Aftermarket Coolant Temperature Sensor/ Sender Part Number

[Martin]

Gryph tell me where I can get one for $10.00-$15.00 more in a week in OZ, really no cheap anything in OZ. Have not seen one on Ebay or Gumtree for ages very little available especially for K75's. You guys are spoiled for choice, most of the time it is far cheaper for us to source from overseas. I am attempting preempt parts failure and get a stock of parts that are getting harder to get. Even I'm not in a bad position compared to some as I have a source of loaner parts from a mate. An acquaintance with a couple of bricks rang me the other day urgently chasing a rear master cylinder, I sold him my spare Chinese one for cost. As Bricks age it is going to get harder to source parts to keep them on the road. Alternatives needs to be sourced. So far I'm happy with my Chinese GPS, Master cylinder, and fuel pump. Occasionally I will probably get a dud I am willing to deal with it.
Regards Martin.

[Laitch]

Occasionally I will probably get a dud I am willing to deal with it.

And so you should, living in Paradise and all.  :giggles

[Martin]

Paradise and my éclairs don't suffer from frostbite, unlike your profiteroles.  :hehehe
Regards  a warm and contented Martin.

[kris]

Parts jobbers in my neck of the woods want CDN $50 for the temp sensor. Sometimes it is better to shop locally. Even if I see one for USD 25 I have to pay a 30 per cent exchange rate and then shipping fees anywhere from USD 15 to 50 to get it into Canada. I kid you not....some of the shipping quotes are ridiculous! So, as much as the initial Canadian price looked stupid, it turns out it might have been the smartest choice in the end. And I can drive down and pick it up in 10 minutes....cost/ benefit, eh?

[Martin]

I borrowed a OEM sensor of a mate.  I connected a multimeter to the terminals on the OEM one and sat it in boiling water and recorded the results every time time the water decreased by 5C. I did the same with the  two aftermarket ones and recorded the results and allowing for slight discrepancies the results were virtually identical. Can Rob or Inge or anybody answer the following questions, if the readings are the same for any given temperature why won't the aftermarket ones work? What is the purpose of it earthing through the sensors body? I was going to test all the sensors again but my new digital temperature gauge crapped out. I'll take it back to Jaycar tomorrow.  I am getting to the stage where I might just fit one and see what happens, probably next weekend should only take 1-2 hours. Once I run the temperature test again I'll post the results. I don't believe the graph that I posted is for the 2v Brick.
Regards Martin.

[Inge K.]

Can Rob or Inge or anybody answer the following questions, if the readings are the same for any given temperature why won't the aftermarket ones work?

If the Reading from each terminal to the housing is the as the OEM 2V sensor it should work.

What is the purpose of it earthing through the sensors body?

That is how the analouge Jetronic is designed to read the sensor value.
Motronic is digital and sends out a 5V+ signal which Returns via the second sensor terminal,
the motronic reads the voltage drop as the actuall value.

I don't believe the graph that I posted is for the 2v Brick.

It's for the 2V models and is from the troubleshooting guide at the K100 forum, and have helped many
members during the years it have existed.

[rbm]

If the temperature response curve is the same as OEM and the electrical connections inside the sensor are the same as OEM and the physical dimensions are the same as OEM, then it should work.

The 2V temp sensor in the stand pipe on the left side of the engine consists of two separate resistors with a common connection shared between them.  Each remaining end of the resistors (there are 2) will terminate at the spade lugs. The common connection goes to the body of the sensor.  That's why the sensor has to ground out through the body; so that electrically the common point is referenced to ground.  With this sensor, Bosch are producing a 3-terminal device in a package containing only 2 terminals.  Most other temp sensors have only one resistor inside (including the one used on the 4V Motronic models) where each end of the resistor terminates in the spade lugs .  The body is electrically isolated and therefore will not function with the L-Jetronic.

[Martin]

Thanks Rob I appreciate picking your brain. If I can free up enough time I might try and fit the new one today, if not next weekend. If I do fit it I will put the OEM one in the tail unit, although besides the power supply for the GPS nothing else Chinese has failed.  I am looking at getting a set of spare HES's and guess where they are made. The way I am going I might have to join the Chang Jiang forum and change the badges.     :hehehe    What scale should I be setting my multimeter on when testing the sensor, I have been setting it on 20k.  :dunno
Regards Martin.

[Martin]

Decided to bite the bullet and fit one, they don't work. The engine immediately floods. I took a shortcut when fitting it, I removed the MAF and went in that way. So the job will take about two hours.
Regards Martin.

[Inge K.]

When the sensor don't have any ground connection the Jetronic unit reads it as infinite resistance to ground,
and think that it's very damn cold indeed.

[Martin]

Thanks Inge least I know they don't work. I'm trying to find another cheap source of one that works. A mates son who works for a large auto electrical company and is looking for a cheaper alternative. :dunno The process at least allowed me to clean the OEM one properly. The contacts were pretty grungy and required scraping as well as using DeoxIT.  :2thumbup:
Regards Martin.

[szabgab]

Inge they are going to test the sensor before they send it. For $10.00 I am willing to do the research. It also might be possible that it was just a faulty sensor as there was the same resistance readings between the spade connectors on a known good OEM one and the Chinese one. :dunno If the new one is good, it will be a good result for all inmates as they are ultra cooperative and quick in answering any concerns, they appear at this stage to be legit.
Regards Martin.

Edit - sorry, I have just realised, the topic is spanning two pages, I have read only the first one.... So now realising, Martin did not succeed with the Chinese alternatives, I suppose it is time to source one from breakers... Or try to clean the one in the bike :)

Hi guys, sorry to retrieve an old topic... I am having 'trouble' cold starting the bike - meaning even in 30C summer my 75S needs choke for it's first start, or a start of a partially cooled down bike (like half an hour after a longish city ride in the summer heat with the fan kicking in a few times). I have replaced the fuel filter, but that made matters even worse, bike now most definitely needs a choke, otherwise it will not even start and needs it on for 5-10 minutes, otherwise idle is 5-600RPM. Bike otherwise rides like a champ, so next in line will be water temp sensor, am I right?

[alabrew]

A new one didn't fix the cold start issues on my "85, still trying to figure it out.
Fuel economy is poor too which is wierd as it feels like it isn't getting fuel when cold.
Hot is pretty good. It can get too hot and then it bucks.

[daveson]

Hi Gabe

Maybe test it before replacing it.

Since Europe is having an Australian summer this year, for comparison I never need the choke and the fan very rarely comes on.

I have a vague memory that you altered the air/fuel ratio and maybe even the airflow meter vane. Excessive need of choke and overheating point to lean mixture as a possibility. Parts not measured by the coolant sensor may be overheating. Consider returning stuff back to factory settings. You can guess my other guess causing a lean mix.

[Scott_]

I'll just throw out a little reminder here, though you probably all know it, these fuel injected bikes don't have a "choke".... per se, it is only a throttle advance.
The term "choke" was a hold over from the carburated bikes that actually did have a choke butterfly plate in them.

I return you now to regular programming.

[szabgab]

Guys, thank you for your replies and sorry to first retrieve and subsequently hijack this thread...

A new one didn't fix the cold start issues on my "85, still trying to figure it out.
Fuel economy is poor too which is wierd as it feels like it isn't getting fuel when cold.
Hot is pretty good. It can get too hot and then it bucks.

Same here. Fuel economy is poor-ish (although summer brought with it a bit better consumption). Lean mixture causes crap fuel economy too, as the engine is not working as efficiently as it should. I do not have a CO tester, neither do the mechanics I know around here, but the MOT stations do, so I might just pay them some dough to try to get a proper mixture

Hi Gabe

Maybe test it before replacing it.

Since Europe is having an Australian summer this year, for comparison I never need the choke and the fan very rarely comes on.

I have a vague memory that you altered the air/fuel ratio and maybe even the airflow meter vane. Excessive need of choke and overheating point to lean mixture as a possibility. Parts not measured by the coolant sensor may be overheating. Consider returning stuff back to factory settings. You can guess my other guess causing a lean mix.

Dave - Good point on testing, I did that, when I first got the bike, but Laitch was suggesting testing the sensor at the sensor itself and not at the computer, as I did it, so I guess it is time to do it that way. I did not touch the mixture setting, neither the vane, I think Soggz was having a go at something like that. I still might have a lean mixture though, however the new fuel filter should have made the mixture richer, not leaner, I'd guess.

[daveson]

Too right,  my brain went AWOL on the choke and the bike.

But I do remember that you replaced the injectors, then your headers turned blue.  To me that presents a clear and present danger, requiring action. It points to a lean mix,  causing overheating. Maybe disable the coils and check the injectors spray pattern, maybe volume too.

Some of your other symptoms were contradictory, if you made some changes maybe go back to factory settings.

Sounds like you need another fuel filter, sometimes a new one is bad if the sealing caps were loose,  cracked or missing.

Your other high idle problem maybe also points to a lean mix. Reducing the idle speed masks the problem, applying the "choke" overcomes the mask.

Maybe.

[szabgab]

Too right,  my brain went AWOL on the choke and the bike.

But I do remember that you replaced the injectors, then your headers turned blue.  To me that presents a clear and present danger, requiring action. It points to a lean mix,  causing overheating. Maybe disable the coils and check the injectors spray pattern, maybe volume too.

Some of your other problems were contradictory, if you made some changes maybe go back to factory settings.

Your other high idle problem maybe also points to a lean mix. Reducing the idle speed masks the problem, applying the "choke" overcomes the mask.

Maybe.

Dave, you are right, my high idle was masking a problem, a not perfectly balanced TB. Since then I have lowered the idle to 900-950 and re-balanced the whole shebang, now my bike idles very happily at those RPM's. Injectors are the same, however I have replaced the cracked one with a known good one, my headers are normal colour now, plugs look perfect. I have bored myself to death with the OCD I have, but I keep soldiering on :D