'94 SC A/C and Temp Gauge Issues

tedallen

Registered User
The A/C on the subject vehicle is behaving abnormally while accelerating (not WOT) and with the climate control in Max A/C setting. Under these conditions, air flow is diverted from the panel vents to the defrost vents until I back off the throttle somewhat. When the air is on, it is cold, and in Normal A/C mode, it does not divert to the defrost vents under acceleration.

I have read numerous other posts regarding A/C, cooling fans, etc. I also found one regarding a red plastic vacuum tube near the firewall on the driver's side that might be related to this behavior. I found what I believe to be the correct vacuum line and see it going into a vacuum tree behind the intake manifold, but cannot see where it goes to. Any ideas?

Also, although my cooling system is full and my radiator less than 2 yrs old, I quite often see the temp gauge surge up near or past the "L" in normal, most notably when sitting idling at a drive thru window or excessively long traffic light and will frequently jump/surge. I jumpered the wire going to the coolant sending unit directly to ground and the gauge goes all the way to hot and remains steady once the ignition switch is turned on. I'm not certain if either of the fans are running when they should, however, when performing a KOEO test, I confirmed that the "puller" fan runs in both speeds and the "pusher" fan comes on as well.

What sensors are used to determine when these fans come on? The wiring schematic I have shows the cooling fans connected to the Constant Control Relay Module which in turn has connections back to the Powertrain Control Module which also has connections to the A/C controls system. Should I check/replace the coolant temp sensor (goes to computer), coolant temp sending unit (goes to gauge, not sure if goes through another control module first), or some other sensor(s) and or relay(s)?

Based on the gauge behavior, I am tempted to change the coolant temp sending unit, wondering about the coolant temp sensor as well.

Any and all ideas are greatly appreciated!
 
I believe that the tube that you are referring to runs along the firewall to the passenger side.Then goes thru a access hole to the inside of the car.:)
 
My 94 runs hotter when the AC is on. Sometimes the climate controls act strange, i've never figured it out, but im just glad it blows cold.

g'luck fixin your problem

-Nick
 
No idea on that AC problem, very very strange. I can offer advice on your cooling problem though. First, how long has it been since you flushed your cooling system and replaced your coolant? If it's been more than a year or two, I recommend you get that done. You won't believe what comes out of radiators...

Next, consider replacing your thermostat. It is a cheap and easy job to do yourself, and can fix this. If neither of those work, consider getting an auxiliary fan. I have a 14" fan mounted in front of my radiator that goes to a toggle switch under my dash. If I'm sitting at a light or a drive-through for awhile, I'll flip it on. This keeps my gauge at normal. I'm probably going to get a Griffin or other aluminum radiator soon which might negate the need for that fan, but such a purchase is expensive and I don't recommend it just because your car runs hot. Try those things out.
 
rokclimb15 said:
.......consider getting an auxiliary fan. I have a 14" fan mounted in front of my radiator that goes to a toggle switch under my dash. If I'm sitting at a light or a drive-through for awhile, I'll flip it on. This keeps my gauge at normal..............

He already has a pusher fan on the front that comes on when the car gets hot enough to kick the high speed mode on the older cars.

Go ahead and replace the tstat but unless you get a chip to lower the on temps for the fans, I would not recommend using a 180. Use the stock 195 and make sure its the ford one for our cars.

Also as suggested get a full coolant flush and new coolant 50/50 mix put in. If your doing it yourself, consider removing your radiator and hose out the rad from back to front as well as your a/c condensor on the car.... you'll be surprised how much crud comes out of the bottom of the condensor that blocks the air flow. Doing this you'll find your car runs cooler AND your a/c will actually run cooler as well :). Once you'be put everything back together, then put in a bottle of water wetter or I think royal purple ice or something like that.

Frit
 
Thanks to all of you for your responses. I flushed the cooling system, replaced the radiator and refilled with 50/50 mix distilled water and coolant about 1.5 years ago. It has been about 3.5 years since the thermostat was replaced. The first replacement radiator lasted only about 2 years before developing a leak. When I drained it it had a strange greyish-brown sludge in it. The radiator shop claimed they had never seen anything like that before, but stressed that I should fill the system with green coolant and distilled water.

If I were to replace the thermostat with a 180, does anyone have a recommendation as to where I should purchase the 180 (even better if you can recommend a manufacturer) and also which chip would work best with the 180 t-stat "out-of-the-box" without additional (or at least minimal) programming? Any idea on the cost of the chip would be much appreciated as well.

Anyone have any additional ideas on the A/C diverting to the defrost vents when in the Max position only and while accelerating but not at WOT? I don't believe it is a vacuum issue, as I am pulling 20 psi at idle in park/neutral and 17-18 psi idling with tranny engaged (the teflon I/C tube gaskets work wonders).
 
Last edited:
A little more Info on Cooling Fans

I was working on a spark plug this morning and thought I would do a little more testing on my cooling fans. I removed the puller fan from the radiator and tried spraying from back to front through the radiator and A/C condensor (as fturner had recommended, although I wasn't replacing coolant and didn't remove the radiator).

What I noticed is that with the A/C running in either normal or Max, the main puller fan (on engine side of radiator) never came on. The pusher fan (front side of A/C condensor) would cycle on and off. The engine was not up to temperature at this point.

It was my understanding from other threads that when the A/C is on that both fans should run continuously up to a speed of approximately 45 mph. I also thought that they would run after a certain temperature was reached and the car was below this speed.

I performed a KOEO self test and both fans come on at the beginning of the test before codes are sent. All codes are normal. Does anyone have any idea what might cause this behavior (the A/C is still diverting to the defrost vents under acceleration even when not wide open throttle).
 
Don't know about the fans, but on most Fords, the doors are controlled by vacuum. And usually there is a check valve on the vacuum line going into the switch block, sometimes under the hood, sometimes under the dash. If this goes bad, the vacuum will fall off and the flow will change to vents or defrost depending on how the system is designed. My dad's '87 F-150 does this under hard acceleration when vacuum falls off. I'd figure that it would be even worse on our cars due to the boost buildup. Hope this helps some.
 
>check valve on the vacuum line going into the switch block<

Anyone have a pic of the check valve, or part no.
thanks
Chris
 
Update on cooling Fans

I still have no "puller" fan under with the A/C running (or not). However, if I unlplug the ECT (Engine Coolant Temperature) sensor, the "puller" fan does come on for a short period (less than 1 minute) after the car is first started, regardless of whether the A/C is on or not and then shuts completely off. The car runs horribly at first and spits dark smoke out the tailpipes with the ECT disconnected.

Does anyone have a clue what would be preventing the "puller" fan from running at all times with the A/C on. It never comes on as best I can tell.


Thanks for any and all assistance.
 
For the A/C problem it may also be that the vaccum canister may be cracked and not holding reserve vaccum for when the engine is not pulling a vaccum.
 
Thanks for the response birds4us. Can you give me an idea of where I can locate the vacuum canister you are referring to on a '94 SC?
 
Headway on the fan issues

I believe I have determined that the low speed setting of the "puller" fan is not operating properly.

I disconnected the harness from the "puller" fan and confirmed that I had a good ground to the "black" wire in the connector. I then confirmed that the "dark blue" wire (center spade connector) is indeed receiving 12V DC at all times with the A/C turned on. It also continues to receive 12V DC for a period of time after the A/C is turned off. However, with the connector in place, there is no fan operation. I did not witness any voltage coming into the third wire in the connector "black/orange". I suspect it is the high speed supply and is what I am actually see work during the KOEO self test.

I suspect that when I perform a KOEO self test, I am seeing the high speed operation of the "puller" fan and also seeing/hearing the "pusher" fan operate.

Does anyone know a good source for a new "puller" fan motor that will work with the OEM "puller" fan and shroud assembly?

Also, can I just unbolt the motor from the "puller" fan/shroud assembly without removing the entire assembly from the vehicle (I noticed bolts going through from the engine side of the fan motor)? I don't see a good way to remove the entire fan/shroud assembly without removing at a minimum the upper radiator hose and I don't really want to break the system open since it seems to be pretty much leak tight.

All assistance is greatly appreciated!
 
Fan now working with A/C On

After some difficulty, I tracked down a new aftermarket replacement radiator fan motor for my '94 SC. I tried Autozone, NAPA, and Advance Auto Parts. Advance was the only one who listed a replacement (Factory Air manufacturer).

Their manual listed Part number 35132 as the replacment fan motor. However, it was not the correct part number. I was concerned about it when I opened the box at the store but took it home and tried anyway. It turned out to be far too shallow. It was actually the "pusher" fan replacement. After returning to Advance, their system showed no listing for the "puller" fan.

The associate got out his manual and we tried cross referencing part numbers. The Ford part number on my OEM motor was not listed, but one wit a different suffix was which turned out to be the 35132 that I had already tried.

We then looked up a '95 SC and it did list the 35132 as the "pusher" fan and listed Factory Air 35170 as the "puller" fan motor. It looked like a good replacement, same depth, same style shaft, mounting holes lined up. The only difference is that its connector is attached to a 4" - 6" harness as opposed to being built into the fan motor housing.

I have it installed and now have an operating low-speed fan with the A/C on. I have not seen the "pusher" fan operate yet with the "puller" operating. I may not be getting to a high enough temperature. Both come on during the KOEO self-test though.

This fan motor only cost $71.48 + Tax. Big difference from the Factory Air "pusher" fan motor ($128.88 + Tax) or the OEM Ford entire fan and shroud assembly ($302.00 + Tax).

Turned out that I had to drain some coolant and remove the upper radiator hose at the radiator to get the shroud assembly out to replace the motor. I first tried to disassemble in the vehicle, but the fan was stuck to tightly to the shaft. WARNING: Don't try to twist the fan on the shaft to break it free while holding the end of the shaft with pliers, etc. There is a pin going through the shaft that you can't see that a slot in the rear of the fan blade assembly engages to keep it from spinning on the shaft. If it won't pull straight off you will have to remove the assembly from the vehicle (as was my case) and then use a punch to drive the motor shaft out of the fan blade.

I applied some PB Blaster first and then put wood blocks under the backside of the shroud as close to the motor as I could without restricting its ability to drop down. With the 3 motor mounting bolts removed from the backside, it didn't take too long to drive the shaft out, dropping the old motor out. Assembly was a piece of cake.
 
Back
Top