Speedo Fix failed - What to try next?

From CEM to VEM, from LED to lightbulb and more. If you have an electrical problem, like a broken info-centre, search for answers in this category. This is also the place to be when you expect the problem to be of an electrical nature...

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MisterH
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Speedo Fix failed - What to try next?

Post by MisterH » Mon Jul 15, 2019 12:06 pm

Good Day everyone

As you may know, I have been having speedo trouble with the speedometer not showing any speed and as such the Odometer is not turning over.
I have tried Jaster's solution of re-soldering dry joints, of which there were some, however after reinstalling, nothing has changed.

Here are the circumstances, unchanged since we got the car:
Rev counter WORKS
Info Centre WORKS (except settings related to avg speed, fuel Avg or fuel Inst)
The Speedometer and Odometer DO NOT WORK.

So far, as well as re-soldering the dry joints, the sensor itself has been resistance tested, which was fine, So I am at a loss as to what to do next, having followed all the advice I could find.

brinkie advised me to set up a forum post, so if we find a fix, future generations of 480 owners will be able to find it here.

if the info centre is not getting a reading, does that mean the sensor IS faulty after all?

this is the major issue my car faces, and I would like to get it sorted as soon as possible, as the car is used fairly regularly and I would like the mileage to be not too far from the odometer reading.

My car is a 1988 480ES B18E, with the Red and Yellow dashboard connectors, should that help.

Many thanks
Ben H
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Fix Speedometer
New Tires
Fix Radio/Cassette
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Re: Speedo Fix failed - What to try next?

Post by brinkie » Mon Jul 15, 2019 12:47 pm

If the sensor measures around 3 ohms (give or take a few ohms), the sensor is correct. (Usually)
On the main board with the yellow and red connectors, there is a four-pin receptable which accepts four large pins from the speedometer/odometer assembly. They protrude through the main board. With a pair of small pliers, squeeze the receptacles a bit so the pins fit tight.
If that doesn't work, I will look up the pins in the red and yellow connectors that are connected to the speedometer sensor, so you can measure from there if there is a good connection to the speed sensor.
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Mon Jul 15, 2019 3:29 pm

brinkie wrote:
Mon Jul 15, 2019 12:47 pm
If the sensor measures around 3 ohms (give or take a few ohms), the sensor is correct. (Usually)
On the main board with the yellow and red connectors, there is a four-pin receptable which accepts four large pins from the speedometer/odometer assembly. They protrude through the main board. With a pair of small pliers, squeeze the receptacles a bit so the pins fit tight.
If that doesn't work, I will look up the pins in the red and yellow connectors that are connected to the speedometer sensor, so you can measure from there if there is a good connection to the speed sensor.
If that is the thing I think it is (the four large pins that is) Those had been soldered when I had a look at it, and I had to resolder them myself, but the connection seemed a bit strained, so that may be the source of the issue
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Fix Speedometer
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Re: Speedo Fix failed - What to try next?

Post by arthuy » Mon Jul 15, 2019 3:40 pm

Read this and see how you get on, the coaxial cable is awful. You need to prove continuity between both ends, if you have a multi meter great if not you need one.
arthuy wrote:
Mon Jul 10, 2017 11:57 pm
Getting a tad frustrated with the speedo.

I cant see anything particularly wrong with the sensor (it measures a couple of ohms) the wiring all looks ok and the dash was refurbed.

I would like to test the speed sensor by substitution but cant seem to find one anywhere so I am quite stuck and out of ideas. any help would be great.

I am going to recheck the readings at the dash plugs.

Image

From the diagram there is a wire from the ECU to the speedo (Green pin 9), does any one know what the expected conditions should be? is it a voltage, resistance or a ground.

On the grey plug I expect to see the same resistance as at the plug below the air filter.

arthuy wrote:
Tue Jul 11, 2017 12:52 pm
Panic over it is wiring which is faulty.

I followed my own old advice, 'go to bed and look at it in the morning'.

Armed with the diagram I found the 2 wires, they are quite obvious in the loom being green and black in a separate sleeve from the other wires going to the GRAY plug. PIN 6 and 12 are next to each other.

I first bridged the plug in the engine bay and probed at the plug but no continuity. Next up I wanted a length of wire to attach at the plug and test the wires individually.

Image

I am at times amazed with the parts I pick up, I put my hands on this twin cable I bought for wiring in a highlevel brake light a year or so back which just so happened to have the same connector as the VSS so plugged straight on to the loom and had more than enough cable to reach the dash board.

Image
arthuy wrote:
Tue Jul 11, 2017 1:02 pm
A very quick probe with my meter proved that the Black wire was broken. I double checked by bridging the grey plug pins and test at the engine bay. Same results but I looked closer at the cable and the black did look some what flat or stretched. Stripping off the plastic it was pretty obvious.

Image

Just to be 100% sure I strapped the broken wire up and hey presto I have a speedo again.

Image

Looking at how the wire has failed explained the symptoms from the previous owner, it was working intermittently, probably a few strands kept the signal going until it finally gave up.

Seeing as I have a suitable piece of wire I will run fit that and eliminate the original. It is tempting to cut it back and hook it up but that would just leave an unknown.

Unfortunately I dont have a spare plug for it though I am sure I have a packet hiding in the garage somewhere, but they are easy to obtain and hopefully the ones I have ordered will turn up later in the week.

Moral of the story is check the basics properly.

Need to crack on with getting the brakes back on although I am still waiting for the brake tubing to turn up.
The quick way is use a paper clip or stiff wire to loop the cable, I did it at the speedo head side then check from the other side there is continuity.

The connector plugs are cheap from ebay and make good test leads as per the post.

Although it looks like there as two wires (green and black) it is a coaxial type cable which you can just make out from my photos. The Black cable becomes a braid wrapped around the insulation of the green. The braided wire on mine had broken in several places so I replaced with the two core cable as per my photo.

Image

https://www.ebay.co.uk/itm/2ps-Auto-Car ... :rk:1:pf:1 2 pin connectors.

Once you get your head around it is easy to see why it breaks.

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Re: Speedo Fix failed - What to try next?

Post by Murf » Mon Jul 15, 2019 8:45 pm

I had the same issue with my 94 GT and it was the speedo cable plug under the airbox that was at fault.
The wiring was snapped as in the post above. I cut the plug off both ends and soldered the ends together.

Works perfectly 👍😁
Megane 225 Cup
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Re: Speedo Fix failed - What to try next?

Post by MisterH » Tue Jul 16, 2019 1:19 pm

arthuy wrote:
Mon Jul 15, 2019 3:40 pm
Read this and see how you get on, the coaxial cable is awful. You need to prove continuity between both ends, if you have a multi meter great if not you need one.
arthuy wrote:
Mon Jul 10, 2017 11:57 pm
Getting a tad frustrated with the speedo.

I cant see anything particularly wrong with the sensor (it measures a couple of ohms) the wiring all looks ok and the dash was refurbed.

I would like to test the speed sensor by substitution but cant seem to find one anywhere so I am quite stuck and out of ideas. any help would be great.

I am going to recheck the readings at the dash plugs.

Image

From the diagram there is a wire from the ECU to the speedo (Green pin 9), does any one know what the expected conditions should be? is it a voltage, resistance or a ground.

On the grey plug I expect to see the same resistance as at the plug below the air filter.

arthuy wrote:
Tue Jul 11, 2017 12:52 pm
Panic over it is wiring which is faulty.

I followed my own old advice, 'go to bed and look at it in the morning'.

Armed with the diagram I found the 2 wires, they are quite obvious in the loom being green and black in a separate sleeve from the other wires going to the GRAY plug. PIN 6 and 12 are next to each other.

I first bridged the plug in the engine bay and probed at the plug but no continuity. Next up I wanted a length of wire to attach at the plug and test the wires individually.

Image

I am at times amazed with the parts I pick up, I put my hands on this twin cable I bought for wiring in a highlevel brake light a year or so back which just so happened to have the same connector as the VSS so plugged straight on to the loom and had more than enough cable to reach the dash board.

Image
arthuy wrote:
Tue Jul 11, 2017 1:02 pm
A very quick probe with my meter proved that the Black wire was broken. I double checked by bridging the grey plug pins and test at the engine bay. Same results but I looked closer at the cable and the black did look some what flat or stretched. Stripping off the plastic it was pretty obvious.

Image

Just to be 100% sure I strapped the broken wire up and hey presto I have a speedo again.

Image

Looking at how the wire has failed explained the symptoms from the previous owner, it was working intermittently, probably a few strands kept the signal going until it finally gave up.

Seeing as I have a suitable piece of wire I will run fit that and eliminate the original. It is tempting to cut it back and hook it up but that would just leave an unknown.

Unfortunately I dont have a spare plug for it though I am sure I have a packet hiding in the garage somewhere, but they are easy to obtain and hopefully the ones I have ordered will turn up later in the week.

Moral of the story is check the basics properly.

Need to crack on with getting the brakes back on although I am still waiting for the brake tubing to turn up.
The quick way is use a paper clip or stiff wire to loop the cable, I did it at the speedo head side then check from the other side there is continuity.

The connector plugs are cheap from ebay and make good test leads as per the post.

Although it looks like there as two wires (green and black) it is a coaxial type cable which you can just make out from my photos. The Black cable becomes a braid wrapped around the insulation of the green. The braided wire on mine had broken in several places so I replaced with the two core cable as per my photo.

Image

https://www.ebay.co.uk/itm/2ps-Auto-Car ... :rk:1:pf:1 2 pin connectors.

Once you get your head around it is easy to see why it breaks.
Thank you, I might try that, however scary it looks! is this possible while on a driveway, or do I need some more specialist surroundings?
Current Jobs to do (17/08/19):
Fix Speedometer
New Tires
Fix Radio/Cassette
Fix Central Locking

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Tue Jul 16, 2019 1:26 pm

Murf wrote:
Mon Jul 15, 2019 8:45 pm
I had the same issue with my 94 GT and it was the speedo cable plug under the airbox that was at fault.
The wiring was snapped as in the post above. I cut the plug off both ends and soldered the ends together.

Works perfectly 👍😁
I assume this is not the sensor itself? as I think we have soldered A Plug already, while trying to fix it, I am not sure if this is the right plug though, either way, It can't harm the car if I got the wrong plug I am sure
Current Jobs to do (17/08/19):
Fix Speedometer
New Tires
Fix Radio/Cassette
Fix Central Locking

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Re: Speedo Fix failed - What to try next?

Post by arthuy » Tue Jul 16, 2019 5:16 pm

Hardest part is pulling the dash out, very easy to do.

Try bridging the pins at the dash plug, very obvious which ones they are as sort of separate from the other wires. (green and black are speedo).

The cable from the connector in the engine bay can break in multiple places, which is why it is best to check continuity between both ends rather than just fixing the breaks that are easy to spot.

Have been in the same position as you so know get there in the end.

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Tue Jul 16, 2019 5:41 pm

arthuy wrote:
Tue Jul 16, 2019 5:16 pm
Hardest part is pulling the dash out, very easy to do.

Try bridging the pins at the dash plug, very obvious which ones they are as sort of separate from the other wires. (green and black are speedo).

The cable from the connector in the engine bay can break in multiple places, which is why it is best to check continuity between both ends rather than just fixing the breaks that are easy to spot.

Have been in the same position as you so know get there in the end.
Okay, I have already pulled the dash out once, as there was only 1 screw holding it in, it is quite straightforward, the dash plug is the red and yellow connectors I assume ('88 MY)?
Current Jobs to do (17/08/19):
Fix Speedometer
New Tires
Fix Radio/Cassette
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Re: Speedo Fix failed - What to try next?

Post by brinkie » Thu Jul 18, 2019 9:41 am

Hold on, the speedo cable in the early models is not using shielded cable. I will try and look the exact specifications tonight, I have a specimen of the red and yellow connectors and a piece of the wiring harness. However, I am a bit forgetful lately, having worked until 1 am last night while the alarm clock rings at 7 am. So if I haven't responded, feel free to remind me. :)
(Driving home on twisty and completely quiet back roads at 1 o'clock in the morning, in the 480 with its main and auxiliary beams on, is a joy that makes up for all the trouble, though!)
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Sat Jul 20, 2019 11:32 am

brinkie wrote:
Thu Jul 18, 2019 9:41 am
Hold on, the speedo cable in the early models is not using shielded cable. I will try and look the exact specifications tonight, I have a specimen of the red and yellow connectors and a piece of the wiring harness. However, I am a bit forgetful lately, having worked until 1 am last night while the alarm clock rings at 7 am. So if I haven't responded, feel free to remind me. :)
(Driving home on twisty and completely quiet back roads at 1 o'clock in the morning, in the 480 with its main and auxiliary beams on, is a joy that makes up for all the trouble, though!)
did you get a chance to read it then? and if so what is the verdict?
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Re: Speedo Fix failed - What to try next?

Post by Van » Sat Jul 20, 2019 6:13 pm

I just want to express my compassion. In my 480 time I had struggled with this long time and it nearly drove me mad. Changed dashes and computers several times, in the end the cause seems to have been the speed sensor.

Temporarily workarounds:
-take notes of rpm vs speed
-speed tickets usually are a good indicator of the real speed
-use sat nav with speed indicated
-use smart phone with sat nav with speed indicated
-use smart phone with any speedo meter app
-buy a car that's not a Volvo 480 :rofl:

Good luck.
after over 10 years parted with the 1995 Volvo 480 ES 2.0

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Re: Speedo Fix failed - What to try next?

Post by Alan 480 » Sat Jul 20, 2019 6:55 pm

Van wrote:
Sat Jul 20, 2019 6:13 pm

Temporarily workarounds:
-take notes of rpm vs speed

Good luck.
best to note 4th & 5th approx revs to speed.

I use
2 x rpm = mph in 4th
2.5 x rpm = mph in 5th

two litre version K10753 seems to ring a bell as the constant, 12 pulses per revolution of drive shaft and then various calcs means 10753 pulses per mile :-)
Alan

480 ES 2litre x 2, C30 1.8ES, SS1

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Re: Speedo Fix failed - What to try next?

Post by brinkie » Mon Jul 22, 2019 6:43 pm

Van wrote:
Sat Jul 20, 2019 6:13 pm
I just want to express my compassion. In my 480 time I had struggled with this long time and it nearly drove me mad. Changed dashes and computers several times, in the end the cause seems to have been the speed sensor.
[...]
after over 10 years parted with the 1995 Volvo 480 ES 2.0
and haven't stopped gloating ever since?
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

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Re: Speedo Fix failed - What to try next?

Post by brinkie » Mon Jul 22, 2019 7:12 pm

MisterH wrote:
Sat Jul 20, 2019 11:32 am
did you get a chance to read it then? and if so what is the verdict?
Again, swamped in trivial and non-trivial stuff... but I have grabbed the green book and found the information you required :)

The signal is split over two connectors:
Red connector pin 3 (black-brown wire) is the speedometer signal
Yellow connector pin 6 (yellow-brown wire) is the signal ground

If you have a smartphone and an audio cable with 3.5mm jack, you can create a test signal. The smartphone needs to run an app like "Simple tone generator", plug in the cable in the audio jack of the phone and connect the wires of the audio cable to the speedometer sensor connector under the air filter box. A 400 Hz signal should give a speed reading of approximately 160 mph.
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Tue Jul 23, 2019 10:01 am

brinkie wrote:
Mon Jul 22, 2019 7:12 pm
MisterH wrote:
Sat Jul 20, 2019 11:32 am
did you get a chance to read it then? and if so what is the verdict?
Again, swamped in trivial and non-trivial stuff... but I have grabbed the green book and found the information you required :)

The signal is split over two connectors:
Red connector pin 3 (black-brown wire) is the speedometer signal
Yellow connector pin 6 (yellow-brown wire) is the signal ground

If you have a smartphone and an audio cable with 3.5mm jack, you can create a test signal. The smartphone needs to run an app like "Simple tone generator", plug in the cable in the audio jack of the phone and connect the wires of the audio cable to the speedometer sensor connector under the air filter box. A 400 Hz signal should give a speed reading of approximately 160 mph.
Thanks Brinkie, I assume these red and yellow connectors are the ones that are behind the dash?
Current Jobs to do (17/08/19):
Fix Speedometer
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Re: Speedo Fix failed - What to try next?

Post by brinkie » Tue Jul 23, 2019 11:56 am

That assumption is correct. :)
There are tiny numbers inside the connectors on the instrument cluster which correspond to the pin numbers.
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Wed Jul 24, 2019 10:40 am

brinkie wrote:
Tue Jul 23, 2019 11:56 am
That assumption is correct. :)
There are tiny numbers inside the connectors on the instrument cluster which correspond to the pin numbers.
How would I make the audio wires connect to the speedo sensor connector?
Current Jobs to do (17/08/19):
Fix Speedometer
New Tires
Fix Radio/Cassette
Fix Central Locking

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Re: Speedo Fix failed - What to try next?

Post by arthuy » Wed Jul 24, 2019 12:10 pm

If you bare the ends and run a but of solder over the wire it gives you a stiff pin to insert.

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Re: Speedo Fix failed - What to try next?

Post by MisterH » Wed Jul 24, 2019 2:11 pm

arthuy wrote:
Wed Jul 24, 2019 12:10 pm
If you bare the ends and run a but of solder over the wire it gives you a stiff pin to insert.
Ok, shall try that, thanks!
Current Jobs to do (17/08/19):
Fix Speedometer
New Tires
Fix Radio/Cassette
Fix Central Locking

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