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Speedometer jumping. Is speedo dying? by Boostdreamer
Started on: 01-21-2014 11:10 AM
Replies: 20 (769 views)
Last post by: Boostdreamer on 02-08-2014 03:40 PM
Boostdreamer
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Report this Post01-21-2014 11:10 AM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
86 2.8 GT with automatic.

My speedometer does this thing where sometimes it works perfectly and sometimes it starts bouncing and falling to zero. It never jumps ABOVE actual speed. Just falls then jumps back up. When this happens while using cruise control, the engine speed is affected. It revs up, etc. I have not seen the SES light come on so as far as I know, there are no codes being thrown for the VSS. The radio works fine so that should eliminate any fuse issue.

One wire to the VSS was broken and I have thought that it was the problem. I have repaired that break three times thinking that it was the problem. There is no way I'm that bad at twisting wires together. Gotta be something else. Maybe a bad wiring harness connection at the gauge? Maybe the gauge is dying?

There are plenty of speedo threads with similar problems but none with solutions.

Any thoughts?

------------------
Jonathan

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Gall757
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Report this Post01-21-2014 12:07 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thought #1 twisting wires together isn't good enough.
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Report this Post01-21-2014 01:58 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

Thought #1 twisting wires together isn't good enough.


It's a good thing that's not all I did. That was me poking fun at myself.

First time around I stripped the wires and twisted together. Then I used plenty of electrical tape to secure the break and then to support it with the alternator wire. Then replaced the wire loom.

Second time, I removed the tape, re-twisted the wires together and put a wire nut on them. Re-taped and replaced the loom.

Third time, removed the tape and wire nut, re-twisted in a different manner, covered with heat shrink tubing, separated the wires from the alternator in case it was causing interference, put on separate looms for the VSS and the alternator.

Before driving back home from school, I removed the panels under and behind the instrument cluster. I felt for looseness. On the drive home, it jumped a few times but not long enough for me to get my hands on the wires to wiggle them. I did have all of that apart at one time, months ago, to re-wire the gauge/light problem that the factory messed up.

I'll remove and re-insert the wiring harness to the speedo then drive around with the panels off for a while. It acts more like a poor connection than a component that is failing slowly.

I wanted to see it mess up again so I could watch the odometer. I cannot confirm that it does or does not work while this is happening. I THINK it also stops working. The reason I think that is because I always check my gas mileage. The mileage has been down a little and an intermittant odometer could explain that.

Jonathan

[This message has been edited by Boostdreamer (edited 01-21-2014).]

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carbon
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Report this Post01-21-2014 03:11 PM Click Here to See the Profile for carbonSend a Private Message to carbonEdit/Delete MessageReply w/QuoteDirect Link to This Post



or




Noooo...


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Boostdreamer
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Report this Post01-21-2014 05:49 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oh, I know! It is just so freaking hard to get to it! I can barely get one hand in there much less two!

Jonathan
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Report this Post01-21-2014 10:44 PM Click Here to See the Profile for grkboy707Click Here to Email grkboy707Send a Private Message to grkboy707Edit/Delete MessageReply w/QuoteDirect Link to This Post
Wire nuts are not a good fix. They should however hold the wires together well enough to temporarily fix and diagnose a problem (I've just held wires touching in my fingers to test before). I have a similar problem, and I'm hoping its just the speedo. Mine just violently pegs from 80 to 120mph. Is yours a 120 mph gauge? Hard as nails to get a hold of one though.. There is a way to test the gauge, but it requires building a complicated apparatus. If youre really good with electronics, you may want to try that route...and send it to me when youre done
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carbon
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Report this Post01-22-2014 08:25 AM Click Here to See the Profile for carbonSend a Private Message to carbonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Boostdreamer:

Oh, I know! It is just so freaking hard to get to it! I can barely get one hand in there much less two!

Jonathan


My burned fingers hear you!
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Report this Post01-22-2014 09:59 AM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, I unplugged the speedo and put it back. Drove to school this morning and the problem was not fixed. This time, the duration was long enough to see that the odometer was also NOT working while this is going on. Also the SES light finally came on and recorded a Code 24 VSS problem.

The code and the odometer not working leads me to believe that the speedo gauge itself is not at fault. I have another auto VSS so I'll swap it on and see what that does.

I agree that wire nuts are not for cars but I used what I had at the time. That wire is so small, 18 gauge I believe, that any decent connection should carry the VSS signal.

Maybe the VSS cannot produce the signal anymore? I don't really know how the VSS works or where or how the electrical signal is generated.

Jonathan
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Report this Post01-22-2014 01:11 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
I changed the VSS. It is very easy to do on an automatic. There is only the wiring harness and a bail clip to remove in order to take the VSS out.

It jumped a little bit at first then it worked perfectly after that. I drove about 10 miles or so on varied roads at varied speeds. I think this may have fixed my problem. I put my instrument cluster covers back on and replaced everything I had removed.

I'll call this the solution for now. If the problem comes back, I'll be back to report what I do and what the final fix is.

Everybody gets a plus if you don't already have one from me!

Jonathan
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Report this Post01-22-2014 01:15 PM Click Here to See the Profile for carbonSend a Private Message to carbonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am constantly amazed that my speedo works at all due the the condition the wiring to the VSS is in. The wires have obviously been pulled too hard at some point and the connector is broken. Still works though.
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Report this Post01-22-2014 02:01 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by carbon:

I am constantly amazed that my speedo works at all due the the condition the wiring to the VSS is in. The wires have obviously been pulled too hard at some point and the connector is broken. Still works though.


The connector was my dreaded worry. I was afraid that stress on the wires had caused them to pull out of the connector. THAT job would have sucked!! I guess what I would have done is to just cut the old connector off and tied into the wires of a used one. Did I mention that it is hard to work down there?!!

Jonathan

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Report this Post01-22-2014 02:23 PM Click Here to See the Profile for carbonSend a Private Message to carbonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Especially on an automatic...
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Report this Post01-22-2014 03:50 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by carbon:

Especially on an automatic...


Especially automatics with the trunk blower tubes!

Jonathan
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Report this Post01-22-2014 06:45 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
You should still ensure that wire is properly repaired. The best method is to solder and cover with a piece of heat shrink tubing. Unfortunately it's not a great location to have to get to, but any twist method will eventually fail.
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Report this Post01-22-2014 09:24 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Neils88:

You should still ensure that wire is properly repaired. The best method is to solder and cover with a piece of heat shrink tubing. Unfortunately it's not a great location to have to get to, but any twist method will eventually fail.


True. It seems like I have to take the engine out every few months so I guess I can solder this wire some time around June!

Jonathan

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Report this Post01-23-2014 07:48 AM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
The speedo quit again this morning. I guess I'll try another VSS.

Jonathan
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Report this Post01-26-2014 12:55 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
I know the plastic gear on the VSS is in good shape. I wonder about the gear that it mates to? Does anyone know if the inner gear has a history of failing?

Jonathan
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Report this Post01-27-2014 11:45 AM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Today I confirmed that engine speed is affected when the speedo cuts out. The RPM's jump up about 200 RPM's when the speedo dies. I assume this is my transaxle TCC letting go.

Does this information help anyone know what might be going on?

Jonathan
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Report this Post01-29-2014 04:40 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
I found this thread.

"Need a VSS to try out"
http://www.fiero.nl/forum/A...130314-2-113237.html

Sounds like my problem except mine is more intermittant. I'm going to try to test the VSS with the meter like in the thread. If it tests good, I have another speedo to swap in. It's been too cold to work on it lately.

Jonathan

[This message has been edited by Boostdreamer (edited 01-30-2014).]

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Report this Post02-07-2014 10:53 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
My speedometer is working again!

I started going through Bloozberry's steps, found in my link above, to identify my speedometer problem. It wasn't the gauge, it wasn't the VSS, it wasn't my broken wire repair. It was something so random I still can't believe it.

As I was checking the continuity of the wires from the VSS to the Speedometer, I found that there was a break in the purple wire. That is the one I had repaired. I moved my aligator clip to the gauge side of the break in the wire and it showed a good connection. That confirmed that there was no problem at C203 behind the arm rest.

So then I moved the aligator clip to the VSS side of the break. I had continuity there too! Wierd! I re-checked the continuity at the pin in the weather pak. Nothing.

I took it apart and removed the broken section of wire that was attached to the weather pak connector that mates with the VSS. I checked this short section of wire for continuity and there wasn't any. That was so wierd! There is absolutely no trace of visible damage to this short section of wire. The stripped strands looked good and they were tightly twisted. The connection at the end where the contact attaches was strong and solid. For some reason, this little section of wire was completely dead.

I snipped the same section of wire from my Formula parts car and put it in place. Tested the circuit and it was all good. I went for a short drive to test the speedometer and it was still stuck at zero. I was starting to get frustrated about it when I realized I hadn't plugged the connector back into the bottom of the speedo!

That was the final piece of the puzzle. I put it back and the speedo is working just fine.

Plusses for everyone who doesn't already have one from me!

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Boostdreamer
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Report this Post02-08-2014 03:40 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here is the bad piece of wire and the tool used to remove it from the weatherpack connector.

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