1971-1976 General Motors Full Size Convertibles (commonly known as "Scissor Top" Convertibles) feature a unique mechanical (non-hydraulic) power lift system. When these "Scissor Top" convertibles don't perform as expected, it is often challenging to pin down the issues responsible for the malfunction.
Scissor top models include 1971, 1972, 1973, 1974, 1975, 1976 Buick Lesabre And Centurion, Cadillac Eldorado, Chevrolet Impala And Caprice, Olds Delta 88 Royale, Pontiac Catalina And Granville Convertibles
In this post we hope to provide a little guidance in troubleshooting these troublesome mechanisms.
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Issue: Slow or inoperative scissor top:
It’s easy to assume that the problem is the motor, but, friction from worn parts is the most common cause for a good motor to not be able to operate the top. Often it’s not just worn side rails or side gears, but a combination of several of them being worn at once. See “Worn Side Rail test”, “Worn Side Gear test” & “Bad switch, relay or motor” tests below to be sure.
Issue: #2 Bow folds incorrectly when raising top (one side goes forward toward the header bow):
Two things control the position of the #2 Bow; See “Worn #2 bow side brackets” & “Side Hold Down cables” below.
Issue: Only one side of top operates:
One Drive Cable may be loose or broken. Inspect both, first at the side gears, then at the motor behind the rear seat back. If drive cables are functioning, perform the “Worn Side Gear test” below, on both sides.
Issue:Top guide pins won’t reach forward enough to drop into holes on the windshield:
1. Side rails not adjusted or bent. Follow Fisher Body Manual adjustments. If problem persists, bent side rail may need replacing. 2.Top material may be too tight at the header bow, in the rear quarter, or both. If it is, loosen the top, if possible, or install a new top after properly adjusting the frame. Also, see if tightness of rear window curtain on the #4 bow is holding the outer rear rail assembly back. 3. If only one guide pin can’t be pulled into it’s hole, try resyncronizing drive cables so that the bad side comes up to the windshield a little sooner than the other side.
TESTS TO HELP YOU FIND WHICH PARTS ARE BAD:
Worn Side Rail test: With top lowered 2 feet back from windshield, one side at a time, grab the front of the side rail and move it up and down. If there is more than 2 inches of play (caused by slack at the side rail elbow pivot), the side rail has too much wear.
Worn Side Gear test: With the top folded all the way down, disconnect the drive cables and unbolt the side gears from the 3 inch siderail links. Grab the side gear appendage and force it through it’s travel, all the way forward and all the way back. A worn side gear will either bind up at one or more points (going in either direction), or, will move too freely in either direction. A good side gear will have constant firm resistance throughout travel in both directions.
Worn #2 Bow Side Brackets: Check for play where pivot ball/rivets swedge to the bracket; also, see if bracket is bent.
Side Hold Down Cables: Each side cable should have a 2” shunt cable attached to the #2 bow. See if it’s disconnected or broken, or, if the ends of the #2 bow core substance can no longer hold the cable screw. Replace side cables or #2 bow.
Bad Switch, Bad Relay Or A Bad Motor?: Click here to download our Scissor Top Motor, Switch and Relay troubleshooting tips!