1986 GT 1. In the winter (Mid-West winter) the speedo works fine until the engine warms up, then it becomes erratic. It jumps from zero to whatever.
2. Now it starts jumping from the get go. (Now Spring has arrived)
3 . Is there some mysterious sensor involved?
4. Can anyone tell me what's going on with the speedo?
Thanks MrRich
Temperature sensitivity is a good sign of poor contact somewhere in the circuit or a failing Vss. I'd say there's a poor connection that's affected by changes in metal temperature making it better or worse depending on the direction.
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12:08 PM
MrRich Member
Posts: 78 From: Mishawaka, Indiana, USA Registered: Jun 2008
Hope this doesn't sound too ignorent ... what is the Vss refer to? and how do I go about testing it. I don't know where the speedo is connected on the engine or tranny.
Thanks MR
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12:37 PM
My87gt Member
Posts: 142 From: New York, NY Registered: Jul 2003
I suggest you take the cover off the back of your gauge cluster and or better yet remove the gauge pod so you can inspect the contacts from the three wire harnesses that connect to the gauge pod and remove any corrosion with an emery board and some rubbing alcohol.
BE CAREFUL!!! the copper traces on the back of the gauge pods flexible circuit are delicate.
I did this last Sunday on my sons 86GT with great success.. and man the terminals were filthy..
Hope this doesn't sound too ignorent ... what is the Vss refer to? and how do I go about testing it. I don't know where the speedo is connected on the engine or tranny.
Thanks MR
If it is a manual transmission it will be located near the top aft end of the transmission toward the trunkg probably slightly to the right above the inoard CV joint. If it's an automatic it will be at the right end of the transmission just above where the joint inserts into the transmission. The Vss is the sensor that sends the speed signal to the ecm and odometer. Check the plug going into it and examine the wires as best you can.
VSS and VDD are terms that mean positive and negative current or + and -. I suggest you take the cover off the back of your gauge cluster and or better yet remove the gauge pod so you can inspect the contacts from the three wire harnesses that connect to the gauge pod and remove any corrosion with an emery board and some rubbing alcohol.
BE CAREFUL!!! the copper traces on the back of the gauge pods flexible circuit are delicate.
I did this last Sunday on my sons 86GT with great success.. and man the terminals were filthy..
Vss also stands for vehicle speed sensor. I don't know that It's a good idea for him to tamper with the cluster just yet unless he's confident he can do so without a problem for the reason you mentioned since if any of the terminals are separated from the plastic film they can easily be damaged and rendered unserviceable. I don't know for sure but I'd also double check and make sure alcohol is not going to cause any form of corrosive action on the terminals the way it does some types of aluminum. I used brasso to polish them carefully with a dremel tool.
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01:01 PM
MrRich Member
Posts: 78 From: Mishawaka, Indiana, USA Registered: Jun 2008
Just to be clear about this, is it a good idea to start at the instrument cluster or should I start testing in the engine compartment? I don't want to take the pod out if there is another place to check first.
Thanks for the feedback. MR
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01:43 PM
phonedawgz Member
Posts: 17106 From: Green Bay, WI USA Registered: Dec 2009
That's what I'm talking about! The pictures are fantastic, and you have done a service to all. My hat is off to you. Can't wait to start testing. Thank you. MR
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04:20 PM
My87gt Member
Posts: 142 From: New York, NY Registered: Jul 2003
Vss also stands for vehicle speed sensor. I don't know that It's a good idea for him to tamper with the cluster just yet unless he's confident he can do so without a problem for the reason you mentioned since if any of the terminals are separated from the plastic film they can easily be damaged and rendered unserviceable. I don't know for sure but I'd also double check and make sure alcohol is not going to cause any form of corrosive action on the terminals the way it does some types of aluminum. I used brasso to polish them carefully with a dremel tool.
Yeah I had one of those face palm moments. I still stand by my comment before though but by all means check the VSS first.
