Temperature Gauge Erratic

[Griffon]

1997 Contour GL Zetec Engine.

The other day I was driving to a friends house when I noticed my temperature gauge was burried all the way to the right in the red hot zone. I immediately turned the hot air on full blast. As soon as I did this the temperature gauge quickly dropped to the middle in between the letters "M-A" I kept the air on and drove to my destination. When I was driving back everything was normal.

Today on the way back from a meeting I noticed the needle pegged to the red zone again. I was on the expressway only a couple miles from my home. I quickly turned on the hot air and the needle stayed buried. I pulled off the road, waited for about 20 25 minutes and then started to head home. The car needle never moved since.

I thought it was my fans because I don't notice them turning on at all. Even when I turn on the cold air or hot. I read through several posts to diagnose this problem. Here's what I did. I jumped both the lowspeed and highspeed fan relays, both worked perfectly. I tested the actual relays with a 9 volt battery (both clicked as it should)

I was confused so I moved on to testing the temperature gauge sender. It was really difficult to access (because of all the hoses) but I noticed that the actual plastic around the plug is cracked. I'm assuming this is part of my problem. I do know that the actual sensor is fine becuase I just replaced it about 2 months ago.

Any suggestions for me? The needle stays burried right, even when I unplugged that sensor. (Maybe I didn't do something right) I'm really confused as to what's happening here.

 

[alex894]

get a reader and see what the actual temperature is; My temp gauge has been dead for a year and temperature is just fine.

Short the gauge and see if the gauge goes back to cold before you plug it back on the sensor. Also, when you unplug the gauge plug, your high speed fan SHOULD kick in

 

[Griffon]

How do you mean short the gauge?
Get an obd II scanner? or what type of reader would I need to see the actual temperature?
When I unplug the temperature sender sensor plug, the high speed fans should turn on? Is this with the car in the on position or is this with it started?

 

[alex894]

1. unplug the temp gauge wire from the sending unit and short it with a jumper(can be a "u" shaped wire). unplug and short with the key turned in the "on" position, motor not running. The needle should go on the highest point at HOT and then drop dead once you remove the jumper from the plug.

2. yes OBD II scanner is the tool. Any reader that gives you live diagnostics will do.

3. when you unplug the gauge, the high speed fan kicks in ONLY WHEN THE engine is running/car is started.

Let me know what the results are.

 

[Griffon]

I unplugged the sensor, shorted it with a u shaped wire and noticed the gauge started to go down very slowly. I went back to do it again and it went back to high. Then I did it again and it came back down. I noticed that coolant saturated this plug inside and out. There must be a leaky hose end or something because it is wet. I turned the car on with the sensor unplugged and no fan came on. I have a feeling that the plug end is toast.

 

[AliasJerk]

the pre98 zetec contour had an issue where the coolant temperature sensor was overly sensitive, and in some cases would not turn on radiator fans when it should.

Advance Auto parts has the part for $18, and it is located on the top of the thermostat housing directly to the left of the Air intake box (where the air filter resides).

 

[alex894]

weird, weird....

if coolant was in/all over the plug that would've shorted the gauge, which in turn would cause an alarm and the fans would be spinning like crazy.

Run the car for a minute and while running unplug the gauge; NOT unplug and then start your car, run and unplug, I'm curious.

If a newer plug is the solution, tape that sob with electrical tape or shrink wrap.

 

[Griffon]

I am going to do this tomorrow... I am at work all day. I have a question though, Aliasjerk... what are you talking about?? What do I need to buy? Is it a new wiring harness?

 

[Griffon]

bringing an unsolved mystery back from the dead. I wanted to show you guys something. My gauge has been to the cool position ever since. It doesn't budge. Fans never turn on. I can not turn the car on and then remove that plug (too hot and hard to get to with engine running.) So I unplugged it today and noticed something... It came off in my hand! Was wondering if I could just buy a whole new plug. Let me know where I can find the part if it's possible. I really think that's the problem Wink.

 

[Griffon]

any news on the part guys?! Ehh, I've been going to part store after part store and no one can help me out. I looked through the motor craft website and found a plug that looks exactly like it. The thing is though, when I look up the part number on rock auto the page says it's a cam sensor. Does it really matter? It looks the same.

Here are the ones that I was looking at. One of these has to be it!

 

[iskoos]

Well correct me if I am wrong guys but I read somewhere over here that the sensor on top of the t-stat housing is the one used by PCM. The sensor that runs the gause is actually under the t-stat housing.

Shouldn't Griffon replace the one under the t-stat housing?

 

[Griffon]

I did replace that sensor. The one below the t-stat housing. Coolant leaked all over that plug end and corroded the wire/plug end. It actually came off in my hand while I was unplugging it. I went to the junk yard and clipped of that plug and will be putting it on tonight. I will let you know if my issues are resolved. *Crosses fingers*

 

[Griffon]

Yay! The gauge now works correctly. I got the new plug on and noticed the gauge works. I took care of the coolant leak too. Problem is, the fan's still don't seem to be coming on. I know they work because I jumped the relays, but is there another wire that controls the fans? I'm confused as to how the sending unit to the gauge cluster will trip the fans on? Is there something else I should check?

 

[Lord Stanley]

Problem is, the fan's still don't seem to be coming on. I know they work because I jumped the relays, but is there another wire that controls the fans? I'm confused as to how the sending unit to the gauge cluster will trip the fans on? Is there something else I should check?

The sending unit on top of the thermostat housing is what turns the fans on; it is the unit which sends a signal to the PCM... If you unplug this sensor while the car is running, you should notice that the fans will run all of the time... How hot did you let your car get? The low speed fan on a Zetec does not come on until the L or a little after L in "NORMAL"...

 

[Griffon]

well that's lame! I never let it go past the L in normal. It never gets to the red. It's always within the normal brackets. Is there a fix for that? I changed that sending unit below the thermostat out with an autozone part, guess I should have gotten it somewhere else. I hate how it goes all the way up there, I would expect it to sit somewhere in the middle.