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41' Cadillac starter issue

Started by 41coupe, November 02, 2014, 07:52:46 PM

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41coupe

I am in need of some technical help. Recently, out of the blue, when I turned on the battery cut off switch to power up the car, the armature on the starter began to spin. The ignition was not on, nor did the solenoid engage. It appears like an electric motor running. I removed the starter and tried testing it on the bench, and each time you touched a jumper cable to starter terminal, and then grounded the housing, the armature began to spin. I took the starter to a rebuilder familiar with these older parts, and he could find nothing wrong. He conducted his bench test, showing me that everything was operating normally. The solenoid engaged properly, and a load test showed the starter was fine.  I installed the starter, and it worked normally for two days. Today, I moved the car out of the garage without a problem. A few hours later, when I again flipped open the battery cut out switch, the starter began to spin. I bypassed the cut off switch, but as soon as power was sent to the starter terminal, it would spin away. With the negative battery terminal attached to the starter, and you touch the positive cable any place on the engine block, the starter spins.
Is there some kind of short inside the starter? Any ideas will be greatly appreciated.    Thanks   Phil

Steve Passmore

On the rear of the solenoid are two large round discs contacts normally kept apart.  No power go's to the armature until they touch. When the start button is pressed power energizes the solenoid relay so driving the solenoid one end of which engages the starter drive into the flywheel, the other end engages the two brass discs so allowing power to turn the armature.   Until these discs touch theres no power to the armature so I would be looking at this disc area to see if the return is not working or if these discs are somehow burning and sticking together ocationally.
Steve

Present
1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

Previous
1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe

41coupe

Thanks   I will remove the starter, and disassemble the solenoid to check the two discs.   Phil

Bill Ingler #7799

Hi Phil: To add to what Steve has said, as you are looking at the solenoid, look at the insulation board that you see behind the starter stud mounting plate ( right stud) on picture 1 below. Then look at the missing insulated board behind the battery stud(left stud). That missing board makes the metal plate around the battery stud hot and gives power across that metal plate to the starter stud . So I would also look closely at that area and the possibility that with what Steve has said and any intermittent loose connection or missing a part of the insulation board, might give intermittent power to the starter and is the answer to your problem when you turn on the battery cut off switch. Picture 2 is the normal connections for the starter solenoid, picture 3 shows the large brass disk that joins power to the battery and starter studs. Bill

Steve Passmore

Bill has a very valid point to check that insulation first.  Could save you some work.
Steve

Present
1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

Previous
1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe

41coupe

The photos are great. Now I know where to look. I will let everyone know what it turned out to be.