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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Speedometer problemsViews : 662 Replies : 10Users Viewing This Thread : |
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Feb 12th, 2021, 17:12 | #1 |
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Speedometer problems
Hi,
Is there anyone out there who repairs the speedometers on Volvo 740s/ 940s when the electronics go bad inside. Cheers, Tommy. |
Feb 12th, 2021, 18:49 | #2 |
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What's the nature of the fault?
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Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........ |
Feb 12th, 2021, 19:25 | #3 |
bob12
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You have two different oem's for the 740/60 and 940 etc. VDO and Yazaki and each has different age problem/s assuming the speedo itself is duff..
Bob |
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Feb 19th, 2021, 20:01 | #5 |
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Speedometer problems
The Yazaki unit speedo fault is often the failure of capacitors. These can be replaced if you know how or can find a good auto electrician that can solder new ones in place. Had same problem on my last 960 but in the event the capacitor had leaked and corroded the contacts on the mother board. I eventually found a replacement head but in the interim I used a cheap "heads up"display unit to keep me within the law. Good luck in your search. There is a guy down Cheltenham/ Gloucester way who might be able to help.
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Feb 21st, 2021, 21:04 | #6 |
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I'm getting an intermittent reading on the speedo. On moving off the speedo jumps up to 40mph mark and then back to zero.? When the speedo is reading okay, so is the odometer. When speedo fails, odometer stops. Checked the connection at the rear axle sensor, looks fine, no loose wires or corrosion. Same with the instrument cluster. Ran a separate earth from the diff. sensor, just in case, still no joy. Does the actual diff. sensor go bad on these cars.? Milage is 68000 miles with the VDO instrument cluster. Took out the back seat but can't find any connectors in there.
Cheers, Tommy. |
Feb 21st, 2021, 21:19 | #7 | |
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Quote:
You won't find any connections under the back seat regardless of whether it's a saloon or estate but the wiring is in slightly different places for each.
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Feb 22nd, 2021, 20:51 | #8 |
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Mine does the same thing, but I've got a Yazaki speedo. Usually correlates with heavy rain, or leaving the car sitting for more than a day or two. I assume there is some moisture build up behind the dash which is causing it, as it seems to sort itself out if i run the heater fan on full heat and forward for an hour or so.
I have a replacement cluster for when the time comes but try to get the heater running on the dash vents so it gets the dash warm and see if that helps for a temporary fix. |
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Feb 23rd, 2021, 11:22 | #9 |
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I had a problem with the back axle wire touching the metal work for spare wheel well behind it. It wore a hole in the wire making an intermittent short.
If there is no speed signal the fuel ECU will engage a limp mode with a high idle if you use full power. There is a spare terminal on the speedo for the speed signal, if you had a scope or pulse detector, or maybe just AC voltage measurement you could check it and determine if its the speed signal or the speedo. |
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Mar 3rd, 2021, 14:43 | #10 |
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Hi Dave, It's a 1986 GL Volvo 740 saloon. It doesn't have ABS fitted.
Cheers, Tommy. |
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