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Join Date: Oct 2004
Posts: 540
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Convertible top control unit failure??
I'm getting no response from my 1987 Carrera convertible controls. I've put the top down about 3 times in two years. It worked yesterday and today it doesn't.
In the closed position, activating the top switch does nothing. The two microswitches on the single control motor ohm out good. Power is getting thru the top switch. I manually released the locks and lifted the top slightly. The two microswitches on the lock motors ohm out good also. Still no response from the switch in either direction. About all that is left is the control unit. Does it have a bad history of failing? Does anyone have a schematic or some trouble shooting hints? Does anyone have a name of a company who could check out the unit? Thanks. |
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06-21-2011, 09:07 AM
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RETIRED
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Under powered and failure prone. Jumper it and see if it responds...no go, pull it have it rebuilt or replace.
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1983/3.6, backdate to long hood 2012 ML350 3.0 Turbo Diesel |
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06-21-2011, 09:19 AM
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Join Date: Jul 2005
Location: Haarlem area, Netherlands
Posts: 212
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Relays in the control unit tend to get faulty; they are mechanically built the same as the relais in the DME relais box. This means they mechanically get stuck just before electrically connecting the contact points.
While pushing the button to open the top, stamp your right foot (or your left, but more difficult  ) heavily in the passenger side footwell, this usualy triggers such hesitating relais in the unit to engage (for the 3.2 the control unit is behind the wooden panel in the lower footwell). If this works, one or few relais are causing the trouble. It was quite funny for a while to ask support of an occasional passenger "please stamp your feet to help me open the top".But I eventually replaced the relais in the control unit as an evening DIY job. You probably wont find parts that fit the space of the original ones on the circuit board; so it does require a bit a creativity to wire them in place. Cost me roughly 25 bucks for 5 new relais. Alternatively spend a lot of money for a new control unit.
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Better a good one for a lot of bucks, than a bad one for little Last edited by lindemans; 06-24-2011 at 12:58 AM.. |
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06-23-2011, 11:23 PM
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Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
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"Relays in the control unit tend to get faulty; they are mechanically built the same as the relais in the DME relais box. This means they mechanically get stuck just before electrically connecting the contact points."
Actually, those relays are very reliable and rarely (never) fail in that ECU.
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone |
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06-24-2011, 07:02 AM
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Join Date: Jul 2005
Location: Haarlem area, Netherlands
Posts: 212
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The DME relais under the seat is well known for its failures, isnt it ?
The relais in the control unit for the convertible top are the same as the 2 relais inside the DME relais unit. I have had 2 of those sticking mechanicaslly before engaging the contacts.
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Better a good one for a lot of bucks, than a bad one for little |
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06-24-2011, 07:49 AM
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Join Date: Jul 2011
Posts: 2
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We have a 93 963 Cabrio right now with the same problem. Are the relays located in a different spot than the late 80s cars? We looked under the carpet on the passenger side and didn't have any success there. Pretty frustrating!
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07-19-2011, 09:52 AM
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Join Date: Jul 2011
Posts: 2
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Correction *964
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07-19-2011, 09:53 AM
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Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
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"The DME relais under the seat is well known for its failures, isnt it ?"
Module itself fails, but NOT the relays inside! "Are the relays located in a different spot than the late 80s cars?" "Relays"? The Cab Top ECU is under the left side of the dash by the air vent.
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone Last edited by Lorenfb; 07-22-2011 at 08:40 AM.. |
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07-22-2011, 08:37 AM
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Da cab
