Speedometer goes off during hot weather only 96' 850

DWNiefer · Post by **DWNiefer** » 22 May 2007, 17:33

During hot/summer time or on heavy traffic during warm/hot weather, speedometer goes off unexpectly.. Either stopped to cool off or on normal highway during cooler weather, it goes on as normal.. Though several mechanic tried to fix or I replaced some sensors, problem is still there.. sigh.. Anyone has same problem as mine? If so, kindly please tell how to fix it darn up..

silver99s70 · Post by **silver99s70** » 22 May 2007, 23:35

Hi DWN,
You don't mention any other symptoms / warning lights, so my info may not apply. All I can tell you is that all of my electronic and engine freak-outs, including displays going blank, went away after two things were done. I got the ETM replaced (with the software upgrade)- under the extended warranty, and, I replaced the ABS module. At times my erratic operation seemed tied to heat build-up as well. It certainly is possible that a marginal electronic component or circuit could short out or malfunction when it gets to a certain temperature. At some point it should fail completely, however, and not function normal after cooling down.

I believe your '96 was before the ETM headaches, but if you had any issues with ABS, maybe there's something to investigate there.

Good luck.

DWNiefer · Post by **DWNiefer** » 23 May 2007, 09:17

Well, SRS light is still on but it started on right after I replaced front side passenger seatbelt so I thought it doesn't related but who knows.. When I bought my car few years ago through foreign used/new dealer/friend, "check engine" lights came on few times and same time speedometer went down.. He tired to fix... only lights go off for good but still problem w/speedometer.. Different mechanic tried to fix but no avail.. sigh.. Speedometer problems only during hot weather.. other than that all is well... hummm.. thanks for respond and appreicated!

DWNiefer · Post by **DWNiefer** » 23 May 2007, 09:18

Well, SRS light is still on but it started on right after I replaced front side passenger seatbelt so I thought it doesn't related but who knows.. When I bought my car few years ago through foreign used/new dealer/friend, "check engine" lights came on few times and same time speedometer went down.. He tired to fix... only lights go off for good but still problem w/speedometer.. Different mechanic tried to fix but no avail.. sigh.. Speedometer problems only during hot weather.. other than that all is well... hummm.. thanks for respond and appreicated!

silver99s70 · Post by **silver99s70** » 23 May 2007, 22:23

Hi DWN,
Have you or your mechanic checked OBDII codes ? If the control system is flagging that something is wrong/not working, that may give you something to go after. You could follow up on that SRS warning also- at least try to find out exactly why it's on, so you can eliminate that variable from your troubleshooting.

Good luck

Post by **Ozark Lee** » 24 May 2007, 07:05

Well, SRS light is still on but it started on right after I replaced front side passenger seatbelt so I thought it doesn't related but who knows.. When I bought my car few years ago through foreign used/new dealer/friend, "check engine" lights came on few times and same time speedometer went down.. He tired to fix... only lights go off for good but still problem w/speedometer.. Different mechanic tried to fix but no avail.. sigh.. Speedometer problems only during hot weather.. other than that all is well... hummm.. thanks for respond and appreicated!

As far as your SRS goes , you will just need to get the dealer to reset the alarm for you. In the future, never mess with the seat belts or any of the other airbags, including the seats, without first disconnecting the battery and then waiting a few minutes before you jump in.

The speedometer issue is becoming clearer now that we find that the CEL is coming on at the same time that the speedometer fails. I'm leaning towards a faulty Vehicle Speed Sensor. They are normally not temperature sensitive but they are an electronic device and if it is on the edge of tolerance temperature can certainly push it over the edge.

An interesting experiment would be to try to use the cruise control while the speedometer is in a failure mode. If it does not work I would change the VSS sensor. It is located more or less halfway between the half shafts on the bottom/rear of the transmission and it is fairly easy to change.

...Lee

dykaar · Post by **dykaar** » 25 May 2007, 07:36

BTDT. I had the dealer replace the sensor, but kept the old one. Sure enough same problem. I had them put the old one back and ran a new set of wires from the sensor to the dash. Get used to it. These cars are where old Lucas (the prince of darkness) electrics go to die. I also have an intermittant on the coolant gauge and outside temperature gauge, so I'm thinking there is either a bad ground, a crimped cable, or more bad electrical connections (at the connector), just like the seat heater thermostat...