Noisy motor has speedometer in a whirr

Hey there, time traveller!
This article was published 28/03/2008 (6567 days ago), so information in it may no longer be current.

QUESTION — I am emailing you, with a question on behalf of my 73 year old Mother. She owns a 1991 Crown Victoria (in excellent condition with 141,000 km) and she has a question regarding a noise which the speedometer makes. This is her question: “In the past 6 months, when driving, at between 40 to 45 KM/H, I can hear a kind of “whirring” sound and when you get past that speed, the noise ceases. I had it at the mechanic for my winter tune-up. He took it for a test run, but did not know why it was making this noise. He said he didn’t think it was serious. Could it be a worn speedometer cable? What can be done to alleviate the noise? Would it be expensive to repair? It really bugs me, and I’d like it fixed. Any information you can help me with is much appreciated.

ANSWER — By 1991, the Crown Victoria, like many other cars, had gone to electronic speedometers and no longer used a speedometer cable. A speed sensor located in the transmission sends an analog voltage signal by wires to the instrument cluster, engine computer and cruise control. The modules then use this data to operate functions or display data, such as speed information.

Inside the speedometer display, an electronic circuit board converts the speed signal into a motor control voltage, which drives an electric motor, which in turn moves the speedometer needle for the dash display. The only moving part of the whole works is the electric motor that moves the speedometer display needle.

The noise you are hearing is most likely coming from the motor in the speedometer display. I have seen many vehicles where this motor would cause a small noise at certain vehicle speeds. The noise isn’t loud or causing a problem, but once a driver “tunes” into this noise, it can be very difficult to ignore it. Sometimes the noise will sound like a “whirring”. Other times, it may be a faint high pitched squeal. As warmer weather arrives, you may find the noise disappears, as different temperatures often change the sound.

To get rid of the noise, the speedometer would need to be replaced or repaired. There are a few specialty shops that repair speedometers if they are removed from the vehicle, but automotive garages only remove and replace the compete unit. They could send them out for repair.

QUESTION — I drive a 2002 Toyota Camry, 4-cylinder. In very cold weather I am unable to get it out of park. If I leave it run for a while it is OK. I suspect that it is an electrical fault as there is quite a bit of electrical failure at the same time. Namely, the heater fan, headlights, dash lights, power windows and there may be other things that do not work. I have a Haynes Manual, which is of no help as there is no information on the shift lever tied in with the electrical system.

I suspect a hung up relay and if you agree would you please tell me the location of the relay. I have looked in the main fuse box under the hood which houses more than a dozen relays. Please name the correct one and its location in the fuse box. Thank you for your assistance.

ANSWER — With so many systems not working, we need to look for something that they all share in common, such as a power supply or a ground connection. I don’t think the problem is with a bad relay, and because these systems are powered by different circuits on the ignition switch, I don’t think the switch is the problem either. That brings us back to power and ground connections.

Check all connections at the main fuse box under the hood. When the vehicle isn’t working, have someone wiggle connections while you try to operate components. It they start working, then look further for bad connections at the fuse box.

Looking at ground connections, all the systems seem to share grounds to the vehicle body behind the driver’s side kick panel. Remove the kick panel and clean and tighten all ground wires. Most of these systems also run circuits through the driver’s side junction box, located behind the left side of the dash. The junction box also has fuses in it. You may have one or more loose connectors at the junction box, so be sure they are plugged in tightly. With so many systems not working, my first bet is on a bad ground connection.

Jim Kerr is an experienced mechanic, instructor of automotive technology and member of the Automobile Journalists’ Association of Canada. You can e-mail questions to Jim at the address below.

kerr.jim@sasktel.net