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post #1 of 10 (permalink) Old 04-30-2019, 08:56 PM Thread Starter
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Speedo Sensor

Hi Everyone,

I've been repeated trying to working on fixing the spedsor sensor in my my 1983 Alfetga GTV 2.0
I have tried replaceding the wiring, speedo gear, speedo seansor, etc but nothing seems to work.
I have heard in the the gtv6 modles there is a speedi sensso under the passanger seat but that is not the case for this car.
Any help would be appricated.

Regards,

Rob.











a

Rob
83 Alfetta GTV 2L
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post #2 of 10 (permalink) Old 06-02-2019, 10:29 AM
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cpsgtv6

Hey Rob - did you have any luck on this problem? Yeah, I'm pretty sure the sensor/sender feeds directly to the instrument cluster on your car as you mentioned, the Milanos have additional circuitry upstream of the sensor to make convert the signal. Actually, it's the same circuitry, just a smarter place for the sensitive electronics!

If you haven't already, I would:
-Verify sensor is getting voltage by checking leads at the sensor.
-Bench test sensor to verify functional.

If those check out, try continuity checks between the sensor wire and instrument cluster. If that works, then the issue might be related to your speedometer display/display. Related question: does your odometer work? It works off the same signal from the speedo sensor, so if your odo works but needle doesn't, it's probably your speedometer/display.
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post #3 of 10 (permalink) Old 06-02-2019, 11:04 AM
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Quote:
Actually, it's the same circuitry, just a smarter place for the sensitive electronics!
that was only on 85.5 and 86 GTV6's.
AFAIK, Alfettas and pre 85.5 GTV6's share the same sensor. There was one posted in the parts for sale forum a day or two ago. The Alfetta/early GTV6 sensor is smaller than the late GTV6 and Milano senors and they cannot be interchanged.

Ed Prytherch
79 Spider
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #4 of 10 (permalink) Old 06-02-2019, 04:43 PM
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that was only on 85.5 and 86 GTV6's.
Hmm - the wiring diagram for my '86 GTV6 doesn't show an upstream circuit board - just feeds directly into the instrument cluster. I'm in the process of repairing my sensor, it has all of the electronics in it (specifically the SAF 1091 chip which I believe is the cause of failure. If anyone knows a good/cheap source for these guys please let me know!).

Yep, there are (at least) two sensor models for the GTV6 and they cannot be interchanged.
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post #5 of 10 (permalink) Old 06-02-2019, 05:15 PM
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AFAIK the senders for 86 GTV6's have been NLA for a long time. They were notoriously unreliable. You can use a Milano sender + amplifier box.

I have repaired several boxes with the SAF 1091 chip and I have a couple of new chips but the problem was always the output transistor. If the output wire is shorted to ground with the power on then it blows the transistor.

There is a lot of information here: https://www.alfabb.com/bb/forums/mil...amplifier.html
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Ed Prytherch
79 Spider
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #6 of 10 (permalink) Old 06-02-2019, 05:42 PM
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Wow, that post is super informative. Thanks for the link.

I did a rudimentary "diode" check on the transistor using a multimeter, it seemed passed that, but not sure how effective that check is. It's a BC 308C PNP transistor. Since transistors are cheap, do you think that would be worth replacing before swapping the chip? Here's a pic of the board:

Edit I removed my transistor and repeated your IC pin-out (pin-6) voltage check which feeds into the transistor. Chip is outputting rock-steady +11.5V (should be 0), so I think this means the chip is toasted. Thanks again for the detailed tech work, that made troubleshooting a lot easier.
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Last edited by cpsgtv6; 06-02-2019 at 06:23 PM.
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post #7 of 10 (permalink) Old 06-02-2019, 07:53 PM
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let me know if you need a chip. I can part with one of mine.

My first check is to hook up the sender, apply 12V and put a scope on a sender wire and verify that I have the high frequency sine wave.

Ed Prytherch
79 Spider
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #8 of 10 (permalink) Old 06-02-2019, 08:47 PM
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Unfortunately I don't have an oscilloscope on hand - I think I'll bring it in to work tomorrow to test it out. Would definitely be interested in in the chip if you are OK with selling it... thanks!
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post #9 of 10 (permalink) Old 06-02-2019, 09:53 PM
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Remind me in 5 days when I will be home from vacation

Ed Prytherch
79 Spider
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #10 of 10 (permalink) Old 06-08-2019, 12:54 AM
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Hey alfaparticle - welcome back! I'm still interested in the chip if you're still willing to part with one. I ran a scope on my chip and it does seem to be dead. No high frequency sine wave, just garbled noise.
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