740 speedometer needle setting after fix

[bob12]

Glad it now seems to be fixed and working OK ... Bob

P.S - forgot to ask, out of interest did the speedo have the later 5 thin pin connectors off the pcb to the backboard or the flat tags forming part of the pcb board?

[Laird Scooby]

Errr, yeah...............what Bob said! ^^^^^^^

[Hell Driver]

Originally Posted by bob12

Glad it now seems to be fixed and working OK ... Bob

P.S - forgot to ask, out of interest did the speedo have the later 5 thin pin connectors off the pcb to the backboard or the flat tags forming part of the pcb board?

Would that be the thin pins in a row you have to be careful to line up with the sockets when you place the speedo in position ready to screw back on?

[bob12]

Originally Posted by Hell Driver

Would that be the thin pins in a row you have to be careful to line up with the sockets when you place the speedo in position ready to screw back on?

Yes, that's them the five thin pins that bend easily if you don't line the up centrally with the female part on the backboard. It's the cause of a speedo 'apparent fault' as one or the other can slip to one side of the connector and not make any electrical contact.

[Hell Driver]

Yes. it is that type with the pins then. So far so good, done a bit of driving and everything works OK, even changed the blown bulbs at last so all the back lights working now. Some of the other dash lights were blown too. A small detail that left me stranded on the M1 a couple of years ago...battery charging light bulb had blown so I didn't get warning that the alternator brushes were worn away

[Laird Scooby]

Originally Posted by Hell Driver

A small detail that left me stranded on the M1 a couple of years ago...battery charging light bulb had blown so I didn't get warning that the alternator brushes were worn away

Unless you're in the habit of checking your warning lights when you first switch the ignition on, you wouldn't have known anyway. The moment the charge warning light doesn't illuminate with just the ignition on, you know you've got a problem.

[bob12]

Originally Posted by Hell Driver

Hopefully final update! Looks like friction was the problem. Yes, the collar should be upwards as per diagram. I've returned it to that position (in which it wasn't working when I first reassembled) and added a tiny amount of oil to every moving cog/friction surface. (But not the digits!) ..................

Sorry to resurrect this post, but I forgot to ask and interested to know exactly what sort of oil you used on the stepping motor plastic gearing. Fine machine, silicone or... ?

Cheers, Bob

[Hell Driver]

It was just a general household lubrication oil. Hope it doesn't affect the plastic! Wasn't it the oil that damaged the original cog that they made out of the wrong plastic or something? Still working OK. I just put a tiny amount on.

[bob12]

Originally Posted by Hell Driver

It was just a general household lubrication oil. Hope it doesn't affect the plastic! Wasn't it the oil that damaged the original cog that they made out of the wrong plastic or something? Still working OK. I just put a tiny amount on.

Thanks very much for that 'Hell' , and glad to know you fixed it. Who is really worried as long as it's working OK!

It's good to know what you used as I have never used any lubricant when replacing the errant gear wheel on a VDO speedo as I have never seen any sign of lubricant on the gears (or residue) when the speedo is taken to pieces .... just one or two sheared teeth.

In my opinion the cause of failure of the particular gear wheel is a combination of age degradation of the 'plastic', or whatever the gearwheel was made of, and mechanical abuse as a result of zeroing the trip odo whilst on the move.

Like you I have had problems with getting the speedo/odo to work efficiently after replacing a gear. It's a bugxer!

The best VDO speedo which I now have in my cluster on the 745 is one made by VDO Australia that I acquired in a 740 cluster I 'happened' pick up. I won't elaborate, but it's age indicates it was a replacement for a German made one at a time when VDO were in financial 'difficulties'!!!

Thanks again - Bob