Volvo Owners Club Forum - View Single Post - S40 (New) Electrics :

dilbertov · May 18th, 2017, 09:12

Great guide - thanks. A few comments from my experience which may be helpful to others:

1. On mine, pressing the boot release (physical and remote) made a short (<1s) buzzing noise. It sounded like the lock was trying to work. Everything else worked (number plate lights, no "Boot Open" warning on dash) so I assumed - incorrectly - that the loom was OK and the lock was faulty.
2. I therefore crawled into the boot, removed the trim panel, the wiring plug from the lock, and the 3 bolts attaching the lock to the boot lid, then opened the boot.
3. Due to the design of the lock, the electrical socket moulding on the lock fouls the retaining bracket when opening the lid. Forcing the lid open cracked the plastic around the socket. This was successfully repaired with a high quality cyano adhesive (superglue).
4. The lock seemed to be working fine (dismantled, manually operated and visually inspected it) so I stripped out the loom and found the main +12V feed to the mechanism (Pin 4 on body plug, Pin 1 on lock plug) to be connected by only one strand. The earth wire (Pins 1 and 2 respectively) was in similar condition. Probably the voltage drop/high resistance over the two bad cables meant the lock motor was drawing some current (hence the sound) but not sufficient to activate.
5. As all the cables in the harness would be work-hardened and brittle I took the decision to replace with a new one rather than repair. The new one sorted the problem.
6. I was disappointed by the quality of the new (genuine) loom - £42. Cables were hard and stiff and some of the body cable fixtures were out of position making fitting poor. Any loom subjected to repeated movement should be made from small cross-section multistrand - say 0.08mm x 60 - and preferably in a silicone sheath. Incidentally, I had these exact same problems on a 2007 Citroen C4 I owned where all door hinge looms and tailgate were failing for the same reason. If I still have my Volvo in 5 years time (otherwise very happy with it, so hopefully will) I will be expecting to have to replace the loom again when the inevitable happens.

May 18th, 2017, 09:12	#30
dilbertov New Member Last Online: Aug 2nd, 2020 09:42 Join Date: Mar 2017 Location: Portishead, Bristol	Great guide - thanks. A few comments from my experience which may be helpful to others: 1. On mine, pressing the boot release (physical and remote) made a short (<1s) buzzing noise. It sounded like the lock was trying to work. Everything else worked (number plate lights, no "Boot Open" warning on dash) so I assumed - incorrectly - that the loom was OK and the lock was faulty. 2. I therefore crawled into the boot, removed the trim panel, the wiring plug from the lock, and the 3 bolts attaching the lock to the boot lid, then opened the boot. 3. Due to the design of the lock, the electrical socket moulding on the lock fouls the retaining bracket when opening the lid. Forcing the lid open cracked the plastic around the socket. This was successfully repaired with a high quality cyano adhesive (superglue). 4. The lock seemed to be working fine (dismantled, manually operated and visually inspected it) so I stripped out the loom and found the main +12V feed to the mechanism (Pin 4 on body plug, Pin 1 on lock plug) to be connected by only one strand. The earth wire (Pins 1 and 2 respectively) was in similar condition. Probably the voltage drop/high resistance over the two bad cables meant the lock motor was drawing some current (hence the sound) but not sufficient to activate. 5. As all the cables in the harness would be work-hardened and brittle I took the decision to replace with a new one rather than repair. The new one sorted the problem. 6. I was disappointed by the quality of the new (genuine) loom - £42. Cables were hard and stiff and some of the body cable fixtures were out of position making fitting poor. Any loom subjected to repeated movement should be made from small cross-section multistrand - say 0.08mm x 60 - and preferably in a silicone sheath. Incidentally, I had these exact same problems on a 2007 Citroen C4 I owned where all door hinge looms and tailgate were failing for the same reason. If I still have my Volvo in 5 years time (otherwise very happy with it, so hopefully will) I will be expecting to have to replace the loom again when the inevitable happens.