700 series Odometer problem:

[90Wine745]

This is more for newbies like me than other seasoned users. Very satisfied that I managed to fix the broken odometer on my 1990 745. Again, many thanks to all the info from the forum, without, I had no clue where to go, in this post I tried to bring a few of the bits together.

If your odometer is not working and your speedo is, most likely it is a broken little cog wheel in the back there somewhere.
Which Speedometer: YAZAKI or VDO? Yazaki has spaces between the trip numbers, VDO does not, tenth of the mile is separate though and usually white background. (See links below.) Make sure you know which one you have. Mine was a VDO.

Part and process I used is attached. Also a really great video on u tube, two guys with an orange dashboard. I have no idea what they are saying but, for me, I did not need to. English sub titles at critical points. Also great pics on DaveBarton.com Cannot stress enough to be careful with the speed needle removal. One thing I would add is that you should separate the screws as you take them out so that you put the right ones back in the right places. They are different sizes and they are are part of the circuits rather than just holding the thing in place.
You need to be very careful, but really, just take your time and it will be easy.

This is the part I used:
https://www.partsforvolvosonline.com...ducts_id=10240

Process I Followed:
http://www.volvotips.com/index.php/7...740-tripmeter/


Other Links:

Volvo Owners Club Forum > "Technical Topics" > 700/900 Series General > 740 Speedo/Odometer Failure??

https://www.volvoforums.org.uk/showt...er+Replacement

https://www.volvoclub.org.uk/faq/Ele...eterRepair.htm

https://volvoforums.com/forum/volvo-...working-81641/

There are loads more info on the forum and also any search on internet for 740 Odometer repair/replacement will get you off to the good start.

Enjoy.
Mike

[bob12]

Glad you got it fixed OK. Yes, with patience it is quite an easy job.

I would comment on just one point you make in that (some) screws are part of the circuits rather than just holding the thing in place.

As far as I am aware having fixed several VDO Odo's none of the speedo unit holding screws form part of an electrical circuit.

Well done,

Bob

[90Wine745]

Originally Posted by bob12

Glad you got it fixed OK. Yes, with patience it is quite an easy job.

I would comment on just one point you make in that (some) screws are part of the circuits rather than just holding the thing in place.

As far as I am aware having fixed several VDO Odo's none of the speedo unit holding screws form part of an electrical circuit.

Well done,

Bob

Oh! Sorry for the bad information. Thank you for the correction.
It is so good to get it working again.
Take Care,
Mike

[Laird Scooby]

Originally Posted by bob12

Glad you got it fixed OK. Yes, with patience it is quite an easy job.

I would comment on just one point you make in that (some) screws are part of the circuits rather than just holding the thing in place.

As far as I am aware having fixed several VDO Odo's none of the speedo unit holding screws form part of an electrical circuit.

Well done,

Bob

Originally Posted by 90Wine745

Oh! Sorry for the bad information. Thank you for the correction.
It is so good to get it working again.
Take Care,
Mike

You're both right as it goes. It's cluster-dependent, on my 1988 Yazaki cluster, the screw with the ring crimp attached actually passes the speed signal from the PCB on the back to the speedo :



Two others pass the +12V and 0V into it as well as holding it in place. Ditto on the fuel gauge, +12V, )v and signal. Dry joints on the PCB are plentiful sadly. Worth looking at if your fuel gauge isn't working!



Those joints at the end of the dashed lines were all dry and preventing my fuel gauge working - desoldered, fluxed, resoldered (with fresh 60/40 tin/lead solder - the proper stuff) and cleaned with IPA and i have a working fuel gauge.

Great work on your speedo Mike!

[90Wine745]

Originally Posted by Laird Scooby

You're both right as it goes. It's cluster-dependent, on my 1988 Yazaki cluster, the screw with the ring crimp attached actually passes the speed signal from the PCB on the back to the speedo :



Two others pass the +12V and 0V into it as well as holding it in place. Ditto on the fuel gauge, +12V, )v and signal. Dry joints on the PCB are plentiful sadly. Worth looking at if your fuel gauge isn't working!



Those joints at the end of the dashed lines were all dry and preventing my fuel gauge working - desoldered, fluxed, resoldered (with fresh 60/40 tin/lead solder - the proper stuff) and cleaned with IPA and i have a working fuel gauge.

Great work on your speedo Mike!

Thanks Dave,
Yes, I have a dodgy fuel gauge. I must have a better look at mine again just as soon as I get a chance. Was thinking of investigating it so I will start here.
Take Care,
Mike

[bob12]

Thanks Dave. That maybe so for a Yazaki but it doesn't apply to a VDO.

The four holding screws on a VDO screw in via the blue plastic circuitry into the plastic frame of the speedo unit. There is absolutely no electrical connection involved with the holding screws and the blue plastic circuitry although they can be utilised for separate purposes such as 12V + and - as I have used them to feed a voltmeter. At first glance it might look like there is a connection but there isn't.

The speedo unit itself on a VDO is fed and output'ed from the blue plastic circuitry via contacts either 4 flat tabs or 5 thin pins (depending on age) off the speedo pcb at a connector housed to the left of the speedo in the raised plastic section of the backboard as shown in the attached picture.

As to a dodgy bonkers VDO fuel gauge the fault is usually associated with a bad solder connection in the pcb at the back of the fuel gauge itself rather than any other cause of which there are several.

Bob

[Laird Scooby]

Like i said Bob, it's cluster-dependent. In other words, they could be (and from what you tell and show me are) different, each needs to be approached for what it is.

I seem to recall from when i made a new fuel gauge for my last 740 that i picked up the feeds from the screws that held the gauge in.



Long time ago now (8 years) so entirely reasonable i've remembered something incorrectly - it was a one-off after all!

[bob12]

I would need to refresh my mind on the fuel gauge connection. I will have to look at one when I venture into the garage to get the mower out this afternoon. The weather down here is knocking 23C.

[bob12]

Got the mower out but it's too xxxx hot to cut the grass at the moment so I will leave it for an hour or so.

Meantime, I have looked at both a VDO and a Yazaki fuel gauge to refresh my failing mind.

The VDO fuel gauge is held in with one nut screwed on to the backboard with all electrical connection solely via 3 thin pins off the fuel gauge pcb that connect to a socket attached to the back board. The pcb of the gauge I looked at seemed to have been fairly toasted at it top half with melted lacquer and I had put a note on it that it only read full!!

See attached pic. showing the nut and the back of the 3 way connector off the blue plastic circuitry. The nut has no electrical connection as it is insulated by the white backboard from the pole on the fuel gauge pcb to which it is attached.

I also looked at an old Yazaki that I had. That has a totally different way of connection. As you say Dave it is via the holding nuts that attach it to terminals on the backboard circuit.

Bob

[bob12]

Forgot to attach the picture!!!!

Bob