AT TEMP, speedometer drops, engine jerks

[handybob]

My wife has a 1999 Legacy Wagon, 4-cyl. with 80K. When it has been driven at least 15 minutes, within a period of no more than a half second, the speedometer and tachometer needles will drop to zero and return to their original setting, the AT TEMP light will come on and the car will jerk as if it momentarily shifted or tried to shift gears. It returns to normal (light goes off), but will continue repeat the above on a random basis from a few seconds apart to a few minutes apart.

 

If you shift to third, the light blinks on and the speedometer drops, but the tach doesn't move and the car does not jerk. If you are running cruise control and it does the above, it unset cruise control.

 

We've had the fluid changed and wiring harness/speed sensors replaced by dealer with no change. He says the computer is setting no code. He wants to rebuild transmission but can’t guarantee a fix.

 

Did some research on my own and discovered Tech bulletin 1199-02 which said complaints of speedometer needle jumping, dash warning lights on or glowing dimly and driveability problems, are probably the alternator. Suggested disconnecting alternator as a test. If problem goes away then alternator is the problem. I disconnected it and problem did not go away. Curiously, the light on the dash to indicate the battery was getting no charge did not come on.

 

Car had 12,000 miles on it when we purchased. Have had no other problems. Any ideas?

[friendly_jacek]

My wife has a 1999 Legacy Wagon, 4-cyl. with 80K. When it has been driven at least 15 minutes, within a period of no more than a half second, the speedometer and tachometer needles will drop to zero and return to their original setting, the AT TEMP light will come on and the car will jerk as if it momentarily shifted or tried to shift gears. It returns to normal (light goes off), but will continue repeat the above on a random basis from a few seconds apart to a few minutes apart.

 

If you shift to third, the light blinks on and the speedometer drops, but the tach doesn't move and the car does not jerk. If you are running cruise control and it does the above, it unset cruise control.

 

We've had the fluid changed and wiring harness/speed sensors replaced by dealer with no change. He says the computer is setting no code. He wants to rebuild transmission but can’t guarantee a fix.

 

Did some research on my own and discovered Tech bulletin 1199-02 which said complaints of speedometer needle jumping, dash warning lights on or glowing dimly and driveability problems, are probably the alternator. Suggested disconnecting alternator as a test. If problem goes away then alternator is the problem. I disconnected it and problem did not go away. Curiously, the light on the dash to indicate the battery was getting no charge did not come on.

 

Car had 12,000 miles on it when we purchased. Have had no other problems. Any ideas?

Problems with ground connection?

Intermittent electic connection?

ECU/TCU going crazy?

Problems with one of the sensors?

Sounds like you need to take matters in your own hands. I guess the dealer is trying to rip you of.

[Tiny Clark]

Have your alternator tested at Autozone under load conditions. Seems like I had similar problems when my alternator went tango uniform.

 

Used to be, in the old days, you could run a car for days on a fully charged battery. With everything being electrified now, you probably wouldn't get an hour down the road.

[rallyruss]

it may sound stupid but how old is the battery? how are the connections? and dont run the car straight off the battery or alt. have the batt tested.