I have a 94 Dakota 3.9 with a bad temp sensor and have been having huge trouble finding one that will fit. Our Dodge dealer said they were discontinued two years ago. I have tried three from parts stores and three from a junkyard. They're all just a little too big to go in the hole. The old sensor is a one wire type and I'm wondering if it may be a metric size. I have read that most sensors are 1/8 27 pipe thread and that is what all I have been able to obtain were, but as stated, they were all a few thousandths over sized. Does anyone know where I can find one that will fit?

 

The one wire is for the gauge.

Did you want to replace that, or the ECT sensor for the ECU, which is a 2 wire sensor?

RwP

 

Assuming you have the correct sensor try cleaning the threads in the intake manifold. use a round wire brush or a tap.You might just have old thread sealer hardened on there. Or you could find out the size of the threaded hole and run the sensor through a threader of that size.

 

Ralph, my engine has only one coolant temperature sensor and it has only one wire. There is another temperature sensor nearby but it is a Manifold Air Temperature sensor. Some people may assume it is for coolant temperature.

 

One More, I have thought about trying to re-thread the hole, even bought a 1/8 27 pipe tap, but because it is in such an awkward place am a bit afraid I might get it out of alignment then have two sets of threads in the hole. I may go ahead and try it since I don't know what else to do without paying a pro a couple hundred or so, which I can't afford.

 

No.

If it's a 3.9, it's got TWO coolant sending units.

Check your wiring; check the factory service manual.

And no, I am NOT assuming anything.

I do not have a 1994 FSM handy; otherwise, I'd just drop that off here; but I DO have 1995 and 1996 both (see the FAQs); for a 1995, page 8W-40-8 shows the gauge sending unit, but page 8W-30-25 shows the ECU's unit, which it describes as front center of intake. It ALSO shows the IAT sensor on page 8W-30-25, which is a different sensor.

Attached are both pages.

RwP

 

I have a 94 3.9 and there are two temp sensors right next to the thermostat housing. They may be on opposite sides of the housing I do not recall exactly where they are.
When you chase threads to clean them you do your best to get it started straight then turn only 1/4 turn and back it out then turn it in by hand and it should go easy to the place you stopped and go 1/4 turn and back out again. Look for debris and clear it away when you pull it out. And so on.You should not be cutting new thread if its just gunked up. If you want to enlarge the hole you can cut new thread but you would have to go with a bushing to mount the temp sensor to it.To do that get the bushing that has a hole that fits your sensor then drill a bigger hole in the old one and tap it.

 

I believe the sensors are pipe thread, so, tapered. Standard tap won't work.

 

Plenty of both sensors available on RA. I replaced both of my recently, both sensors were crapped out. No fitment issues either. The grey sensor is 1 wire the black is 2 wire.

94 Dakota

Steve

 

Ralph, I owe you an apology. This morning I looked where you said it should be and found the second sensor. It's really hard to see and I would have looked right at it not realized what it was if I didn't know it was supposed to be there. That is not the one I am concerned about however. I didn't make it very clear that my gauge isn't working and that is what I'm trying to fix. I might even be able to get the right one from a parts store now that I know to tell them there are two and I need the gauge sender. I have to wait until my next SS check comes to try that.