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99 legacy speedo intermittent


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Hey all. Wifeys car is having an intermittent speedometer problem. Sometimes it's not working. Then while we're driving sometime later, it'll just start up. Odometer is also out when speedo is out. Most times it works fine, but not always.

Being I'm not familiar with a non-cable activated speedo, what do I look for?

'99 Legacy 2.2 AT, 75K. (Still a young'n)

Thanks.

F4F

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99obw is correct - common failure, it seems on 99 Legacy/Forester/Outback. Search for "speedometer" or "speedometer head" and you see what's been said previously.

 

BUT, having committed all those previous posts to memory, your problem seems a bit different in that the odometer stops working when the speedometer goes dead. To me, that says that your sensor in the transmission case is bad, or there's a short in that line, and it's not necessarily the speedometer head in the instrument cluster.

 

Basic "how it works" for the electronic system, as I understand it: Sensor in transmission case counts how fast the shaft it spinning and sends that signal to your speedometer and your odometer. I *believe* that the speedometer and odometer process the signal in parallel, in other words they don't rely on each other for their information... the odometer uses the raw signal of how many counts per second to determine miles - the speedometer head converts the signal to a voltage and then drives the coil of the speedometer needle to reflect whatever speed that voltage corresponds to.

 

The fact that the speedo and odometer circuits (I believe) are separate leads me to believe your problem is not in the speedometer itself, but from where the signal originates.

 

Quick check is to pound on your dash when the speedo doesn't work. Does it magically start working? Then its probably in the speedo head. If not, then probably somewhere else.

 

-kurt

 

PS - Forgot to add... if you have cruise control, try it out when the speedometer is dead. If it doesn't work when the speedometer is dead, most likely it's the transmission sensor. Otherwise, it points to the speedo head.

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Speedometer and odometer use the same signal. When the head goes the odometer and speedometer will both quit intermittently.

I guess I was assuming the 99 Forester used the same design as the 99 Legacy and Outback. I've got a 99 Forester and have a fussy speedometer. However, when the speedometer is stuck/not working, my odometer still works. Go figure.

 

-kurt

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