Post by crogthomas on May 14, 2023 9:34:30 GMT 1
A few posts recently have been asking about M10 threaded temperature sensors for the LC and YPVS, and since I too have been looking for one I thought I’d share what I have found. Some of this is from experience and measurements I have taken, other parts are from knowledge I have found on this very forum. It’s possible some of it is wrong, so if anything looks off, let me know and I will dig deeper. Every day is a school day.
The short version of what I’ve found is to search for a VDO sensor, part number 323-801-005-005D.
There are three aspects to the temperature sensor to make sure it is suitable. The thread, connector and resistance.
Thread
RD350LC 4LO used a M10 x 1.0mm thread. I assume the 250 the same.
The 31k YPVS (LC2 and F1/N1 with heads marked Y1 and Y2) started with a M10 thread the same as the LC, but it seems that later YPVS (F2/N2 & R, with heads marked Y3) changed that to a 1/8NPT thread, which is quite a common one used on lots of aftermarket sensors and other Yamaha models.
Edit to add: Some Y2 heads appear to have a M10 thread and some a 1/8 NPT thread.
The M10 is a parallel thread which means it needs a sealing washer.
The 1/8NPT is a taper thread which means it seals by wedging the threads together until there is no space left. A NPT thread should have some sort of sealant (PTFE tape or paste) to achieve this properly.
A 1/8NPT thread is close enough to M10 in diameter and pitch that it is possible to force it into a M10 threaded cylinder head. It will distort the threads in the head. I wouldn’t, but lots of people do it successfully.
Connector
The original LC and YPVS sensors both had a 4.8mm spade terminals, not the more familiar 6.35mm ones. The smaller size is available though if you need to repair a loom to match a standard sensor.
At the same time as the thread changed M10 to 1/8NPT, the connector also changed to a bullet type connector.
Since there don’t appear to be many alternative temperature senders available and the wiring is the simplest thing to adapt, many people simply make up a short length of wire with suitable connectors on each end to match the sensor and the loom that they have.
Resistance
To read correctly the resistance of the sensor needs to be correct at the relevant temperatures. I suppose it is not that critical, the temperature gauges are not marked with numbers. All that it really needs to show is when the bike it up to temperature and if it is overheating. I’m willing to bet that the gauges or the sensors are not particularly accurately made anyway.
I can’t recall where I found this image, but it shows the approximate temperatures of each point on the LC2 temperature scale.
LC2tempGauge by crogthomas, on Flickr
The YPVS Haynes manual gives test resistances for the sender at different temperatures.
HaynesTempSenderTest by crogthomas, on Flickr
With this information it is easy enough to check both gauges and sensors are working correctly. It’s also possible to use this information to find alternative sensors.
I tested a couple of spare LC2 gauges and a F2 one using a resistance box, and got close to what the Haynes manual says, with some variation, 10 ohms either way. Not bad for 30 year old gauges.
20230326_105423 by crogthomas, on Flickr
OEM Sensors
All of the currently available replacement sensors are the 1/8NPT type with the bullet connector, Yamaha (11H8359100), Yambits, Norbo all can get them. They seem to be a common part for many Yamahas, even as recently as the R6. (I say recent, the 5EB is over 20 years old)
The M10 part (5R28359100) is no longer available, and even if it were, it would be a wallet lightening £70. Ooooffff.
Alternative options
Many but not all aftermarket accessory gauges and senders for boats and trucks tend to follow the VDO ‘standard’ of 40-120 degrees C equating to 287-23 ohms. Confirming this is tricky, as occasionally a gauge manufacturer will use something completely different for no apparent reason, but most seem to match. Handily this very closely matches the YPVS gauge/sender resistance ranges, so generally anything listed as being 40-120 degrees C, VDO compatible should work. If it says 40-150 degrees C then it is an oil temperature sensor, which have different resistance ranges and therefore won’t be suitable.
VDO do provide all the technical specs on their website and the catalog suggests a few sensors that would be a good match, except for the connector. Most of the VDO sensors use a disc type connector with is supposed to be used with the same type of 6.35mm connector as a blade. It might be possible to turn it down in a lathe or file it smaller so that it can be used with the standard 4.8mm connector on the loom.
There is also a Smiths sensor that should work. This one has a blade terminal, but again a 6.35mm one, so it could either be modified with a file, or a conversion cable made up.
I looked through some car parts catalogues for sensors with a suitable M10 thread, in the hope that I might find something more easily available. The catalogues unfortunately rarely give the actual resistances and most OEMs seem to pick resistance ranges entirely at random. However I found a couple that I decided might be worth trying, so ordered them to give them a go. I also ordered the commonly used Landrover sensor (which has a 1/8 NPT thread), just to confirm its resistance range.
I tested the sensors I ordered, plus a bunch of standard Yamaha sensors I had laying about, in a pan of water on the stove to confirm their ranges. This is surprisingly difficult to do accurately because there is a long delay in the reading due to the body of the sensor taking time to reach the same temperature as the water, by which point the water may have changed temperature. I took measurements both whilst heating up and cooling down the water to get an average.
Left to right, VW (disc), Landrover (bullet), Ford (blade).
20230402_124328 by crogthomas, on Flickr
Findings:
I may as well include the ones that don’t work, for future reference.
This last one seems to be the best option if you wanted to be kind to the M10 thread in your LC or 31k head. Searching online for the part number shows a few places where you can find one for less than £20.
I've not ordered one yet, but if someone else does, let us know how well it works, or not!
The short version of what I’ve found is to search for a VDO sensor, part number 323-801-005-005D.
There are three aspects to the temperature sensor to make sure it is suitable. The thread, connector and resistance.
Thread
RD350LC 4LO used a M10 x 1.0mm thread. I assume the 250 the same.
The 31k YPVS (LC2 and F1/N1 with heads marked Y1 and Y2) started with a M10 thread the same as the LC, but it seems that later YPVS (F2/N2 & R, with heads marked Y3) changed that to a 1/8NPT thread, which is quite a common one used on lots of aftermarket sensors and other Yamaha models.
Edit to add: Some Y2 heads appear to have a M10 thread and some a 1/8 NPT thread.
The M10 is a parallel thread which means it needs a sealing washer.
The 1/8NPT is a taper thread which means it seals by wedging the threads together until there is no space left. A NPT thread should have some sort of sealant (PTFE tape or paste) to achieve this properly.
A 1/8NPT thread is close enough to M10 in diameter and pitch that it is possible to force it into a M10 threaded cylinder head. It will distort the threads in the head. I wouldn’t, but lots of people do it successfully.
Connector
The original LC and YPVS sensors both had a 4.8mm spade terminals, not the more familiar 6.35mm ones. The smaller size is available though if you need to repair a loom to match a standard sensor.
At the same time as the thread changed M10 to 1/8NPT, the connector also changed to a bullet type connector.
Since there don’t appear to be many alternative temperature senders available and the wiring is the simplest thing to adapt, many people simply make up a short length of wire with suitable connectors on each end to match the sensor and the loom that they have.
Resistance
To read correctly the resistance of the sensor needs to be correct at the relevant temperatures. I suppose it is not that critical, the temperature gauges are not marked with numbers. All that it really needs to show is when the bike it up to temperature and if it is overheating. I’m willing to bet that the gauges or the sensors are not particularly accurately made anyway.
I can’t recall where I found this image, but it shows the approximate temperatures of each point on the LC2 temperature scale.
LC2tempGauge by crogthomas, on Flickr The YPVS Haynes manual gives test resistances for the sender at different temperatures.
HaynesTempSenderTest by crogthomas, on FlickrWith this information it is easy enough to check both gauges and sensors are working correctly. It’s also possible to use this information to find alternative sensors.
I tested a couple of spare LC2 gauges and a F2 one using a resistance box, and got close to what the Haynes manual says, with some variation, 10 ohms either way. Not bad for 30 year old gauges.
20230326_105423 by crogthomas, on FlickrOEM Sensors
All of the currently available replacement sensors are the 1/8NPT type with the bullet connector, Yamaha (11H8359100), Yambits, Norbo all can get them. They seem to be a common part for many Yamahas, even as recently as the R6. (I say recent, the 5EB is over 20 years old)
The M10 part (5R28359100) is no longer available, and even if it were, it would be a wallet lightening £70. Ooooffff.
Alternative options
Many but not all aftermarket accessory gauges and senders for boats and trucks tend to follow the VDO ‘standard’ of 40-120 degrees C equating to 287-23 ohms. Confirming this is tricky, as occasionally a gauge manufacturer will use something completely different for no apparent reason, but most seem to match. Handily this very closely matches the YPVS gauge/sender resistance ranges, so generally anything listed as being 40-120 degrees C, VDO compatible should work. If it says 40-150 degrees C then it is an oil temperature sensor, which have different resistance ranges and therefore won’t be suitable.
VDO do provide all the technical specs on their website and the catalog suggests a few sensors that would be a good match, except for the connector. Most of the VDO sensors use a disc type connector with is supposed to be used with the same type of 6.35mm connector as a blade. It might be possible to turn it down in a lathe or file it smaller so that it can be used with the standard 4.8mm connector on the loom.
There is also a Smiths sensor that should work. This one has a blade terminal, but again a 6.35mm one, so it could either be modified with a file, or a conversion cable made up.
I looked through some car parts catalogues for sensors with a suitable M10 thread, in the hope that I might find something more easily available. The catalogues unfortunately rarely give the actual resistances and most OEMs seem to pick resistance ranges entirely at random. However I found a couple that I decided might be worth trying, so ordered them to give them a go. I also ordered the commonly used Landrover sensor (which has a 1/8 NPT thread), just to confirm its resistance range.
I tested the sensors I ordered, plus a bunch of standard Yamaha sensors I had laying about, in a pan of water on the stove to confirm their ranges. This is surprisingly difficult to do accurately because there is a long delay in the reading due to the body of the sensor taking time to reach the same temperature as the water, by which point the water may have changed temperature. I took measurements both whilst heating up and cooling down the water to get an average.
Left to right, VW (disc), Landrover (bullet), Ford (blade).
20230402_124328 by crogthomas, on FlickrFindings:
I may as well include the ones that don’t work, for future reference.
- VW part no. 035919501, M10 thread but totally wrong resistance range.
- Intermotor part no. 53018, Ford Galaxy, M10 thread but totally wrong resistance range.
- LandRover part no. AMR1425, 1/8NPT thread, bullet connector, close in resistance, 40 ohms at 100C.
- Smiths TT3001-M10, M10 thread, 6.3mm blade connector, a good match in resistance according to the spec. Not tested.
www.smiths-instruments.co.uk/sender-units/temperature-senders - VDO 323-801-005-005D, M10 thread, 6.3mm disc connector, a good match in resistance according to the spec. Not tested.
vdo-webshop.nl/en/temperature-sensors/437-vdo-coolant-temperature-sender-120c-m10-4103590949271.html
This last one seems to be the best option if you wanted to be kind to the M10 thread in your LC or 31k head. Searching online for the part number shows a few places where you can find one for less than £20.
I've not ordered one yet, but if someone else does, let us know how well it works, or not!
