Question about 1991 Volvo 740
OK. We'll take this step by step.
1) two possibilites: One is the speedometer itself. The other is the vehicle speed sensor in the differential cover near the top of the housing. Of course, check all fuses inside the electrical distribution unit.
2) Speed sensor and its wiring can get knackered over time, so carefully go over the wiring from the speed sensor at the rear of the vehicle all the way to the engine bay. It is simply two 18 gauge wires in a sheath. If the wiring is OK, the sensor could be faulty. To change it involves using a clamp-type pliar on the nut. Do not over tighten it, you can crush the nut and it will be impossible to remove it without removing the differential cover and potentially the entire carrier as well. It simply unscrews from the differential, it is around 30 dollars at fcpGroton.
3) If that all looked good, possibly the speedometer itself is faulty. Replacement isn't too bad. I did several of them. Yes, the original can be repaired, usually it is a small plastic gear inside the unit itself, however the speedometer itself should still work even if the gear is broken. My guess is that the sensor is faulty, the connection on the back of the cluster is faulty, or the wiring is faulty, so go over that first (no money, just time) carefully.
4) To remove the cluster, insert a small flat-bladed screwdriver under the two plastic covers (one goes over the hole for the clock adjustment) and pry them off. Remove the two screws that hold the cluster in place. Carefully lift out the cluster from the dashboard, guiding out the wiring harnesses along the way. The wiring harness that does the speedometer is located in the center of the cluster with a white locking collar around it. Check that one for security and cleanliness. To remove the cluster entirely, separate the various harnesses and connections, noting how they are connected (take a picture of it first) and then guide the cluster out. Do not drop or jar it, it is fragile.
5) From here I usually start by using a pencil eraser on the copper connections and then gently buffing them out. The pencil eraser removes the oxidation without abrading the copper etch; the buffing removes the pencil eraser fragments. I change old bulbs, clean up the unit and reinstall. If you are sure the speedometer is knackered it can be removed after removing the front bezel fixing screws and all other attachments. It separates from the unit from there.
6) When you install, ensure the speedometer connections are clean and tight and the locking collar is in place.
7) Test. Usually, this resolves this annoying little issue. Unless the sensor is bad, you should be golden. -AS
Posted on Jan 28, 2011
a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of.(from cars to computers, handyman, and even drones)
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jan 02, 2011 | 1991 Volvo 740
Nov 15, 2010 | 1991 Volvo 940
Apr 03, 2010 | 1995 Volvo 850
Sep 24, 2009 | 1991 Volvo 740
Sep 24, 2009 | 1988 Volvo 740
Dec 11, 2008 | 1994 Volvo 940
Jun 26, 2008 | 1991 Volvo 740
759 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: