Can someone verify this? 94 Escort Fan Never Runs

[krugford]

I've got an issue with my 94 Ford Escort 1.9L, as stated in the title, the cooling fan never runs. I've checked over the electrical with a fine tooth comb and cannot find a single fault anywhere. All three relays check good, I have grounds where I should, voltage where I should, and I know the fan works. I can get it to come on by disconnecting the AC pressure switch and putting a jumper on the connector to make it think the AC is running (AC doesn't actually work on this car). It'll make the fan come on low for about 10 seconds, then kick to high and stay there unitl I remove the jumper. The fan just won't run any other time.

Most of my driving is interstate/county road, so it's all 55/65 mph. The only problem is the town I pass through at the halfway point. If I get caught at more than one stoplight, the temp gauge will start to come up. When I get to work or get home and let it sit and idle, the temp gauge will creep up until it overheats (or gets close before I shut it down).

I just noticed a note in the EVTM on the pages dealing with the cooling fan circuits. It says the PCM won't turn the fan on until it reaches 230F. Is this right? That seems awfully warm to me. On the engines I work with on a daily basis, 230F (110C) is pushing the upper limit before a derate.

Am I being overly paranoid here? I've thought about wiring in my own backup switch/jumper to the AC pressure switch to force the fan on when I choose, but I'd rather fix it right (if it needs fixed) or not worry about it. I know there's a few guys around here driving Escorts, whaddya say?

 

[Accord4tehloss!]

Sounds like maybe your coolant temp sensor for the computer is bad ( not the gauge sensor). Or maybe on the escort there is another sensor for just the fans my camaro was like that.

 

[therieldeal]

i dont know too much about the 1.9's but i recall there being like 3 different coolant sensors

join up over at feoa.net, i'm sure someone can help you out

 

[Wicked_Sludge]

mine are an earlier generation than yours is, but being that they are both EEC-IV, the fan setup should be similar...

my cars use an independant coolent sensor for the cooling fan. when it reaches temp, it closes and grounds the fan relay. ive recently added a mechanical temp guage to the blue car and i was surprised to see the fan doesnt kick on until well over 220 (closer to 230). i plan on installing a 200 degree sensor eventually...but for the time being i just wired in a toggle switch.

keep in mind the factory temp guage is not very accurate. its more to tell the driver if the engine is "colder" or "warmer"...rather than the actual tempurature. the factory temp guage on my blue car never went about 1/2 scale before the fan cycled on.

 

[therieldeal]

the temp gauges in the 2nd gens arent TOO bad... i still have the stock gauge in my 95. comparing its movement to the actual temp reading on my megasquirt shows that it responds fairly quickly and is pretty consistant with temp vs. gauge position.

 

[krugford]

Yeah, I know the temp gauge is a relative thing, but I would've thought that it would come on before the needle is sitting just above the "L" in "NORMAL". I don't have good way to actually measure the temperature. I should probably go pick up an aftermarket temp gauge to see what it's actually at. I could be worried about nothing. My paranoia comes from the fact that I've replaced this engine once because it was overheated by the previous owner (probably multiple times) and I fear that I may not have fixed the root cause of the previous engine failure and that it may happen again. Although not likely with as much attention as I pay to the car while driving, it could still happen.

I've checked the temp sensor (for the PCM) while the car is warmed up and the resistance lines up with the graph/table in the PCED manual.

I think my next step is going to involve warming the car up and "replacing" the temp sensor with a 10kohm potentiometer. I'll crank the resistance down until the PCM thinks it's running at 230F or above and see if it kicks the fan on. If it does, then no problem. I guess I've got some more crap to look at.

Thanks for the help so far!

 

[Wicked_Sludge]

the temp sender for the fan is a switch. its either off (infinite resistance to ground), or on (zero, or very little resistance). installing a resister in the sensors wiring isnt going to trick the fan into cycling at a lower tempurature, if thats what your suggesting. the only way to accomplish that is to replace the sensor with one that closes at a lower temp.

if you want to test the sensor, pull it out of the engine and throw it in the toaster for a few minutes. after it reaches 230-ish (im sure wifey has a meat thermometer laying around), hit the terminals with a DVOM.

 

[krugford]

well, i can probe the sensor on the car when it's warmed up, so i know it's working. the temp sensor is a thermistor (on this car anyway). it's resistance decreases as the temperature goes up.

for lack of other options, what i was going to do was a spot check of the PCM's logic. Put a resistor (i'm going to use a pot) in place of the actual sensor and crank the resistance down until the resistance matches what the sensor should be at 230F. If the fan comes on, great, if not, crap.

 

[Wicked_Sludge]

the difference of the fan setup between the newer and older gen cars must be more than i though.

the control setup on my car is silly simple (it doesnt go through the PCM). its just a relay and temp. sensor. when the temp reaches 230ish, the temp. switch closes (not so different than the rangers "dummy" oil pressure guage), grounding the relays coil and sending juice to the fan. to test the relay and wiring, all one has to do is unplug the temp sensor and short the 2 wires.

the reason i said to test the sensor in the toaster is because then you know exactly what tempurature its at. with it still in the car..even if you added a real temp. guage...you dont know if the fans temp sender is actually at 230 or not.