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Speedometer not working.... All other gauges fine. by 86Red2M6
Started on: 08-05-2012 12:02 AM
Replies: 15 (4197 views)
Last post by: Boxdin on 07-28-2013 07:30 AM
86Red2M6
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Report this Post08-05-2012 12:02 AM Click Here to See the Profile for 86Red2M6Click Here to Email 86Red2M6Send a Private Message to 86Red2M6Edit/Delete MessageReply w/QuoteDirect Link to This Post
Okay, I've searched the threads, and I've found a lot of info to point me in the right direction. However, my situation may be unusual, and wanted some input since this is my son's first car and he has a VERY limited budget.
When we bought this car, it didn't run, so I couldn't test anything. We have worked out a lot of problems, car runs great now, but the Speedo still does nothing. I have checked the radio fuse and connections at sensor, cluster and fuse box, which pretty much narrows it down to bad speedo or sensor. However, one interesting fact is that the previous owner told me when the car quit, there was "a box smoking, and wires burning"... He pointed over by the servo for the cruise control to a small box mounted next to it, with wires running from the servo. I simply disconnected it, figuring cruise can wait until everything else is fixed. I do know that the cruise feeds off the same signal as the speedo, and wondered if the speed sensor was sending too high of voltage to the cruise and that's why it was smoking, which could have also burnt up the coils in the speedometer. (This would mean both are bad)... Or perhaps the cruise shorted and burnt the wiring and damaged the harness from the speed sensor meaning no signal to the speedometer.... I checked the continuity and it seems good. But I know when testing wiring in these cars you need to disconnect everything so you aren't getting a false reading. So before I tear everything apart looking for this gremlin, I wondered if anyone had any advice / tricks up their sleeves or known common issues I could check for first.
Also, which is more common, bad sensor or bad speedometer? Oh, in case it matters, 86 V6 SE Automatic. Notchback.
Thanks in advance.
-Ty

[This message has been edited by 86Red2M6 (edited 08-05-2012).]

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tucsonsean
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Report this Post08-05-2012 12:25 AM Click Here to See the Profile for tucsonseanClick Here to Email tucsonseanSend a Private Message to tucsonseanEdit/Delete MessageReply w/QuoteDirect Link to This Post
I offer you no advice and no hope, Ty, but I wanted to bump your thread because I'm still fighting with mine. Good grounds,12v to connector, continuity both wires VSS to cluster, new VSS, new VSS gear--I even tried replacing the entire cluster. All gauges working, but still no speedo, odometer or trip odometer, still throwing a code, check engine light on, ergo, no emissions possible and no registration. Been working on the problem over a month. So it sits in the driveway and occasionally gets driven around the block. I feel your pain. And I'm [i]this[i] close to becoming an ex-Fiero owner.

------------------
tucsonsean
'85 2m4 Sport Coupe, "Ol' Yeller"

[This message has been edited by tucsonsean (edited 08-05-2012).]

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CowsPatoot
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Report this Post08-05-2012 01:49 AM Click Here to See the Profile for CowsPatootClick Here to visit CowsPatoot's HomePageSend a Private Message to CowsPatootEdit/Delete MessageReply w/QuoteDirect Link to This Post
Verify the ground at pin M of the C203.
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tucsonsean
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Report this Post08-05-2012 05:01 PM Click Here to See the Profile for tucsonseanClick Here to Email tucsonseanSend a Private Message to tucsonseanEdit/Delete MessageReply w/QuoteDirect Link to This Post
If the ground is bad at C203, wouldn't that affect all the gauges running through there?
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IFLYR22
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Report this Post08-05-2012 06:31 PM Click Here to See the Profile for IFLYR22Click Here to Email IFLYR22Send a Private Message to IFLYR22Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by tucsonsean:

If the ground is bad at C203, wouldn't that affect all the gauges running through there?


Not necessarily, as that would be the VSSB ground, which should be engine grounded.

86Red2M6:
The speedometer gets the full signal (4,000 PPM, Pulse Per Mile) from the VSS on a Yellow (VSS high) and Purple w/ White stripe (VSS low) wire set. The speedometer circuit board is a buffer/filter that then send a conditioned signal (2,000 PPM) to the ECM and the Cruise Control module.
The VSS is a magnetic pick up, in with (sticking out the top of) your Governor (the Governor controls up shift point).
Have you verified continuity of the Purple w/ White stripe and Yellow wires from the VSS to the Speedometer (pins R & S, not pin T which is a Yellow with Black Stripe wire that is power)?
Check Pin T for +12V and Pin P for ground at the speedometer.
Pin U (Green w/ White Stripe) & N (Brown) are your Cruise and ECM outputs.

Speedometers seem to go bad before the VSS's do, but the most common issue is wires.

-Dave

Adding:
If the VSS circuit is bad (as in VSS, Speedometer Board, Wires, etc don't work), the ECM should be setting a code 24 with the Service Engine Soon light turning on.

[This message has been edited by IFLYR22 (edited 10-08-2012).]

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86Red2M6
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Report this Post08-06-2012 12:00 AM Click Here to See the Profile for 86Red2M6Click Here to Email 86Red2M6Send a Private Message to 86Red2M6Edit/Delete MessageReply w/QuoteDirect Link to This Post
No check engine codes. reads 12 12 12 pause 12 12 12. So I will get out the multimeter and start checking the other things you suggested. Thanks for the starting point.
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IFLYR22
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Report this Post08-06-2012 09:54 AM Click Here to See the Profile for IFLYR22Click Here to Email IFLYR22Send a Private Message to IFLYR22Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 86Red2M6:

No check engine codes. reads 12 12 12 pause 12 12 12. So I will get out the multimeter and start checking the other things you suggested. Thanks for the starting point.


Well, that would suggest that the VSS circuit is working.
If the above wires are correct, and the ECM is getting a 2,000 PPM signal, the speedometer board is working. That would suggest the air core movement (part on the board that moves the needle) has failed.

-Dave
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fierohoho
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Report this Post08-06-2012 12:24 PM Click Here to See the Profile for fierohohoClick Here to Email fierohohoSend a Private Message to fierohohoEdit/Delete MessageReply w/QuoteDirect Link to This Post
A couple thoughts:

The 10 amp fuse for the radio also runs the speedo and cruise control, if the fuse is not blowing then there should be no short to keep the speedo from working.

When the car is started does the needle zero out on the speedometer?

When you say the speedo doesn't work does that mean it does not move when the car is being driven?

If it does not work while the car is being driven I would first check to see if the gear is still on the end of the speed sensor in the transmission.

If you're not careful when you pull the sensor the gear can come loose and fall inside the pan, no gear, no sensor input for the speedo.
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86Red2M6
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Report this Post08-06-2012 02:53 PM Click Here to See the Profile for 86Red2M6Click Here to Email 86Red2M6Send a Private Message to 86Red2M6Edit/Delete MessageReply w/QuoteDirect Link to This Post
The speedo sits on zero with no power and doesn't move when turned on or driven. This car only had reverse when we bought it. It had a bad alternator that led to many electrical problems, so I wasn't paying attention to any of the gauges in the beginning. After fixing the alternator, all dummy lights went out and all gauges started working correctly except the speedometer. As far as the trans issue, that turned out to be the sleeve on the shifter rod inside the trans. The sleeve that engages the park pawl lock was getting caught and the shifter couldn't be moved past reverse. It is possible the speedo gear was in the pan, because the seller actually lied to me about not knowing why it wouldn't shift past reverse. They claimed they hadn't taken anything apart, but a suspicious zip lock bag in the trunk contained the pieces of sleeve from the internal rod. So someone had the trans pan off. Whether or not there was a gear in there I'll never know. I guess I will pull the vss out this weekend and look for a gear if the other electrical solutions don't point me elsewhere.

And a always, thanks.
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tucsonsean
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Report this Post08-06-2012 07:48 PM Click Here to See the Profile for tucsonseanClick Here to Email tucsonseanSend a Private Message to tucsonseanEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm hijacking 86red's thread (again) 'cause I'm having a similar problem--all the gauges work except the speedometer.

Things I've checked so far:

--continuity ok from VSS to connector at cluster for both purple and yellow wires
--radio fuse intact, and 12v to the power wire at connector
--good ground at cluster connector
--new VSS and new gear still on end of sensor
--new Weatherlock connector at VSS
--even replaced the entire cluster

Fierohoho: my speedo sits at 20mph when ignition off, and stays there when driving.

IFLYR22: Living in Tucson, I know you understand my angst. My ECM is throwing a code 24 every time and lighting up the "check engine" light. If the light's on, no emissions test; no emissions test here in Pima County = no registration. BTW, I haven't checked the ground at C203 yet.

------------------
tucsonsean
'85 2m4 Sport Coupe, "Ol' Yeller"

[This message has been edited by tucsonsean (edited 08-06-2012).]

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IFLYR22
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Report this Post08-07-2012 01:26 AM Click Here to See the Profile for IFLYR22Click Here to Email IFLYR22Send a Private Message to IFLYR22Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 86Red2M6:

The speedo sits on zero with no power and doesn't move when turned on or driven. This car only had reverse when we bought it. It had a bad alternator that led to many electrical problems, so I wasn't paying attention to any of the gauges in the beginning. After fixing the alternator, all dummy lights went out and all gauges started working correctly except the speedometer. As far as the trans issue, that turned out to be the sleeve on the shifter rod inside the trans. The sleeve that engages the park pawl lock was getting caught and the shifter couldn't be moved past reverse. It is possible the speedo gear was in the pan, because the seller actually lied to me about not knowing why it wouldn't shift past reverse. They claimed they hadn't taken anything apart, but a suspicious zip lock bag in the trunk contained the pieces of sleeve from the internal rod. So someone had the trans pan off. Whether or not there was a gear in there I'll never know. I guess I will pull the vss out this weekend and look for a gear if the other electrical solutions don't point me elsewhere.

And a always, thanks.


I still sit at the speedometer circuit board not sending a signal to the air core movement of the speedometer needle, since you are not getting a code 24 from the ECM.
The ECM should through a code 24 if the VSS gear was not there, or the Speedometer circuit board was not working...
Do your odometers work? Do you see the mileage count up as it is driven?

-Dave
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IFLYR22
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Report this Post08-07-2012 01:35 AM Click Here to See the Profile for IFLYR22Click Here to Email IFLYR22Send a Private Message to IFLYR22Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by tucsonsean:

...snip...



PM Sent.

-Dave
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86Red2M6
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Report this Post08-07-2012 03:55 AM Click Here to See the Profile for 86Red2M6Click Here to Email 86Red2M6Send a Private Message to 86Red2M6Edit/Delete MessageReply w/QuoteDirect Link to This Post
tucsonsean... You're welcome to hijack it... Maybe we'll help eachother figure this out. And checking the odometer is something I hadn't even thought of. (I like that I don't have to take anything apart to do that!) Thanks, Dave.
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Report this Post08-07-2012 04:37 PM Click Here to See the Profile for avlonfrgClick Here to Email avlonfrgSend a Private Message to avlonfrgEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had the same speedometer problem a few months ago on a 87 GT. Took the unit out of the gauge cluster and bought a replacement off eBay. It now works fine. You can easily change the odometer reading to match the actual on the replaced unit, by searching the 'net and finding instructions. Fairly simple but requires a steady hand.

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John W
Baltimore

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86Red2M6
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Report this Post07-27-2013 03:08 PM Click Here to See the Profile for 86Red2M6Click Here to Email 86Red2M6Send a Private Message to 86Red2M6Edit/Delete MessageReply w/QuoteDirect Link to This Post
I realize it's been forever since I worked on this. Suspension problems made electrical secondary. The ground wire in the engine compartment must have broken at some point, although the engine was never pulled, so I'm not sure how it happened. soldering the ground seems to have corrected all problems. You guys were right, wiring was the culprit.
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Boxdin
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Report this Post07-28-2013 07:30 AM Click Here to See the Profile for BoxdinClick Here to Email BoxdinSend a Private Message to BoxdinEdit/Delete MessageReply w/QuoteDirect Link to This Post
I just replaced my speedo coz it quit working. While in there I noticed the printed board was delaminated in a couple of corners and the plug ins had considerable corrosion on the lugs. Both of those could have been the problem, might not have been speedo, but all went back together great and now works like a charm. Check those other items too besides speedo.
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