Official s52 temp sensor without tapping the head thread

[equate975]

Ok, well I am going to figure out how to do this without tapping the head.

This is what I got for ohm readings and other misc info that might be helpful

e36

EDIT: that info on here was the damn IAT sensor..

e30

s14

2k ohms at 25 cel
1568 ohms at 31 cel

m20

91 F low speed fan kicks on
99 F hign speed fan kicks on

m10

GAUGE READINGS!!!
Coolant temp (F) Gauge sensor (ohms)
186 64
166 73
161 87
145 126
137 143
122 200
107 267
99 309
89 367
81 440

Part Numbers

m10

04 TEMPERATURE-TIME SWITCH 35CEL 8S 13621274630 $72.54
06 TEMPERATURE SENSOR, WATER 20CEL 2500 OHM 13621357414 $44.36
08 TEMPERATURE SENDING UNIT/WARNING CONTACT 45CEL 12621285073 $64.17



m20

12 ENGINE COOLANT TEMP SENSOR 1-POL 1 12621710512 $17.52
13 TEMPERATURE SENSOR, WATER 20CEL 2500 OHM 13621357414 $44.36



s14

05 TEMPERATURE SENSOR M12X1,5 13621709966 $32.36
07 ENGINE COOLANT TEMP SENSOR 1-POL 12621710512 $17.52


s52

14 DOUBLE TEMPERATURE SWITCH 13621703993 $19.75 +core

If anyone can find some more ohm info so I can find the right setup post it up. I dont have a bently for every BMW :)

[The Fast One!]

I was pretty sure there was a way to do it by just splicing some wires.

but if you can figure this out it would be great.

[equate975]

I was pretty sure there was a way to do it by just splicing some wires.

but if you can figure this out it would be great.

No that splicing wire guide for the OBDI conversion is assuming the engine is going into an e36, which its not. There for the temp gauge dosnt work.

[equate975]

Got my hands on a s14 gauge temp sender. If I can get it to work I can whip something up for you m20 guys.

[FredK]

Great! Hopefully we can get an idea of what might and what might not work for this sensor!

[Vass325es]

Restless to hear how do that..

[equate975]

Update, got readings for a 318i!!

[FredK]

Both of the sensors are NTC thermistors. The two variables that affect sensor output are the values of Beta (in K) and the resistance at room temperature (R25C).

My calculated Beta for the M10 sensor is 3300K, and R25C is 473 ohms. In order to see if the system can be "faked" using a resistor, we're going to need resistance vs. temperature data for the M50 sensor. If the values of Beta match, then all we'll need is a resistor placed in series that is fairly well isolated from the engine compartment (i.e. inside the glovebox).

If you have one lying around I could do the experimentation if you send it to me. Otherwise, you're just going to have to put the sensor into different temperature water and measure the resistance.

[equate975]

Both of the sensors are NTC thermistors. The two variables that affect sensor output are the values of Beta (in K) and the resistance at room temperature (R25C).

My calculated Beta for the M10 sensor is 3300K, and R25C is 473 ohms. In order to see if the system can be "faked" using a resistor, we're going to need resistance vs. temperature data for the M50 sensor. If the values of Beta match, then all we'll need is a resistor placed in series that is fairly well isolated from the engine compartment (i.e. inside the glovebox).

If you have one lying around I could do the experimentation if you send it to me. Otherwise, you're just going to have to put the sensor into different temperature water and measure the resistance.

That was my entire idea...

I dont have sensor on hand right now is the problem. I am getting a s14 sensor shipped in for me, but this wont help you m20 guys.

And you would need to measure the s52 sensor not m50

[equate975]

We are fucked

I was hoping the ohm to temp relationship would be liner, but its not...

Which means adding a resistor or anything isn’t going to work. The only way that would make the e30 gauge work with the s52 sensor would be to program a PIC or something to do the conversions. And since accurate data sheets with the mathematical information on this don’t seem to exist, it does not seem worthwhile to waste my time doing it.

It would be much more efficient, cheaper, and better just to tap a new vdo gauge in there.

HOWEVER

I am wondering if the e36 m3 GAUGE will work, instead of messing with the sensor im going to try and swap gauges. Hopefully, the wires going to the gauge don’t have a resistor, or some sort of module they go through to change the value.

[FredK]

Don't abandon hope!

The ohm to temp relationship shouldn't be linear for a thermistor. The M10 data you posted shows that the resistance drops off very quickly as the temperature increases from room temperature, but much slower when the temperature gets higher, i.e. it shows a logarithmic response. Plotted on a semi-log plot, the data is linear. I see no reason why the response would be different, only the values should be different.

Can you post the data, so I can see if I can make heads or tails of it?

[equate975]

I was just testing the m20 temp sensor now when I realised it.

If its not linear its not worth fucking with. The only way to make a stock gauge work would to make a PIC processing unit of some fashon to do the math. Which would take time to figure out and at the cost of tapping the head or setting up a VDO system its not worth the money or the time when you can have something better cheaper.

[Skafrog]

What is wrong with tapping the head? It's not hard.

[equate975]

Nothing, I was just trying to find a way around it to add another option.

Now, do I pop the head and drill.. or just drill the fucker and hope I dont get too many metal shavings in my coolant :P

[sushipower]

Nothing, I was just trying to find a way around it to add another option.

Now, do I pop the head and drill.. or just drill the fucker and hope I dont get too many metal shavings in my coolant :P

Anyone has before and after pics??