Oil on speed sensor

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suddy
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Oil on speed sensor

Post by suddy » Tue Aug 29, 2017 9:19 am

I have been having intermittent problems with my speed sensor (not the dashboard, rather the feed to the ECU).

So, I took it out the other day to clean it, to find some gear oil on the sensor. Could this be the cause of the problems I'm getting? The sensor is a sealed unit, so I couldn't imagine oil being a problem, plus there is an o-ring on the sensor (is that to retain any oil?), but, do I have a bigger problem here, maybe an internal gearbox leak?

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Stephen
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Re: Oil on speed sensor

Post by brinkie » Tue Aug 29, 2017 10:30 am

I would start worrying if there were NO traces of oil on the sensor, because it functions by measuring the proximity of gear teeth inside the geabox, which should be filled with gearbox oil! The sensor is nothing more than a coil, both ends of the coil are connected to the speedometer, which forms an oscillator circuit through this coil. If a gearbox tooth passes the sensor, the oscillator will be temporarily stopped, which causes a pulse train representing the vehicle speed.

It should not leak oil through the sensor, though.
Robert.

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Re: Oil on speed sensor

Post by brinkie » Tue Aug 29, 2017 11:20 am

suddy wrote:I have been having intermittent problems with my speed sensor (not the dashboard, rather the feed to the ECU).
What do you mean by feed to the ECU? There is an output to the ECU (which is also used for cruise control) but the speedometer-ECU connection is almost never at fault (I have never seen it fail, but never say never with a 480 and electrics :lol:)

Intermittent problems can have three causes.
1. Wiring to the sensor is faulty. Usually the connector that links the sensor wiring loom (shielded cable with 2 leads inside) with the main engine loom. You can find the connector underneath the air filter box. Solution: cut off the connectors and solder the wires together. In some cases however, the sensor itself has broken wiring; check with an ohmmeter across the terminals of the connector, it should be around 3 ohms (or slightly more, depending on the quality of the multimeter)
2. Soldering on the instrument cluster main board is faulty. Solution: solder the pins of the 2 big connectors (from 1989 onwards they are coloured grey and green) again.
3. The electronics on the speedometer itself are faulty. Solution: don't have one currently, I usually replace the board. But this is rarely an intermittent problem, if the electronics fail, it stops working.

If the speedometer is not working but the odometer and trip counter are working, your speed sensor is fine, the meter is broken. (Reset the average speed on the info centre and if it shows speed, the sensor is good)
If the odometer and trip counter are not working but the speedometer is, the odometer gear is broken (common fault).
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: Oil on speed sensor

Post by suddy » Wed Aug 30, 2017 9:31 am

I would expect its option 1. The avg speed was no longer being reported, the feed to the car radio was not working, and after driving at speed to a stop at a junction the engine would stall, which leads me to believe its the feed to the ECU rather anything from the ECU.

Just for some background; The problem started after I drove through some quite deep standing water - I disconnected the connector and re-connected, because there was water in the connector. But it's also stopped working since, then came back to live. Perhaps there was some residual water somewhere.

This is why I took the speed sensor out, in attempt to clean it and dry it out. I was more concerned about the state of the gearbox after finding gear oil on the sensor.

Thanks for your reply.
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Re: Oil on speed sensor

Post by brinkie » Wed Aug 30, 2017 10:25 am

The ECU has NOTHING to do with intermittent failures of the speedometer. Only the 2 litre engine has a feed from the speedometer to the ECU, to signal the ECU that the car is driving, but without this feed the car runs just fine and so does the speedometer. If the engine cuts out when driving to a junction, you should be looking at the idle control valve rather than the wiring. If there was moist in the connectors, a hot engine on a summer day dried pretty much all the water that came in.
The sensor can be completely submerged in water or oil and still function. There is no active (i.e. powered) component. It is just a bunch of wires. By taking the sensor out, you could have damaged the wiring, though.

The ECU is next to the footwell inside the passenger compartment, if driving through deep water has damaged it and/or affected the connectors, you must have had soaking wet feet. :lol:

Measure with an ohmmeter across pins 6 and 12 of the grey connector in the dashboard (once you have taken the instrument cluster out), you should measure 3 ohms there.
Clean out the idle control valve with brake cleaner or carburettor cleaner (anything that dissolves the goo that builds up inside the valve)
Check all the equipment that is being fed with the same fuse as the radio. If those do function while the radio does not, the problem is in the radio or the connector behind it.

I think you are looking at three totally unrelated problems, which might have been caused by taking some connectors apart, but then again, they might have not!
Robert.

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Re: Oil on speed sensor

Post by 89of480 » Sat Apr 14, 2018 3:54 am

brinkie wrote:
Wed Aug 30, 2017 10:25 am
The ECU has NOTHING to do with intermittent failures of the speedometer. Only the 2 litre engine has a feed from the speedometer to the ECU, to signal the ECU that the car is driving, but without this feed the car runs just fine and so does the speedometer. If the engine cuts out when driving to a junction, you should be looking at the idle control valve rather than the wiring. If there was moist in the connectors, a hot engine on a summer day dried pretty much all the water that came in.
The sensor can be completely submerged in water or oil and still function. There is no active (i.e. powered) component. It is just a bunch of wires. By taking the sensor out, you could have damaged the wiring, though.

The ECU is next to the footwell inside the passenger compartment, if driving through deep water has damaged it and/or affected the connectors, you must have had soaking wet feet. :lol:

Measure with an ohmmeter across pins 6 and 12 of the grey connector in the dashboard (once you have taken the instrument cluster out), you should measure 3 ohms there.
Clean out the idle control valve with brake cleaner or carburettor cleaner (anything that dissolves the goo that builds up inside the valve)
Check all the equipment that is being fed with the same fuse as the radio. If those do function while the radio does not, the problem is in the radio or the connector behind it.

I think you are looking at three totally unrelated problems, which might have been caused by taking some connectors apart, but then again, they might have not!
Sorry to revive an old thread! But I am having a real headache trying to get my speedometer working! I have tried two different clusters; Both were known to work before and now one does not work, and neither does the odometer, and the second one (the main one I’ll be sticking with) the odometer has been witnessed working; but the strangest thing is the operation of the speedometer! Sometimes it will bounce around if the car is moving, or even if the car is not moving, sometimes it will work for a short while and bounce around a little bit, but most of the time it does nothing. I have resoldered the connectors on the back of the cluster with no luck, does this sound likely that there is a problem with the sensor itself? It is a replacement part I ordered online from a breaker, however the plug had been cleverly cut off, so we had to use the old connector plug from my old sensor. The cable is also longer than factory now too. Is it likely another replacement speed sensor is required? I’m a bit unsure of what to make my next move now!

Thank you!
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Re: Oil on speed sensor

Post by brinkie » Fri Apr 27, 2018 1:44 pm

It's a good thing the connector has been cut, because that is probably the source of your problems!
First measure the sensor across the wires with an ohmmeter, it should read around 3 ohms.
Then cut off all connectors, and solder the wires. If the problem persists, run a pair of wires from the speedometer sensor to the instrument cluster. This way I have fixed my speedometer and it hasn't failed ever since!
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
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Re: Oil on speed sensor

Post by 89of480 » Sat Apr 28, 2018 8:46 am

brinkie wrote:
Fri Apr 27, 2018 1:44 pm
It's a good thing the connector has been cut, because that is probably the source of your problems!
First measure the sensor across the wires with an ohmmeter, it should read around 3 ohms.
Then cut off all connectors, and solder the wires. If the problem persists, run a pair of wires from the speedometer sensor to the instrument cluster. This way I have fixed my speedometer and it hasn't failed ever since!
Thank you very much my friend! I will make this my mission for today! :)
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Re: Oil on speed sensor

Post by 89of480 » Sun Apr 29, 2018 12:04 am

brinkie wrote:
Fri Apr 27, 2018 1:44 pm
It's a good thing the connector has been cut, because that is probably the source of your problems!
First measure the sensor across the wires with an ohmmeter, it should read around 3 ohms.
Then cut off all connectors, and solder the wires. If the problem persists, run a pair of wires from the speedometer sensor to the instrument cluster. This way I have fixed my speedometer and it hasn't failed ever since!
I checked the resistance earlier today, I got a reading of 1.9Ω off of the sensor at the connector; I cut the cable as close to the sensor as I could and I still got 1.9Ω. I have joined the cable again now without the connector, and I will see if this works, I have already soldered the back of the speedometer so hopefully this will fix my problems! Unfortunately I won’t get a chance to check yet but I hope this will solve it!
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Re: Oil on speed sensor

Post by brinkie » Sun Apr 29, 2018 10:11 am

How much resistance do you measure when you are simply holding the pins of the measuring probes together? It might well be that the sensor is short-circuited.

Also, it's too late now, but there was no reason to cut off the entire cable, just the connectors would have been enough.
Robert.

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Re: Oil on speed sensor

Post by 89of480 » Sun Apr 29, 2018 11:06 am

brinkie wrote:
Sun Apr 29, 2018 10:11 am
How much resistance do you measure when you are simply holding the pins of the measuring probes together? It might well be that the sensor is short-circuited.

Also, it's too late now, but there was no reason to cut off the entire cable, just the connectors would have been enough.
The measuring probes were giving me a dead short of 0 when I held just them together, but yes on the sensor I was reading 1.7, 1.8 and finally 1.9.
Yeah I realised that once I had cut the cable, although at the time my thought process was to cut it short to make sure there weren’t any breaks in the wire :lol:
However, the car is drying out at the moment inside, along with all the carpet and foam, so I won’t be able to check for a week or two, but I fear the sensor may be short circuiting too. Perhaps it’s time to try and trace a spare? :(
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Re: Oil on speed sensor

Post by brinkie » Sun Apr 29, 2018 6:16 pm

I have tested my spare sensor: 1.9 ohm. So that looks normal.
I don't know if you have access to a portable oscilloscope? Once the circuit is complete, the speedometer sends a signal of approximately 125 kHz across the sensor (actually the sensor is part of an oscillator). This way I am testing speedometers in situ without the need of a test drive. If the signal is present, everything works.
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Re: Oil on speed sensor

Post by 89of480 » Tue May 01, 2018 1:55 am

brinkie wrote:
Sun Apr 29, 2018 6:16 pm
I have tested my spare sensor: 1.9 ohm. So that looks normal.
I don't know if you have access to a portable oscilloscope? Once the circuit is complete, the speedometer sends a signal of approximately 125 kHz across the sensor (actually the sensor is part of an oscillator). This way I am testing speedometers in situ without the need of a test drive. If the signal is present, everything works.
I think we do actually have an oscilloscope somewhere, that’s a very clever way of you checking!

Knowing that your spare sensor gives a reading of 1.9Ω makes me feel much more confident. Hopefully the problem will just be that connector between the speedometer and the sensor, which I have now removed and I’m waiting for access to the car again to try it, I’m really hoping so, given that I tried 2 known working speedometers and still got nothing. So I will let you know as soon as I have tested it! Thank you!!!
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Re: Oil on speed sensor

Post by brinkie » Tue May 01, 2018 12:06 pm

89of480 wrote:
Tue May 01, 2018 1:55 am
I think we do actually have an oscilloscope somewhere, that’s a very clever way of you checking!
If you also have an audio signal generator, just hook it up to the terminals and apply a 400 Hz signal to test the speedometer. Your speedometer should show around 120 mph.
An Android phone will act nicely as signal generator, I am using an app called "Simple tone generator" (type 400 and then turn up the volume to max), but there are plenty other apps available. Use an audio cable with a 3.5mm jack connected to the phone and use something like crocodile clips to attach the speedometer signal cable to the phone.
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
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Re: Oil on speed sensor

Post by 89of480 » Wed May 02, 2018 12:33 am

brinkie wrote:
Tue May 01, 2018 12:06 pm
89of480 wrote:
Tue May 01, 2018 1:55 am
I think we do actually have an oscilloscope somewhere, that’s a very clever way of you checking!
If you also have an audio signal generator, just hook it up to the terminals and apply a 400 Hz signal to test the speedometer. Your speedometer should show around 120 mph.
An Android phone will act nicely as signal generator, I am using an app called "Simple tone generator" (type 400 and then turn up the volume to max), but there are plenty other apps available. Use an audio cable with a 3.5mm jack connected to the phone and use something like crocodile clips to attach the speedometer signal cable to the phone.
It’s crazy how you come up with all of these ideas! I find it truly fascinating, I love it! Even if speed sensor is working now after removing the connector I want to try this just to see it actually working!

I also found your YouTube channel last night; plenty of interesting stuff on there! Watching that headlight continuously spin round reminded me one of my headlights is lower down than the other when they are shut :?
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Re: Oil on speed sensor

Post by brinkie » Thu May 03, 2018 8:36 am

When the 480 could still be ordered new at the Volvo dealerships, I was getting a degree in electronic engineering, so I have learned a thing or two about how stuff works. :lol:
Robert.

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Re: Oil on speed sensor

Post by 89of480 » Thu May 03, 2018 10:44 pm

brinkie wrote:
Thu May 03, 2018 8:36 am
When the 480 could still be ordered new at the Volvo dealerships, I was getting a degree in electronic engineering, so I have learned a thing or two about how stuff works. :lol:
Very nice, lucky you! What a fantastic skill!! :D

I wish I could of been old enough to buy one at the time they were still new, that would of been very nice! I would of loved to of purchased a brand new Celebration kept it myself the whole time :wink:

I will definitely let you know how the speed sensor goes!! Thank you very much for your help!
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Re: Oil on speed sensor

Post by brinkie » Tue May 08, 2018 3:02 pm

I got my drivers license in 1989 and got my B.Sc. in electronic engineering in 1994, but I really had no money for a Volvo 480. Should have studied for general manager or something in marketing and sales instead of learning a skill, that would have paid better :lol:
Robert.

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Re: Oil on speed sensor

Post by 89of480 » Tue May 15, 2018 2:09 pm

brinkie wrote:
Tue May 08, 2018 3:02 pm
I got my drivers license in 1989 and got my B.Sc. in electronic engineering in 1994, but I really had no money for a Volvo 480. Should have studied for general manager or something in marketing and sales instead of learning a skill, that would have paid better :lol:
But skills are valuable, the fact you studied all of this is impressive enough!

Besides, you helped me get the speedo working! :hopping:

Image

I can’t thank you enough, I cut the connector off and found the screened cable broken too, so now I’m very happy!!! :rofl:
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Re: Oil on speed sensor

Post by brinkie » Wed May 16, 2018 7:15 am

Cheers mate! :wave:
Robert.

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