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I can’t help you with your dodge van but if you had a ford I’m already doing exactly what you want to do but with more sensors. If you tap into an existing sensor and don’t load it down it won’t effect the sensors reading, I’m doing this by running it into the Analog to digital converter of an Arduino.
This is an interesting idea, though I’m not sure on a timeline for it. I’ve never made my own electronics before so that’ll probably take me a while.
I’m thankful for all the discussion/contributions at this point. It’s conversations like this that get the boilers in my brain fired up - I’ll just need to let the steam vent until I’m ready to act on it.
most all TFT's I have seen are just simple NTC type Thermistors... they are wired in a Voltage divider configuration... and the Electronics in the Computer reads a change in Voltage and that is the Raw Data (Voltage) you can read across it with a voltmeter without changing the data Providing your Voltmeter has High enough input Impedance to not Load the circuit.
most all TFT's I have seen are just simple NTC type Thermistors... they are wired in a Voltage divider configuration... and the Electronics in the Computer reads a change in Voltage and that is the Raw Data (Voltage) you can read across it with a voltmeter without changing the data Providing your Voltmeter has High enough input Impedance to not Load the circuit.
I’ve spent more than 2 hours (collectively) reading everything I can find in service info about the operation of the transmission, hoping somewhere in there would be a clue as to the type of sensor it is. Nothing.
All I know for certain is that it’s integrated into the solenoid/pressure switch assembly that’s bolted onto the back side of the valve body. The wiring diagram shows “Trans Temp Sig” running from the box that’s supposed to represent the solenoid/pressure switch assembly to the PCM. There’s no symbols inside the box (which, to my understanding, means it’s a solid state device) indicating what type of sensor it is like you would see if it were just a stand-alone temp sensor.
well, as far as the E4OD as an example the TOT is located in the solenoid Pack.....
The TOT sensor is Pins 7 and 8 on the connector ......
Pin #8 is Signal Return and Pin #7 goes to the Pin #7 of the PCM in a 93 Diesel for this example....
Schematically speaking it looks like this.......
IF you monitor the Voltage on the High side of the sensor it will inversely follow the Temperature ie as Temp goes Up Voltage goes down.
SO to make sense out of the Voltage the easy thing to do is use an Inverting OP AMP to drive a Digital Panel Meter (or and Analog Volt meter)
Your VRef on the sensor is most likely 5 Volts DC .... what you need to know is what the Resistance Value of the Thermistor is at Room Temp ... Generally 25C would be the Room Temp and at that Temp would give lets say a resistance reading of 10K Ohms .... then this says you have a 10K NTC thermistor.. then you can use a set of standard Curves for a 10K thermistor and probably be close enough for Gov't Work Calibration... then you would adjust the Gain on the OP Amp to display an appropriate Voltage to read as temperature on your Volt meter.
OK here is an example of a 10K thermistor output table.... http://2avrmz2nom8p47cc28p2743e-wpen...stor_10K-2.pdf
Being that there are many types of NTC thermistors it is important to find the Resistance Value at 25C and then you can do the math or Plot a curve using know temperature steps..... for example how many Ohms when I put the thermistor in an oil bath that is 75C then 100C etc etc etc
not knowing What Transmission you are working with .... I can only give you general information as I don't know the Specifics of your sensor... I would have to do just as I explained to discover what it is if the Manufacture will not release the Data on their part.
why dont you just check it cold according to chart, your not wanting to spend any money, and chart is free, all the suggestions will require money spent to accomplish said task
you would probably be better off just using something like this and JB Weld the Probe to the back of the transmission Oil Pan where it will probably get just as hot as the fluid
There are plenty of other units with different ranges that you could choose from all based on same Technology
FleaBay, Aliexpress, and even Gearbest carry these things.
could/would you attempt to drill hole in center of cap, buy you a meat thermometer long enough to touch bottom of pan and mark thermometer according to chart, then you always know the temp as soon as you pop hood? drill in center and epoxy/JB weld it in
this video explains where to mark for correct reading
I’m not? Hmm.... it’s interesting you say that. Could you quote the post where I said that? It may have been my twin brother, Network Ned, posting on here and pretending to be me.
Originally Posted by torq'ta 5 8
could/would you attempt to drill hole in center of cap, buy you a meat thermometer long enough to touch bottom of pan and mark thermometer according to chart....this video explains where to mark for correct reading
I have considered something similar to the meat thermometer, but the reason why I’m not willing to do it is placement. The reason I want to tap into factory wiring is because the factory temp sensor is on the back side of the valve body - whether you agree with it or not, this is the position that Dodge decided is the most critical place for temp measurement. If I’m relying on a probe that’s placed anywhere else, I have to account for the temp difference in the level readings, and that would change every time I check it depending on how long it’s been driven and the ambient temperatures (summer temps vs winter temps).
I’ve also seen the video on the engine oil dipstick mod. I’m not saying he’s not right to have a hot and cold range, but to have an accurate hot check, you still need to know fluid temp and that’s all manufacturers, not just Dodge. The only point of the cold range is to know you have enough fluid to drive the vehicle safely until a hot check can be made.
Originally Posted by lonewolf_
you would probably be better off just using something like this and JB Weld the Probe to the back of the transmission Oil Pan where it will probably get just as hot as the fluid
There are plenty of other units with different ranges that you could choose from all based on same Technology
FleaBay, Aliexpress, and even Gearbest carry these things.
Lonewolf, I appreciate all the information you’ve shared. I’ll have to see how it works out for me when I have time.
To be honest, I’m surprised something like this doesn’t already exist given the variety of aftermarket gauges there are.
For the moment, I think I’m gonna have to shelf this idea. Besides the apparent time (which is hard for me to find these days) and effort it’s going to take to figure out how to make a gauge work as I want it to, I just answered my question in this post - I didn’t consider the warranty (until the meat thermometer idea).
I haven’t read all the fine print but I’m not gonna argue about covered repairs due to a simple tapping of a signal wire, so until the warranty is up, I guess I’ll be getting a small scan tool or phone adapter.
To be honest, I’m surprised something like this doesn’t already exist given the variety of aftermarket gauges there are.
I'll bet something like this doesn't exist because nobody wants to produce a product that potentially will cause a computer and/or transmission failure.
I'll bet something like this doesn't exist because nobody wants to produce a product that potentially will cause a computer and/or transmission failure.
I agree 100%... if anything was to fail in the Gauge circuit it could easily take out the PCM or the TFT/TOT ... not to mention Warranty Issues by just having it there.
different sensors create a calibration issue for a mass produced device too.
Always better to use a separate gauge circuit or just monitor the data stream in the case of OBD2
MY standard Disclaimer applies here.......
This information is provided free of charge and is probably worth precisely what you paid for it. If you build one of these devices, it is likely that it will fly apart and kill everyone within 5 blocks. Construct and use at your own risk.
post #9 3) If I wanted to purchase a small scan tool or OBD adapter for my phone to read live data, I would. But, I don’t want to, which is the reason for asking people who know more than me if this is a viable option. totally understand temp difference, but you dont know when the sensor will malfunction, I thought manual said drive/warm up 15 minutes, apply park brake, check in neutral, sensor in valve body that is in the fluid in pan, meat thermo would also be in pan in the same area, they put special tool to check level, it cant leak up, or it would blow out when you remove cap with it running, to use special tool to check level, was all I was thinking
post #9 3) If I wanted to purchase a small scan tool or OBD adapter for my phone to read live data, I would. But, I don’t want to, which is the reason for asking people who know more than me if this is a viable option. totally understand temp difference, but you dont know when the sensor will malfunction, I thought manual said drive/warm up 15 minutes, apply park brake, check in neutral, sensor in valve body that is in the fluid in pan, meat thermo would also be in pan in the same area, they put special tool to check level, it cant leak up, or it would blow out when you remove cap with it running, to use special tool to check level, was all I was thinking
I understand now why you thought I wasn’t willing to spend money, but that’s not what I meant. I just meant I didn’t want to buy those products, but I’d purchase the necessary items to make the gauge idea work.
Also, I see your point about the position of the sensor vs the sensor/temp probe for the thermometer, but the valve body/pressure switch assembly for the 62te is actually mounted on the side of the trans, not the bottom as most transmissions are. This puts it at least 6”-8” above the pan, closer to the center of the transmission, so temps read by the sensor and temps in the oil pan would have a substantial difference. Would it be enough to offset the temp range when checking the level? I can’t say for sure at this point.
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