| Author | Message | ||
     Carl Jensen Experienced User Username: carl_jensen Post Number: 35 Registered: 2-2005 |
I just don't get it. Some of my heater/air conditioning actuator motors (usually the upper temp. flap) intermittently will run continuously. I have gone through everything I know to do - replaced and rechecked the 7 fuse board diodes and the diode on the back of the ACU. All are perfect. I also cleaned the multiple connectors on both the left and right sides of the firewall (to correct low current going to some of the actuators) and then removed and inspected the ACU (after removing the dust covers I couldn't see any problems as I rotated the switches, but I sprayed on a bunch of electrical contact cleaner in case some of the contacts were dirty). The really weird part is that with all 7 fuse box diodes completely removed, the actuators still get activated when I operate the temp. and quantity switches! I must really be missing something here. If anyone can help with suggestions it would be appreciated. I guess that my next move is to purchase a new ACU, but that will run about $1300 and I may be just throwing my money away to replace a switch that isn't faulty. That would really hurt. Thanks, Carl Jensen | ||
| David Gore Moderator Username: david_gore Post Number: 934 Registered: 4-2003 |
Carl, the diodes are not intended to act as circuit breakers or fuses so it is OK for the electrical components to continue to function when the diodes are removed. The purpose of the diodes is to stop stray electrical currents from other components finding their way to other components and causing them to actuate unexpectedly and/or vice-versa. It is most important that the diodes be installed with the correct polarity; if they are installed in reverse, the problem will continue to exist. Now for the part where you start tearing you hair out - not all of the diodes are on the main fuseboard; they can also be taped up in various parts of the wiring loom as a consequence of undocumented running changes during production to solve individual problems as they arose. This may OR may not be a factor in your problem. I am aware of another owner in your part of the world having similar problems some years ago and he traced the problem to diode 7 on the fuseboard. The diode had burnt out and he replaced the diode without fixing the problem. He then checked the back of the circuit board and found the connections had burnt out when the diode failed. Cleaning the board and resoldering the connections fixed his problem. I have forgotten the polarity orientation for the diodes and hope someone can provide this information. In the meantime, the first thing I would do is get a new diode and install it in position 7 [bottom of fuseboard] with the positive end [longer lead] on the LHS terminal then test the system. If the motors are still running; reverse the diode so the long lead is on the RHS terminal and test again. If unsuccessful, try disconnecting the leads to the water tap actuator and see if this stops the flap actuator motor [beware of short circuiting the live leads.] If this is successful, you need to troubleshoot the wiring from the water tap to the actuator to try and find any hidden diodes. I very much doubt purchasing a new ACU will solve the problem - my money is on either wrong polarity diode installation or a failed diode hidden in the wiring harness. (Message edited by david_gore on 08 March 2010) | ||
| John Kilkenny Frequent User Username: john_kilkenny Post Number: 99 Registered: 6-2005 |
Carl, The purpose of the seven diodes is to prevent unwanted connections through the upper system switch segments or actuator contacts causing faulty operation. However some of the upper actuators will still work without the diodes including the upper temperature flap actuator. A likely cause of an actuator cycling continuously is when two of its inputs are on together. If more than one of your actuators is exhibiting the fault it will be necessary to see what they have in common. Incidently Diode 7 is used to reset the Upper Temp Flap Actuator when the Aircon is operating and prevents feedback into the Bulls Eye Actuator when the Aircon is off. If this diode was shorted it would cause cycling of the Bulls Eye Actuator when the Upper Temp Switch was in the Off postion. Regards, John | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 36 Registered: 2-2005 |
Thanks very much David & John. I believe this will send me in the right direction (and away from purchasing a $1,300 switch). Thanks! Carl | ||
| Phil sproston Unregistered guest Posted From: 203.45.216.19 |
Carl Check the fuses ends in the middle of the fuse board has blue paper between them if not cut up a business card to stop the ends hitting. This can fix a lot of electrial faults. (Message approved by david_gore) | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 549 Registered: 6-2006 |
Carl, just a couple of thoughts. If the plugs on the back of the switches are fitted one or two holes along, it can give strange results and can connect actuators together in 'wrong pairs' and also give double feeds which does cause odd results. (wouldn't really be intermittent) Any jammed or seized actuators will in some switch positions cause feeds back through the rest of the wires from that actuator. Each actuator should only have one feed at the plug JK has gone through what the diodes try and do, but it is confusing. Until the actuators reach a stop point , it will feed back through it's other wires - these feedbacks will reach the any other actuator on the same circuit. That actuator will also be running and feeding back. There is so little chance of both actuators reaching their stop points at the same moment, that they will just keep feeding back to each other - and keep running forever. The diodes separate the feeds so that one of the pair of actuators only gets fed from the switch - when that actuator stops, the other one can finish it's cycle and stop. Later cars have diodes to both actuators in case of jammed actuators. Upper temp flap act is linked to the bulls eyes flap act. Have you tried unplugging that and seeing if the Upper temp flap stops? So make sure they are both operating. If you can't find the relevant diode, you could add diodes to each feed wire of the offending actuators opposite number. (make a note of where you put them, and add to the service history though :/ ) | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 37 Registered: 2-2005 |
Thanks again for everyone's helpful advice. I went ahead and put diode 7 in backwards, but the problem continues with the continuously-cycling upper temp. actuator. I also put a thick slice of paper between the fuses in the middle of the fuse board (very interesting suggestion Phil). I couldn't find any extra unexpected diodes taped to the wiring harness but must admit that I didn't really tear things apart to see all of the harness. Paul also had intersting advice about other actuators that may be jammed feeding back to affect the upper temp flap, so I went ahead and disconnected all of the other actuators and the problem with that one cycling actuator persists. It looks as if I have exhausted almost all other avenues, so I went ahead and ordered a new ACU switch assembly. If that doesn't work ($1300 later) then the screams you hear coming from Texas will be mine. Thanks again to everyone. I'll report back once the new ACU is installed. Thanks, Carl | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 556 Registered: 6-2006 |
Carl, Without reading all the way back, have you tried another actuator in it's place? Has it got two (or more) feeds going to it? what colours are the wires going to it and which are live? Why not get a used switch instead? (if it's not too late to cancel the switch - pm me) | ||
| Carl Jensen Experienced User Username: carl_jensen Post Number: 38 Registered: 2-2005 |
Whoo Hoo! I finally took the plunge and bought a new acu switch. And......the flaps now work fine! I can't tell you how relieved I am that I didn't throw away $1300 for a new switch that wasn't needed. Thanks very, very much to Paul, David, Phil and John for your helpful advice on diagnosing this problem. It was a tremendous help to try all possibilities before I took the plunge and ordered a new switch. To me, this is what the RR Forum is all about and I can't tell everyone how much your help was appreciated. Now I'm a whole lot poorer but a thousand times happier at how well my car is now running (this is a brief moment in time before another challenge occurs, but that's OK). Thanks! Carl Jensen | ||
| David Gore Moderator Username: david_gore Post Number: 944 Registered: 4-2003 |
Great news Carl - just keep driving your car as much as possible; it will love you for it and the number of problems will decrease exponentially. Just remember, your car was meant to be driven rather than being a "garage queen" .  | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 824 Registered: 9-2004 |
Actuators going crazy,checked diodes all ok. Problem caused by the lower column flap jamed out of its housing causing the actuator to jam giving incorrect signal. Cold air in abundance (Message edited by pat lockyer on 21 September 2010) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 825 Registered: 9-2004 |
How many Shadows are going around with the actuators disconected due to this failing of old rubbers dropping out.This causes the flap spindles to drop with other related faults.  | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 826 Registered: 9-2004 |
forgot the old rubber spindle mount,or whats left of it.  | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 663 Registered: 6-2006 |
Hopefully not too many! The new bushes are of a much better material. The old ones were made of the same material as early front panhard rod bushes. Possibly gelatine based! | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 827 Registered: 9-2004 |
Needless to say I have a modefied type and also done a mod to stop the spindles ever dropping out. Have also made and fitted new sponge seals. |
