Re: Rehab/repair of sequential motor assembly

Post by 60fore » Sat May 14, 2016 1:41 pm

Another great tutorial by one of our own! Never ceases to amaze me, the ingenuity and varied talents of our forum members.

But one question on my mind, as I'm sure it is on some others is : did you really gain 4-10 hp at the wheels from using this spray?

Image


:lol:
Currently Birdless....we'll see how long that lasts!

Past Birds: 1962 Hardtop Corinthian White "The Survivor"
1964 Hardtop Gunmetal Gray "60Fore"
1986 Turbo Coupe Regatta Blue

john6t6
Posts: 437
Joined: Wed Oct 01, 2003 2:42 pm
Location: Alberta, Canada

Re: Rehab/repair of sequential motor assembly

Post by john6t6 » Tue May 17, 2016 4:46 pm

Great write-up, excellent gbird66.
1966 Hardtop Sauterne Gold
VTCI #4065

jstrull66
Posts: 72
Joined: Wed Jan 25, 2017 5:39 pm

Re: Rehab/repair of sequential motor assembly

Post by jstrull66 » Wed Apr 24, 2019 1:29 pm

Thank you for a Great source of information.

I have had problems with the turn signals, they work when first turned on but quit working if I step on the brake pedal, or sometimes they quit working if I do not touch the brakes, so I am thinking Electronic turn signal, till I saw this good article, so maybe it needs a cleaning of the cam and contacts perhaps? Will get that mass air flow cleaner and some spray grease.

Again Thank you gbird66 most appreciated
John T.

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