Coolant Temperature Sensor
 

1994 Honda Accord LX (4cyl, nonVTec)

I am looking for some Barney Style assistance here as I am working out of a Hayne's manual with piss poor schematics and pictures from a dozen different vehicles.

First of all the passenger side fan; is this a radiator fan or is this the condenser fan. I'm not sure what they are trying to call it but simple logic tells me it's mounted on and blowing on the radiator so it is a radiator fan.... as is the fan on the driver's side.

At any rate, this thing turns on whenever I turn the key in the ignition. When I am finished drving and turn the car off (nomatter how long or short the drive was or nomatter how hot or cold the ambient temperature is) the fan will stay on for four to five minutes.

Obviously the problem lies within a bad sensor and/or switch but which one(s) are the culprit(s). With everything snugged into harnesses and packed into the engine compartment like sardines it is hard to start manually tracing wires and find eveything that connects to this fan and like I said, the schematics I'm working with here suck.

I have checked the sensor in the thermostat housing which shows zero resistance with the engine off and cold. Could this likely be my only problem or is there something else I should check?

Re: Coolant Temperature Sensor (motorbreath777)
 

I'm guessing here because I'm not that familiar with your flavor Honda. (Nice detail in the post BTW)

As far as I know, the TW sensor never reads zero. The lowest is about 200 ohms. I would expect starting problems if that was the case since it tells the ECU how cold/warm the engine is. If you read it correctly, that could be your problem though. There are is/are sensors mounted in the bottom part of the radiator that will trigger the fan(s) too. They basically 'close' and complete the circuit to ground when they reach a certain temperature. Look for and check those too. The condensor fan should only come on when the AC is active, AFAIK.

Re: Coolant Temperature Sensor (Perfectionist)
 

failure of this sensor will not cause the car not to start. failure of the temp sensor will cause problems with the ecu thinking that the engine is either at operating temp or not. The other temp sensor is used to trigger the cooling fan when the car is running and the temp reaches a certain point.

When you start the car it uses a default parameter set to get the engine running. Once the engine is running it will then start taking readings from various sensors.

The passenger fan is for the A/C i believe.


It sounds l ike your temp sensor for the fan is telling the ecu that the car is too hot because it has failed. once you test and verify, you can replace it and the problem should go away.

Re: Coolant Temperature Sensor (YeuEmMaiMai)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by YeuEmMaiMai &raquo;</TD></TR><TR><TD CLASS="quote">When you start the car it uses a default parameter set to get the engine running. Once the engine is running it will then start taking readings from various sensors.

.</TD></TR></TABLE>

That's basically true. However, a failed TW sensor has been to blame for the 'hot soak restart' problems that creep up more often than not. The ECU trims the injector pulse based in part on the engine temperature. A faulty TW sensor would trick the ECU into trimming the pulse for a cold engine. If the engine is already at operating temperature, flooding can be the result, and no start.

Re: Coolant Temperature Sensor (motorbreath777)
 

the next time you shut off the car and the fan is still running; unplug the sensor that is in line with the top radiator hose. If the fan quits you have found the problem.
I'd like to figure out how the original post got TWISTED into a starting condition post LMAO

Re: Coolant Temperature Sensor (hondadude)
 

Yes I believe its the sensor on top of the upper radiator hose. I have a similar problem. I hope somone can help too. My wife have a 94 ex sedan with over 240k miles with no rebuild. But only oil changes. Recently the car has been overheating no matter what condition just like yours. But no coolant loss. Even in the morning when I start the car it'll just rise all the way to the top above H (hot) but the fan wont turn on like it suppose too. So I replace I mean switch the fan swith sensor and temp guage sensor to my car which is a 92 civic si. But with the accord sensors in mine it works fine. and the civic sensor to the accord does the same. My question is "what the f*** is going on here? Can anyone help?

Re: Coolant Temperature Sensor (motorbreath777)
 

well atleast you gave a very detailed post lol not like other "my fans just keep running and wont turn off" atleast you have a pretty good idea of what the problem could be. Simply to make life easier i would run down to the auto parts store and buy the following....

Condenser Fan Switch which is located on the upper radiator hose
ETC Switch sensor which is located ontop of the thermostate housing
coolant temp sensor for the ECM which is located under the distributor cap.

i have a 1994 honda LX 2.2 5 spd and i had the same problem and it turns out to be that the ETC Switch Sensor was bad all this information is on page 3-4 3-5 of the haynes manual

back to the list i would go out and buy those items and replace each one to see which one would solve the problem and try each one at a time. and make sure the car is running to operating temp. and then return which ones you dont need or since pepboys likes to dick people for prices i had just returned the old ones and kept all the new ones.

it is normal however that honda will tend to keep the fans running for like about 2 min after the engine has been shut off to cool it down once the engine has been turned off. but i guess only if its mad hot out or you were driving the car fast and the engine got hot fast.

Re: Coolant Temperature Sensor (vampire7608867)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vampire7608867 &raquo;</TD></TR><TR><TD CLASS="quote">Yes I believe its the sensor on top of the upper radiator hose. I have a similar problem. I hope somone can help too. My wife have a 94 ex sedan with over 240k miles with no rebuild. But only oil changes. Recently the car has been overheating no matter what condition just like yours. But no coolant loss. Even in the morning when I start the car it'll just rise all the way to the top above H (hot) but the fan wont turn on like it suppose too. So I replace I mean switch the fan swith sensor and temp guage sensor to my car which is a 92 civic si. But with the accord sensors in mine it works fine. and the civic sensor to the accord does the same. My question is "what the f*** is going on here? Can anyone help?</TD></TR></TABLE>

have you checked the t-stat make sure it is opening ???

Re: Coolant Temperature Sensor (motorbreath777)
 

If I were to replace my ect , would I have to drain the cooling system ?

Re: Coolant Temperature Sensor (motorbreath777)
 

If you are referring to the actual engine coolant temperature sensor located under the distributor. Then yes, you will have to drain it. At least to a level below the cylinder head. Now if you are talking about replacing one of the two temperature switches, A or B. Then you may not have to drain very much, if any. Where they are at a level that is relatively high in the system.

Don't forget to bleed the system fully after you do this.

Re: Coolant Temperature Sensor
 

Okay thank you! And how would I bleed it ? And what what's if I don't ?

Re: Coolant Temperature Sensor
 

What happens if I don't ?

Re: Coolant Temperature Sensor
 

Turn heater temperature dial in the car to full red. Jack the front of your car up....open the bleeder bolt at the thermostat housing(it's a 12mm head bolt)...fill the radiator up until it starts coming out of the bleeder bolt. Close bleeder bolt. Fill up radiator til it's full. Put cap on. Start car and check for leaks.

Re: Coolant Temperature Sensor
 

are you sure anything is even wrong? some cars have fan timers that keep the fan running after the key is off, I know the earlier Accords do

Re: Coolant Temperature Sensor
 

It's not about the fans but I hear the ect , helps the ecu with ignition and helps withe the fuel mixture . And gives Hondas some starting problems in rare cases .

Re: Coolant Temperature Sensor
 

lostforawhile, You have to realize that this is a 7 year old thread that has been bumped by Mikzize with a different question than what was originally posted. ;)

His question actually has to do with the engine coolant temp sensor, not the A & B temp switches.


Mikzize,
Yes the ECT does effect the ignition, if it is dirty or malfunctioning it can cause driveability issues.
What seems to be your problem would be the better question to ask here.

If you want you can test the ECT fairly easy if you have a multimeter. If your car will start and idle you can try testing the ECT this way.

• Start car and let it idle until the fans come on, this indicates that your engine is up to operating temperature.
• Disconnect the 2 pin connector from the ECT located under the distributor.
• Measure the resistance between the two pins on the ECT sensor
• You should see between 200 - 400 Ohms. If not you should replace the ECT sensor.

Re: Coolant Temperature Sensor
 

Yes ! Right on ghost accord and thanks holmesnmanny , I thought my way of bleeding the cooling system was different from yours . I have never open the bleeding valve I wait for the vehicle to do it for and push all the air bubbles out into the over flow , with the heater on high of course

Re: Coolant Temperature Sensor
 

Hey crew,
You guys got me confused, i have an 1995 accord with the 4cyl motor. im having temp issues. what are the 3 sensors you guys are mentioning the one on the top of the upper radiator hose the lower hose at the t-stat housing and this one under the distributor cap. i replaced the coolant sender under the distributor cap. but no change. i dont need to go into detail because there's alot of similar issues from others. Im just curious what sensors are. thank you