well I am getting frustrated buy this but any ways the original water temp sensor lasted 16 years and now all of a sudden they keep going out? this would be my 3rd temp sensor in 1 month this is the sensor on the water pump housing. and when this sensor go's out the car is extremely hard to start. I know its that sensor because the cooling fans won't turn on on unless I jump the harness with a paper clip. so any suggestions on what is going on or how to fix it?

 

Look guys I took my car to a good friend who has helped me in the past on car electrical stuff. but this time we are both stuck on this.

stuff replaced
1. new relay
2. new water temp sensor
3. checked all grounds
4. checked all fan connections

and the only way they turn on is if the water temp sensor is unplugged or if the harness is jumped.

also on data master it shows that temp sensor is in fact working and I get no engine light when its plugged in so Any input would be much appreciated.

 

This scenario does not sound right. You say Datamaster shows the temp correctly, but you say the sensor is bad? It would be a bizarre situation that would cause repeated sensor failures. When you "jump the harness", do you mean at the DLC? Are you monitoring the scanner temp until it show it reaches or exceeds the ON temp of 226°? Unplugging the temp sensor causes a trouble code (that turns on the fans, as most trouble codes do). That does not mean the temp sensor is bad.

 

What exactly happens to the sensor when it is "go's (sic) out" or is "blowing"? When it has failed, what is the resistance across the two pins? Is it indicating an open circuit, or a shorted circuit? That's about the only two things that could happen to make it fail. Or is it a mechanical failure involving cracking?

 

The harness was the conector for the water temp sensor and yes datamaster shows the temp correctly and I have all the old water temp sensors and they all checked out within specs. so I noticed this problem only ocorse with the water temp sensor plugged in. and yes the water temp climed right on buy 226* thats when i got concerned. So is their a way I can bypass the whole circuit and rewire the fans so when ever the key is turned on the fans just run 100% of the time? or is their a manual switch on tuner cats that I can just activate them like that?

 

So what you are saying is there is no code for your CLT sensor, they are not failing, and they are indicating the correct coolant temperature, but in your mind they need to be replaced because they are "going out" and "blowing". Doesn't make any sense at all.

You can wire your fans to a manual switch.

Courtesy of Shoebox:

http://shbox.com/1/fan_sw_diagram1.jpg

Or you could do a bit more diagnostic work to find out why the fans are not turning on at 226*F.

 

you need a wiring diagram and a power probe because there is no way you got 3 bad coolant temp sensors.

 

If you jumped the connector to the sensor (which I don't recommend you do), it would indicate a very high temperature to the PCM. That should cause the fans to come on (and they did, according to you). That would indicate there is nothing wrong with your fan circuitry.

So, you actually monitored the engine temp with a scanner until it was 226° and you did not see an ON command (via the scanner) for the fans (and fans did not come on)? Sometimes you may have to wait for the temp to increase a few more degrees before you see the ON command. If you did see the ON commmand and the fans did not turn on, did you check the dark green fan relay control wire for presence of a ground coming from the PCM? That is what turns the low speed fans on.

Has the PCM ever had any programming alterations?

http://shbox.com/1/fan_schematic_1995.jpg

 

There is a separate sensor on the head that provides information to the instrument cluster. That sensor may be bad, providing the wrong information.

 

so yes their is no cel light and yes I would agree their isin't any way the circuity is bad so last night I let the car just idle and monitored the water temp with data master and the fans cam on at a temp of 261* and I could confirm that because i shot the bottom of the radiator with my laser thermometer and it said 259* and their was still no cel light dose 261* not qualify as a over heating to the ecu?

 

261 is a bit high (I would not be letting it get that high). Fans are supposed to come on at 226. I'd try another PCM (or check the programming with a tuner program).

 

I will check the programming, and i think im going to just wire it so the fans are on 100% of the time.

 

I never recommend doing that. It is a waste to have them on all the time and can inhibit it from reaching operating temp when ambient temps are low. Wear on the fans and constant load on the electrical system (fans take a lot of power to run) are two more reasons not to do it. Just an overall bad idea. MHO, of course.

 

You don't get a check engine (SES) light for high coolant temp. You just get the "check gauges" light on the dash. You get an SES light and a code if the sensor is putting out irrational temperatures (-56*F or below, 284*F or above).

 

Really I thought because whenever I unplugged the water temp sensor data master showed 305* so I assumed the ecu assumed it was that high and just turned the fans on.