Electrics: 70: Spinning key syndrome - method to fix

[SwedishBus]

There are two stages to making this mod; the first is that a "grub screw" needs to be fabricated to lock the anti-force dog permanently to the inner shaft;

V70_modified_anti_force_dog.jpg

I used an M5 x 0.8mm metric-course tap, in order to thread the existing sliding-pin hole. The hole itself is just the right size to tap from, although I did use a set of three taps to make this thread (first tap to begin the threading process, with a heavy taper, all the way through to a plug-tap). With care and a bit of cutting-oil, a final plug tap could be persuaded to go into the sliding-pin hole, I reckon.

The "grub screw" is a long M5 x 0.8mm screw, cleaned in solvents, and with its tip ground to a conical form. I ground a fillet of around 15degrees from the face of the end of the screw, just enough to allow the screw to wind deeply into the existing slot in the tumbler centre shaft - as the sliding pin would have achieved in normal use. The sliding pin itself is now no longer required: It is shown in the photo for comparison to the tapped hole only.

Before the modified anti-force dog can be fitted, the region of the side of the tumbler outer casing (as indicated in an earlier photo/post) needs to be cut-away with a Dremel, or similar, then dressed clean with a needle-file on the inside of the cut near where the "ramp" feature for the sliding-pin would have been - this is just to ensure nothing snags in service.

V70_modified_tumbler_barrel.jpg

Having dry-assembled and tried this modification, I re-cleaned the screw thread, applied some Loctite Studlock to the first 5 threads, then wound it in with the anti-force dog in-situ, ensuring that it was all locked wrist-tight before leaving everything to set for a few minutes.After this, the rest of the screw was cut-off with the Dremel cutting-disc, as close as possible to the dog face as I could get. Once the bulk of the screw was removed, I used the cutting disc to gently grind the remainder of the protruding screw flush to the dog-face (I know, I know, you should never use a cutting disc as a grinder, but meanwhile, in the real world..........). I refitted the circlip to the end of the tumbler inner shaft, just for completeness. It isn't 100% necessary, but just in-case the "grub screw" works slightly loose, it would be good to know that the dog-drive cannot slide upwards on the shaft.

A quick blow-down with the air line, followed by a trial run with the key in the tumbler-assembly, proved that it would all turn without snagging. At this point, I was able to wash the whole tumbler assembly in brake & clutch solvents again, blow the whole lot dry, then lubricate with a "dry PTFE" spray up through the key-slot.

At this stage, the spinning-key-syndrome should be fixed, but to ensure that the key barrel assembly never gives trouble again, I did some "belt & braces" modifications to the rest of the lock mechanism.

[SwedishBus]

The centre shaft that transmits the tumbler motion, via the anti-force dog, to the rest of the barrel mechanism has three separate jobs;

V70_barrel_camshaft.jpg

The main purpose is to turn the electrical switch via a small feature at the end of it "A". In the specific case of my car, the switch was not behaving very well at all, and I suspected that it had been the cause of a few "crank, no-start" problems that my wife had experienced a few months ago; she had been stranded for a short while in each case, and had lost a fair bit of faith in this car........The main fault symptom was an imobilisation code, and my prognosis had been that the various circuits supplied by this switch had not been switched-on correctly and in the right order. Therefore I had already pre-purchased a new switch (Skandix) which is a genuine Volvo part, and this can be fitted once the barrel assembly is back on the steering column;

V70_new_switch.jpg

The secondary purpose of the camshaft is to lift the steering lock pawl (casting & peg assembly) via the cam at "B", and this is one of the biggest torques that the tumbler must overcome. I made the decision to remove this pawl as a complete assembly, to obviate any further issues with the anti-force drive-dog. This will imply that the steering will no longer lock, and that may be an issue in the UK for the annual MoT (technically this is a tested item, but I have never seen the purpose of it......), however it is possible to rebuild the removed components back into the barrel casting at some later date - I kept the small bits in a labelled bag.

To remove the pawl, a sprung pin needs to be depressed through the end of the barrel;

V70_stg_lock_pawl.jpg

which can also be seen down through the steering-lock aperture;

V70_stg_lock_pawl#2.jpg

In any case, it might be worth removing the pawl to confirm that a small rectangular bit of the pawl die-casting is not loose and floating-around in the housing around the pawl - it seems to be snapped-off in every video I have seen. Given the risk of this jamming the pawl, it would make sense to empty it out of the barrel. I have no idea what it achieves when it is a contiguous part of the casting!

The third, and final, part of the cam "C" is the auto-transmission parking-cable, which is not present on my car (a manual), but may be a source of more problems if the transmission is allowed to jam the action of the tumbler-mechanism. I reinstated the plastic keeper on my lock-barrel, to ensure that nothing could lodge in there, but modified that keeper to obviate any chance it could act to jam the camshaft, by shortening it at a point before it abutted the camshaft. There may be some opportunities to improve the "P" interlock function/adjustment on auto-trans cars.

Once all these mods have been made, reassembly is very simply the reverse of disassembly. Everything is uniquely timed to its neighbour, so it is very difficult to get things misaligned. The electrical switch can go back into the end of the barrel in two orientations at 180degs from each other, but the harness-connector on the car will dictate which way round it goes, which is obvious when the switch is fitted (as-per the photo above).

The fixes mentioned so-far have been tested for a few days, and the whole action of the key-barrel is transformed - the car has never felt better, nor the electrics ever switched so cleanly on turning the key. It now feels 100% reliable, so we will have to see what the wife thinks!