Engine Temp Sensor Removal ?'s

ecs · Post by **ecs** » Tue Jun 19, 2007 11:34 pm

Alright, so i went to the yard today to grab another engine temp sensor since my temp gauge doesn't work. However when I tried to take it out I notice that I can only get to it with the open end of my wrench. The closed end won't fit over the connector unless I cut it off and I can't get a socket over it because of the wires.

Also, when i tried to get at it after cutting the connector off I didn't have enough room for the wrench to "catch". And no matter where I try to turn I either hit the throttle body, fuel lines, cylinder head, there's ALWAYS something preventing me from getting enough turn to catch the wrench on the hex part.

Do I just have fat hands or does anyone else have this problem? And the sensor i'm talking about is on the rear passenger head (ETS), not the one in the lower intake manifold (CTS).

ecs · Post by **ecs** » Thu Jun 21, 2007 2:27 pm

Nevermind, got it out and replaced it with a junkyard one. Still reads nothing on the cluster. Sigh.... at least i found a full gauge (oil, batt, and tach) at the junkers and it works perfectly just had to swap my mileage over to it.

Guess i'm going to have to get a voltmeter and measure the readings. Does anyone know what I should be looking for? Resistance (ohms), voltage, etc? I'm thinking resistance but i'm not quite sure. Also does anyone know the reading that I should be getting from the sensor outside of the "cold" range?

Oh and for anyone who is following this thread, I think the sending unit used a standard size wrench. I had to wiggle the 14mm on there to break it loose. The 15mm wrench was only rounding the hex head off the unit. Damn, getting these sender units off are a *****, but a hell of a lot better than paying 60 bucks for a new one.

rweatherford · Post by **rweatherford** » Sat Jun 23, 2007 10:35 am

Someone with a factory service manual can give you the values for that sensor.

ecs · Post by **ecs** » Sat Jun 23, 2007 11:57 am

I don't think I need them now... I replaced the sensor with another one from the junkers and it seems not to be working... Might as well start tracing the wiring already. I was hoping it wasn't the wiring.

Post by **Cliff8928** » Tue Jun 26, 2007 2:48 am

Which sensor did you replace and what year is your car?

ecs · Post by **ecs** » Tue Jun 26, 2007 10:06 am

I swapped out the engine temp sensor (the one in the rear head) and the temp gauge was still not moving at all. I'm thinking about stripping some insulation past the connector on both ends and try jumping it like that. Maybe the connectors are bad... or at least that's what i'm hoping.

My car is a 93 with the 3.1

Post by **Cliff8928** » Tue Jun 26, 2007 12:50 pm

Is that the style that has two wires on it? You should be able to connect them together and get the gauge to peg the "H" to rule out the chance of a faulty cluster. Or if it's a one-wire sensor you should be able to just ground it.

quad4gtz · Post by **quad4gtz** » Tue Jun 26, 2007 7:09 pm

DO NOT jump power to this circuit. Doing so will most likely blow the circuit in the ECM. As cliff8928 describes giving the circuit ground should make the gauge go to full hot(low resistance). If you happen to have a fuel gauge sender lying around, connect it to ground and the ECT circuit. You should be able to slowly sweep the gauge up and down.

ecs · Post by **ecs** » Tue Jun 26, 2007 11:41 pm

I wouldn't jump power to it.... What I said I was going to do was bypass the connectors on both ends to rule out bad connectors.

Ah, i'll try connecting both ends together and see what that does. I have the 2 wire connector. I haven't seen any 3.1 L bodies with a 1 wire sender. All the J bodies i've seen that have the 2.8 or 3.1 seem to have the 1 wire sender.

I really doubt it's a bad cluster because i've been through 3 clusters. I replaced the first one because of a sticky fuel gauge and I thought it might cure the temp problem but it didn't. The second time I replaced it was with a full gauge cluster and the temp gauge still doesn't work.

ecs · Post by **ecs** » Wed Jun 27, 2007 12:06 pm

Connecting both ends of the harness connector together just made the needle sweep and come back to C. Note that with the connector from the sender plugged into the harness it wouldn't sweep or do anything.

However, with the harness connector grounded I was able to make it go all the way to H and put the coolant light on. So I guess that rules out the harness connector and the wiring... but wait...

I decide to plug in a sender to the harness without it being in the cylinder head. Same thing happens when I have it plugged into the one inside of the cylinder head which is... nothing. So I end up peeling back the insulator on the sender wiring and grounding that while the sender is connected to the harness. I can get it to go to H and the coolant light to go on so obviously both connectors (sender and harness) are fine and the wiring is good.

So I get the bright idea that maybe there is an air pocket in the cooling system not letting the sender get a decent reading. So I boil a pot of hot water and sit the sending unit in it... nope nothing happens. So I try the other sending unit I have..... nope nothing there either.

It's just so hard to believe that ALL THREE sending units are bad... Does anyone else have anything to add here? I'm stumped, outside of buying a new sending unit (I want to make sure the sending unit is the problem).

Post by **Cliff8928** » Thu Jun 28, 2007 12:37 am

It is possible that the sensor signal wire is good in the harness, but the sensor ground wire is not.

ecs · Post by **ecs** » Thu Jun 28, 2007 9:29 am

Does the sensor have a ground wire? There is a blue (coolant light) and a blue/white (gauge reading) and that's it.

Post by **Cliff8928** » Thu Jun 28, 2007 12:22 pm

I guess not then. I was thinking of the way a different sensor worked then....

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