Speedometer problem

[Camillus]

The speedometer on my 1986 Volvo 744 (66300miles) is sometimes reading okay and other times it just drops back to zero. It's flickering between giving a reading and no reading. I checked the 2 wires at the sensor (differential) and found them to be okay. Contacts very clean. No loose wires. I ran a separate earth wire from the brown(chassis) wire at the sensor to the frame. Then took out the instrument cluster and cleaned the 3 contacts that the speedometer plug goes into. Tightened all screws. Still no luck. Continuity good between plug (instrument cluster) and sensor wire (green/white). Put multimeter across the 2 pins on the sensor but got no reading on the ohm scale (open circuit.?) Why is the speedo. only working sometimes.?? Anyone out there have a similar problem.? Any advice or help would be greatly appreciated.

[Forrest]

You will need to trace where exactly the fault is. Likely places are the sensor in the rear differential, the cabling to the sensor, dry joints on the instrument cluster PCB or the instrument itself. In the case of the latter this link may be of assistance. It also includes some handy diagnostic tips.

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

[bob12]

I am assuming you have a VDO cluster. 66K is about right for a VDO to start playing up!! Is your mileometer and trip odo still working, or do they stop when the speedo needle stops working?? Bob

[Laird Scooby]

Have you got ABS on the car? If so, does the ABS light come on when the speedo dies?

[bob12]

Originally Posted by Laird Scooby

Have you got ABS on the car? If so, does the ABS light come on when the speedo dies?

ABS unlikely on an '86 saloon, but who knows. Bob

[Ian21401]

Hello Camillus,
Suggest, instead of simply checking the tightness of those screws on the PCB, remove them in turn and clean the PCB beneath them with some none metallic and none dusty abrasive. eg a glass fibre tip pencil.
Was there any sign of the capacitors leaking and damaging the PCB?
Do a search on this section using parameter “Speedometer Fault”.
Have a look at my old threads, “Intermittent Speedo/Odometer Fault” and
“Help Please re Speedometer Fault”, especially the link to “ brickboard” in the latter thread.
Good luck.

Ian.

Sorry, but I don’t know how to do that “show thread” linky stuff. Maybe someone will describe how?

[Laird Scooby]

Originally Posted by Ian21401

Hello Camillus,
Suggest, instead of simply checking the tightness of those screws on the PCB, remove them in turn and clean the PCB beneath them with some none metallic and none dusty abrasive. eg a glass fibre tip pencil.
Was there any sign of the capacitors leaking and damaging the PCB?
Do a search on this section using parameter “Speedometer Fault”.
Have a look at my old threads, “Intermittent Speedo/Odometer Fault” and
“Help Please re Speedometer Fault”, especially the link to “ brickboard” in the latter thread.
Good luck.

Ian.

Sorry, but I don’t know how to do that “show thread” linky stuff. Maybe someone will describe how?

Are you familiar with "Tabbed Browsing" Ian? It's the process of having multiple browser tabs open each with different web addresses so you can switch between for example, email, ebay, this forum and whatever else you visit regularly at the same time. The top of the browser screen will have tabs across the screen, each with the name (sometimes shortened) of the site on that tab, a bit like the card index systems from way back when. Simply left click on the tab to view that page.

There are several ways to open a new tab, many browsers have a "+" sign where the new tab will open, click that and a new tab will open for you, effectively giving you a blank browser page to either type the web address you want or click one of your shortcuts.

A second method is if you use a mouse with a clickable scroll wheel, simply click the wheel and a new tab opens.

Thirdly, CTRL and T pressed together will open a new tab.

There are other methods such as right-clicking a link in a thread and then click "Open link in new tab".

Now you have your tabbed browsing in operation, doing the "show thread linky thing" is fairly easy.

In the post you are creating and want to add the link to, you will have decided where you want that link to appear. Usually the cursor will be at that point anyway as it flows easier when typing etc.

Click on the tab of the thread you want to link to so your view switches to that tab. Now move the cursor to the address bar near the top of the screen. Right click in there and the web address is highlighted and a small menu appears, one of the options is "Copy".

Now go back to the post you're making and click where you want the link to appear. Now right-click and select "Paste" from the options that appear.

Press "Return/Enter" on your keyboard, i like to press it twice to give a space of one complte line between things like links, photos etc before the following text. Then carry on typing with whatever else you need to add.

I hope that makes sense, i'm a total doofus with software so the explanation may not be "text-book perfect" but hopefully you can follow it!

[bob12]

Originally Posted by Ian21401

Hello Camillus,
Suggest, .......................
Good luck.

Ian.

Sorry, but I don’t know how to do that “show thread” linky stuff. Maybe someone will describe how?

Depends slightly what system you use. Basically though 'open' the particular thread on the VOC Forum you want to include in a post. The full 'IP' address of the page will appear in the top bar. Highlight the FULL address 'right click' and 'copy' it. Then in your thread right click and 'paste' it and the link will appear there so that when you have sent your 'reply' it will be possible for others to click on it to open it. Hopefully like this page: https://www.volvoforums.org.uk/forumdisplay.php?f=14

I think that what we now need is a reply from Camillus to firstly let us know what oem cluster he has. I have a gut feeling that it will be a VDO which has different problems to the Yazaki.

Cheers, Bob

[bob12]

For the VDO speedo I found this page on Dave Barton's relatively new 240 Turbo site (since Volvo America upset him) quite helpful for a VDO speedo: https://www.240turbo.com/740-odometer-repair.html

Bob

[Laird Scooby]

Ian - what Bob said above about adding the links is more or less the same as what i said, just in a more concise form and different language. Whichever is easiest for you to follow will likely be most helpful for you!

Definitely need to hear back from the OP - beginning to feel like a mushroom here!