How to repair the 740 odo- & tripmeter
A very common problem for the Volvo 740 (and also 760, 780 and 900-series) is the tripmeter and odometer (or: mileage indicator) which stops working. If the speedometer is still working the problem is in most cases very simple: inside the instruments unit there is a very small cogwheel which is made of nylon. Sooner or later a small tooth (or even several teeth) will break and the tripmeter will stop working, resulting the odometer to stop working. But with this step-by-step tutorial it’s very easy to fix this problem!
How to get the right cogwheel for your Volvo 740
Volvo used two brands for their analog milometer/speedometer-instrument: VDO and Yazaki. It isn’t hard to recognise it: the VDO doesn’t have the “splitted numbers” at its tripmeter. The numbers of the Yazaki are seperated as you can see on the picture below.
Now you’ll know if you have a Yazaki or VDO-unit in your car, but the cogwheels can vary due the number of teeth on the cogwheel. When you remove the speedometer instrument of the instruments unit a number is visible (also some numbers on the back) which help to order the right cogwheel for your car. If you insert the wrong cogwheel the unit will give incorrect values of the distances so the tripmeter will turn too fast or slow and the mileage will be wrong. The removal of the instrument is described below.
Requirements for the cogwheel-replacement:
- a new cogwheel (sold at Erich Technical Support, IPD, your local Volvo-dealer and other webshops)
- a small flat screwdriver
- a Philips screwdriver
- not neccessary: a knife or nipper to cut the tie-wraps of the cable harnesses which are connected to the instrument cluster
- not neccessary: glue to fix the needle of the speedometer if it’s get damaged at the removal.
How to repair your odometer and tripmeter of your Volvo 740 or 760/780
With this guide you can easily repair your broken tripmeter and odo/milometer. Just follow the steps below and it’s a piece of cake!
This tutorial is written for the Volvo 700-series until 1991 (since MY91 the dashboard is changed to the version of the 760/940-series), a how-to for taking the dashboard of these late types will appear soon.
If you want to be sure not damaging any electrical components please disconnect the negative battery cable.
Click on the pictures for a larger version (will open in a new tab/window).
Step 1: remove the small covers with a flat screwdriver (or knife)
Step 2: unscrew the Philips screws
Step 3: removing the instrument cluster
Please note: put the turn signal and wiper stalks down to remove the instrument cluster. Now you can pull the instrument cluster away from the dashboard.
Step 4: remove the connectors at the back of the instruments unit
Remove the connectors at the back of the unit. Please keep in mind which cable is connected on which place. If the cable harnesses won’t come out a lot you can cut the tie-rips between the cable harnesses to provide more space and remove the unit easier. In most cases there is a plastic clip which operates as a seal at the speedometer connector. You’ll need to remove it before the connector can be peeled off.
Step 5: dismantling the instruments unit
It’s time for the hard work now: taking apart the instrument cluster. But I’ve made an image with which screws should be taken out to open the unit.
After you removed all the screws remove the clock adjuster. Now you can remove the white backpart of the unit away from the black front. Please be carefull and don’t damage the instruments and pins.
Take out the speedometer gauge very carefull.
Note: nouw you can see a number in the low right corner of the dial. That number will help you ordering the right Volvo cogwheel for the odometer and tripmeter. There are also a couple of numbers on the back of the gauge which might be needed for ordering the cogwheel.
Step 6: disassembling the speedometer gauge
Now it’s time to disassemble the speedometer instrument, so we can get to the odometer gear.
Removing the speeding needle is pretty difficult. If you use two screwdrivers you can pull away the needle but please put some fabric or small cardboard-pieces to prevent damage on the dial cover. Some people prefer to take out the round center of the needle, but in that case you’ll need to glue the center back when putting the speedometer back together.
Now pull away the dial sticker and three screws will appear.
To seperate the mechanical part and housing you’ll need to remove the 3 small screws. Use a flat screwdriver to remove them.
Step 7: replacing the cogwheel
The cogwheel is located on the right side of the unit. As you can see on the picture above and below there is a PCB with several electronic components on the right side. Below these parts the cogwheel can be found. You’ll need to remove two screws (see below) to remove these components. Please be carefull: the electronic wires may not be damaged or removed!
Now remove the broken cogwheel and replace it with the new one.
Step 8: reinstall all parts and put it back together!
To finish the repair please do all steps above backwards (except installing the broken cogwheel of course) and enjoy a working trip- and odometer! And don’t forget to set the right time on the clock.
If you wish you can also replace some lights. It’s pretty easy and a cheap fix. The right lamps can be bought at your local car parts store, the Volvo-dealer or any webshop.
Other common problems of the Volvo 700 speedometer
If your odometer and tripmeter doesn’t work but your speedometer does work fine the problem is in almost every case a broken cogwheel. Sometimes the little electronic driver which is above the cogwheel is broken but it’s pretty rare.
If your speedometer also doesn’t work the problem can be found at the rear axle and driveshaft: a sensor is installed to calculate rotations which delivers the right speed and distance for the speedometer and odometer. But sometimes the cable and connector at this sensor is broken. You can clean it (solves the problem in most cases), repair it or replace the connector and/or cable (also very common) but sometimes the problem can be caused on the gauges unit itself: corrossion or a bad solder can damage contacts and capacitors or other components like the UAF2115 chip. A visual inspection will find the cause in most cases.
If you have any questions, please feel free to e-mail me on firstname.lastname@example.org!
© Volvotips 2012