89 Volvo 740GL Speedometer not working

JohnD · Post by **JohnD** » 15 Jun 2005, 15:47

I have a 89 Volvo 740GL and the speedometer not working. How do I
fix it?

bloonman · Post by **bloonman** » 02 Jul 2005, 19:37

WOW!

I am having this same problem, but with no one responding to your request, I wonder if I need even ask.

John.

LaRy · Post by **LaRy** » 04 Jul 2005, 06:38

The reason you do not get any reply is maybe that it is a complicated problem. The speed sensor in the differential gear is maybe broken or have a bad connetion. This sensor is giving a square wave pulse frequenzy to the speedometer and to check the function you need definitely (minimum) a multimeter that can show Hertz, actually yuo need a scoop meter. If that frequenzy is coming to the speedometer it will go into a electronic converter making the frequenzy to a linjear voltage. That voltage is moving the arrow (finger) in the speedometer showing actual speed. The electronic converter is also needing a stabil voltage supply coming from a voltage stabilisator. This could also be broken, but if the fuel gauge meter is working, this voltage stabilisator is working, because it is using the same voltage.

Most probably the electronic converter in the speedometer is broken and has to be replaced by a new one ore used one. It is a rather wellknown problem that an IC circuit in the electronic converter is getting broken or some electrolyte capacitor is broken by age. The IC circuit problem is so common that in Sweden we have some companies offering an exchange system for the speedometer.

Tomca_ · Post by **Tomca_** » 07 Sep 2006, 05:11

Hello everybody,

just one more question. I also have problems with the speedometer on my 1990 740 GL and also with the fuel gauge. Sometimes they working, but most of the time not (and, of course, odometer also doesn't work, when speedometer is out). As I could see, they do it togeter. However, RPM and temp gauge works fine.

LaRy told, that fuel gauge and speedometer had common voltage stabilizer. My question is, that is this stabilizer also common with temp gauge or not. So, could the stabilizer be also my problem, or I have something else?

Thank you for the answers in advance,

Tamas

LaRy · Post by **LaRy** » 07 Sep 2006, 12:58

I have now made some investigations and have to correct myself. According to what I can see in the electric diagram the voltage stabilizator is giving power to the temp gauge meter and the fuel gauge meter, nothing more.

sjh · Post by **sjh** » 04 Nov 2009, 13:13

I have been dealing with no speedometer on my 1991 740 for almost 2 years now. I finally got up some ambition and decided to look at the speed sensor on the differential. I had looked at it before and noticed that the wires that exited the connector were stripped and exposed from general wear. I thought this might be the problem and wrapped them in electrical tape to keep them separated. This did not help. Next I pulled the connector out entirely and realized that the wires had actually broken inside the connector rubber boots. I removed the boots from the connector ends, spliced the female connections back onto the wires then re-attached the connections to the sensor. Everything works great now! I just wish I had looked into it deeper 2 years ago.

Maybe this will help you or someone else.

SJH

Post by **billofdurham** » 04 Nov 2009, 15:32

Thank you for this. It is a fairly common fault often overlooked. Those wires are at the mercy of the elements every time you take the car out.

Bill.

dambergw · Post by **dambergw** » 29 Apr 2011, 10:34

Hi,

I have a 1989 Volvo 740 GL and the speedomoter only works when i hit the dashboard? Could this be a lose connection in the back or a problem with the printed circut board?

Thanks
Will

Post by **billofdurham** » 29 Apr 2011, 11:41

Welcome to Matthew's Volvo Site.

740 speedos do suffer from bad connections on the circuit board. This is covered here and may provide a solution

Bill.