TCCoA Forums banner

1 - 20 of 35 Posts

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #1
Hey Guys, Ive noticed lately that my fan doesnt turn on until the temp gauge gets to the upper range, it does it mostly in slow speed driving, on the highway it never goes beyond midway, and when the A/C is on it never goes past midway, could this be the CTS or the Relay?, by the way its a 1997 4.6, thanks
 

·
Super Moderator
Joined
·
9,312 Posts
There are a couple things worth noting before we start suggesting possible problems.

The 97 coolant temperature gauges have a lot of variance from the factory. A particular temperature on one gauge may register 1/2 and 2/3 on another gauge. It's not a reliable way to determine temperature of the engine except in a relative sense (comparing the same car to itself).

Do you have access to a scan tool or other device which can tell you the coolant temperatures as it's being read by the PCM? That will tell you if the car is actually behaving as it should be or if there is a possible problem. The computer in a stock program turns on the low speed fan once the coolant reaches 210 degrees then off again at 200. If the coolant reaches 220 degrees the high speed fan turns on, then when the coolant drops below 210 it reverts to low speed.

Also - with the a/c on, the fan is running 100% of the time the pressure in the A/C high pressure lines is above certain point while the vehicle is moving under 48 MPH. Because of this constant airflow over the condenser and radiator, your coolant temperatures are more likely to remain closer to the 195 degrees at which the thermostat opens than in city driving with A/C off, translating to a lower gauge reading while moving down the highway or with A/C on.
 

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #4
There are a couple things worth noting before we start suggesting possible problems.

The 97 coolant temperature gauges have a lot of variance from the factory. A particular temperature on one gauge may register 1/2 and 2/3 on another gauge. It's not a reliable way to determine temperature of the engine except in a relative sense (comparing the same car to itself).

Do you have access to a scan tool or other device which can tell you the coolant temperatures as it's being read by the PCM? That will tell you if the car is actually behaving as it should be or if there is a possible problem. The computer in a stock program turns on the low speed fan once the coolant reaches 210 degrees then off again at 200. If the coolant reaches 220 degrees the high speed fan turns on, then when the coolant drops below 210 it reverts to low speed.

Also - with the a/c on, the fan is running 100% of the time the pressure in the A/C high pressure lines is above certain point while the vehicle is moving under 48 MPH. Because of this constant airflow over the condenser and radiator, your coolant temperatures are more likely to remain closer to the 195 degrees at which the thermostat opens, translating to a lower gauge reading.
No I dont have a scan tool, but the gauge gets to 3/4 mark and the fan always come on, how about using a infared temp checker on the radiator?
 

·
Super Moderator
Joined
·
9,312 Posts
Point it at the coolant crossover on the intake since that's where the temperature sensors are. If it's within a few degrees of 210 when the fan comes on you don't have anything to worry about. :)
 

·
Super Moderator
Joined
·
4,941 Posts
I'll add that if you have an Android phone or tablet with Bluetooth (all phones, probably about any tablet over $200 or so), you can pick up some Bluetooth OBDII pods for under $100 - well worth it, but be sure you can return it in case it can't read the Ford data stream (some of the cheapies are hit and miss on that.)

If you have an iDevice, they also make WiFi versions of the dongles.

I'll state that it's almost sinful to NOT have one, what with all the info the computer can give you. It's even better if said combo with the software on the iDevice or Android device can datalog (like the $5 Torque for Androids can ... )

RwP
 

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #8
I'll add that if you have an Android phone or tablet with Bluetooth (all phones, probably about any tablet over $200 or so), you can pick up some Bluetooth OBDII pods for under $100 - well worth it, but be sure you can return it in case it can't read the Ford data stream (some of the cheapies are hit and miss on that.)

If you have an iDevice, they also make WiFi versions of the dongles.

I'll state that it's almost sinful to NOT have one, what with all the info the computer can give you. It's even better if said combo with the software on the iDevice or Android device can datalog (like the $5 Torque for Androids can ... )

RwP
Sorry ralph, but Im a low tech man in a high tech world, are you saying i can get a something for my Andriod phone that acts as a scan tool and where can I get one ,Thanks
 

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #9
Sorry ralph, but Im a low tech man in a high tech world, are you saying i can get a something for my Andriod phone that acts as a scan tool and where can I get one ,Thanks
Hey Ralph, I went online and found what your talking about, I also checked Harbor freight and they have a scan tool for $80 that looks like it does what I need and is updatable
 

·
Registered
Joined
·
12 Posts
I have been having the same issue with my 1996 4.6 as well. The temp guage gets to just slightly over the half way mark before the fan comes on. I have replaced the t-stat and the switch on the coolant crossover nearedest the thermostat. The Ford dealership wasn't able to tell me what the switch on the opposite side of the coolant crossover pipe was. Maybe it was the individual at the counter. So that switch is also for fan control as well?
 

·
Super Moderator
Joined
·
9,312 Posts
The sensor with the green plug is for the gauge, the other is for the PCM. The gauge sensor has nothing to do with when the fan comes on and is only used by the gauge on the dash. The PCM reads the ECT through the sensor on the crossover with the gray plug, then commands the fan to come on as needed.
 

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #12
The sensor with the green plug is for the gauge, the other is for the PCM. The gauge sensor has nothing to do with when the fan comes on and is only used by the gauge on the dash. The PCM reads the ECT through the sensor on the crossover with the gray plug, then commands the fan to come on as needed.
So would replacing the CTS fix the fans low speed setting? The low speed comes on when A/C is on, I guess I need to verify what temp is when the fan comes on, Thanks for the help
 

·
Super Moderator
Joined
·
9,312 Posts
How do you know the fan's low speed setting needs to be fixed? The fan's operation which you described earlier sounds perfectly normal.

If you're convinced it isn't, then be sure to get a reading on the actual coolant temperatures before you start replacing parts. No sense in replacing parts that aren't failing.
 

·
Registered
Joined
·
12 Posts
So then the green plug is the one that my Ford dealer couldn't identify. Now I know. Thanks! Is it possible then that my sensor for the guage itself could be dirty or off in some way?

Additionally: are all the electric cooling fans on the 4.6 two speed? If so then how do I test that both speeds are working properly?
 

·
Super Moderator
Joined
·
9,312 Posts
Don't rely too heavily on the gauge on the dash. Like I said in a previous post in this thread, the factory gauges aren't very accurate. Case in point: My 94 3.8 used to read just barely left of "N" when cruising. Then it started to show cooler and cooler. I went through two thermostats and a temperature sensor, nothing changed it. Until one day I had the gauge cluster out and 'flicked' the temperature needle from one end to the other, then it went back to normal. The gauge was reading incorrectly, my temps were normal all the time.

Yes, all the electric fans used on MN12s are two speed. Unplug the gray connector and the high speed fan will come on. A/C uses low speed IIRC.
 

·
WOT Junkie and avid corn burner
Joined
·
3,734 Posts

·
Lightly Seasoned
Joined
·
717 Posts
Discussion Starter #17

·
Premium Member
Joined
·
5,862 Posts
I bought my Actron CP9035 in 1996 and I still use it today - works great! lol

I like Ralph's idea about the bluetooth scanner for my Android - that's pretty kewl and I'll have to get one!

 

·
Registered
Joined
·
12 Posts
Perfect then. I'm not going to worry about. I had it hooked up to the OBD tool 2 weeks ago and it showed no fault codes. The car isnt a leaker and hoses are good so I'm just going to chalk it up as this is it's normal state.

Thanks for all the good information. Glad to know what the green top plug is finally!!
 
1 - 20 of 35 Posts
Top