In-car temp sensore

[captinsho]

I am getting no heat in my 93 ATX. I have tested the t-stat, water pump (had to have it out recently) and heater core and all seem to be working. It was recommended I run the EATC test. I did that today and got a code # 3: in-car temp sensor open or short. Could this be why I am getting no heat or is this an additional problem? How do I troubleshoot wether it is a short or if it is open? Where is the sensor and how do I replace it if it is faulty. Any help you guys can give would be great. I am in MI and it was 11 degrees yesterday and 14 degrees today. So basically I am a popsicle by the time I go to/from work. Thanks!

 

[Rob94]

The sensor is located behind the SHO letters on the passenger side dash. I have never had to get to it, but I would assume you could lower the glove compartment and reach your hand up that way.

 

[captinsho]

Could this be why I am not getting heat. I mean I assume so but wasn't sure.

 

[Rob94]

It is possible. Anything is possible with these damn electronic controls. I miss the simply slide/cable style heater controls.

 

[captinsho]

Tell me about it! I miss fricking carburaturs!

 

[rangerj]

Slide cable? Rob you are dating yourself. I have not seen a slide cable in over 20 years! Carburator? A proverbial pain and very inefficient.

Code 03: Tests

1. Sensor open or shorted. Disconnect the wire harness at the sensor ("Temperature sensor assembly"). Measure resistance accross the sensor terminals and compare the sensor resistance to the ranges listed below.
Approximate temperature Acceptable resistance range

50 to 68 degrees F (10 to 20deg. C) 37K to 58K ohms is Acceptable

68 to 88 degrees F (20 to 30deg C) 24K to 37K ohms acceptable

88 to 104 degrees F (30 to 40 deg C) 16K to 24K ohms acceptable

2. Wire harness open or shorted. Disconnect battery cables. Disconnect wire harness connector from the sensor and disconnect both connectors from the control head.

Check for continuity and for possible shorting between the two wires (pin 2 and pin 17 - see wiring diagrams provided in "sticky"). Repair if necessary. Reconnect wire harness and battery cables.

Try the above tests and see what you get. rangerj

 

[captinsho]

I have a parts car so I just swapped the parts and the code is gone. I still have little to no heat. On my 20 minute ride in to work today (16 degrees outside) I finally got a little heat at the end of the trip, but it was not very warm heat. I am puzzled as to what it could be seeing that the T-stat is good, water pump is good, heater core hoses are both warm, one slightly warmer than the other but not by much. I am thinkin that the blender door might not be operating propperly. Any opinions on this?

 

[rangerj]

Check vacuum connections and the blend air door system. Do the control unit self test. If it passes, then you have a mechanical problem (vrs electronic). The blend air door motor would be the first thing I'd check. rangerj

 

[captinsho]

I am sorry to be a pain but you went over my head. Where are ther vacuum connections and how do I test the blend air door system without removing potions of the dash to get back to the blend door. What is the control unit self test? Is this the EATC self test where I push "Off" and "Floor" at the same time and then "Automatic" within two seconds?

 

[NoFlipping]

Is there no heat or no blower? Does the blower work if you turn on the AC?

Cuz, if the fan works (I'm probably wrong, I often am), isn't there a separate temp sensor on the hose running to the heater core that disables the blower until the coolant temp is high enough - to keep cold air from blowin' on ya? Might be reading the coolant as perpetually cold and in turn not blowin' the blower.

Then again, maybe not.

 

[captinsho]

The blower does work but I have not tried the AC. My understanding was that the blower works no matter what but I am definitely not a genius about this stuff.

 

[NoFlipping]

If the blower works, my idea is moot. The AC question was only to bypass the low temp sensor to see if the blower actually operates. Everyone who says blend door is probably right. It was so cold here in detroit last week, that I wouldn't be surprized if the blend door actually froze - my doors ALL froze shut. Good luck.

 

[rangerj]

Captain,

No apology necessary, and you're not being a pain. We are all here to learn and help one another. If you do not understand something you should ask about it. And you have. So here goes!

Yes, I was referring to the EATC self test. I believe that if the blend air door motor is not working the test will bring up a code. My thoughts were to possibly get a hint if the inoperable blend air door code is indicated.

The climate control system uses the blend air door to adjust the temperature in the cabin by allowing outside air to "blend" with the air produced by the heating (or cooling) system. This is how the temperature you select is maintained. If the blend air door is not operating and in an open position (to outside air) your heated air is getting too much cold air "blended" in with it so that you are getting luke warm or cold air in the cabin.

Also in the EATC, or climate control system, there are also vacuum "motors" that operate doors that direct the flow of air being pushed by the blower motor, e.g. the door that redirects the air from the front of the dash to the defrost vents when you push the defrost button. So, I suggested that you check the vacuum lines and vacuum motors for any that are not operating correctly.

There is a vacuum control unit in the EATC control that gets its vacuum from the engine via a line (black) that goes through the firewall at about the center of the firewall. The line iis attached to an in-line check valve near a vacuum resevoir. (black canister).

The control unit directs the vacuum to the 3 (I think) vacuum motors, 1. to the right the one that controls the outside recirculation door (white line), 2. the one in the middle that controls the right and left indtrument panel registers ( red and blue), and 3. the one that controls the defrost door (yellow).

So, if these doors all opeate properly when you "push their buttons", which would indicate that the vacuum system is OK, then we are back to the blend air door and its motor. Operate the button and listen for the doors to operate. If you do not have a vacuum pump you will have to have the engine running to get vacuum (manifold vacuum).

I may be easier to remove the glove box and a work light or flash light and visually watch the doors operate.
Keep in mind that you may not have to do any of this if the air is being directed properly, e.g. if you put on defrost and the air is directed to "defrost" then that vacuum motor is working properly. If the other doors operate properly when the botton is pushed then the vacuum system is OK.

Do some or all of what is recommended above so you know better what is or is not working properly in the EATC system. Then get back to us and we can narrow the problem down. Just for grins and giggles, if you have a parts car pull the blend air door motor and try it on the car in question! rangerj