Low speed fan!

Digitalchaos

Registered User
Just had my A/C recharged. As I was waiting for the warm air to turn cold, I heard freon escaping from what I assume to be a pressure release valve on the compressor. Got out to investigate and assumed it to be some kind of blockage after a little trial & error. Shut it off, went for a drive, and realized after my car overheated once yesterday in 91 degrees.. the problem I thought I had a few months ago existed ; my low speed fan did not come on w/ the air, and probably hasn't been at all! :eek:

So now I need to review the possible causes of such a misnomer. I know the motor has two individual windings for low & high. Is it likely that low could burn out w/o high under completely normal stock operation?

Then there is the control box right after the bumper on the passenger side. If this was bad, what other symptoms would I notice?

Are there other, hopefully simpler, possibilities?

Tell me what you think!
 
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I had the same thing happen to my A/C except in my case it blew out all the seals and line couplings.... It didn't occur to me that the fan was required to run the A/C when I installed the adjustable cool-fan switch (live and learn). You should be able to test the fan by disconnecting the plug and running some "test" wire to a 12v source. Or, if you have a code reader, the "fan check" is one of the first diagnostic test run (at least with my cheapo WalMart code reader the fan always kicks on when I pull codes).

Either way, you don't want to try running the A/C without the fan.
 
Ok, it looks like I neglected to mention the ECT as another possibility. From what I can find, this sensor being bad would cause a loss of low speed fan operation during normal running & with the a/c on. Also it looks like unplugging it should activate the low speed fan & a check engine light if its bad. I think this is the sensor on the intake manifold with 2 wires going to it, as opposed to the gauge temp sensor which is on the other side with 1 wire. Does this sound right? I am about to check.
 
Assuming my previous assumptions were correct..

I found it :D

The fan came on immediately with the engine after unplugging the sensor. So I will go to Autozone for a new sensor, replace, and tell you what happend. Unfortunatly the plug itself looks a little worn with a small gash in one of the wire's insulation, but I think it will be fine.

Thanks for the previous posts about this topic for me to search in & find the info everyone :D

Now I just hope running it like this all this time didn't weaken my head gaskets :eek: :eek:
 
Ok, another problem.. that did not work. It is the same as before; when I have the new sensor installed & plugged in, the fan does not engauge w/ the ac. When I unplug the sensor, a check engine light comes on & the fan engauges.

Also, the new sensor is difficult to screw in when installing, after about half way on the threads. The old one was moderately difficult to remove. Should this be expected?

Any insight is appreciated.
 
Do you have a code reader? When you unplug the ECT and the fan comes on, is it the high speed or low speed? Have you tested both speeds of the fan yet?

-Rod
 
I've no code reader. I also have not tested the speeds of the fan yet; I will attempt to locate a reference for the fan plug & insert wires to connect to the battery for this.

After thinking about it, I believe the ECU gets its signal from the ECT, then directs the IRCM to engauges the fan. In which case, if the fan comes on when ECT is unplugged, ECU & IRCM I think are working properly. ECT is also working properly as it sends no error light, and I just replaced it anyway.

This leaves one unfortunate possibility right now; bad low speed motor coil. I guess the fan coming on with the ECT unplugged then in this case is the high speed.. maybe the computer defaults to high speed when no ECT is detected.

I will try to test my fan & report the results.
 
When you unplug the ECT, the EEC senses it as a very high resistance. An ECT, when operating correctly, increases its resistance as coolant temp increases. So when you unplug it, your EEC thinks that the coolant temp is very high. This would explain why it turns on the high speed fan, and why it won't start with it unplugged. If I'm wrong about any of this, please, feel free to correct me.

The first thing I'd try, is either use a code reader to see if the fan cycles through both speeds or use jumper wires to determine the same. That will let you know if the fan is at fault or not.

Also, if you just recharged your A/C and heard the freon escaping, you likely have a blown O-ring on one of the lines. I do not know of a pressure release anywhere on the A/C compressors.

-Rod
 
3 wires exist which run from the end plug of the fan to the motor. They are an all black wire, a black wire w/ yellow stripe, and black wire w/ red stripe. Plastic surrounding the plug for the all black wire has obviously been previously subject to high heat.

Am I to assume that the all black is ground, and the other 2 are for low/high operation? In which case I can connect the black to bat ground and the other two, one at a time, to bat +? Out of curiousity, which of the other two is low speed?

Thanks..
 
racecougar said:
An ECT, when operating correctly, increases its resistance as coolant temp increases. So when you unplug it, your EEC thinks that the coolant temp is very high.

Actually, ECT's (and ACT's) are reverse thermistor based. So as the temperature rises the resistance they pose decreases.

The EEC sneds out a 5 volt signal to the ECT. This signal is limited in current flow so that as the resistance posed by the ECT to current flow to ground decreases the voltage on the signal wire drops. Further the ECT circuit is dual-range. At a certain votage the current flow allowed will increase so that the voltage reading also increases similar to starting over but at a higher temp. This makes for a finer graduation.

If you watch the ECT circuit with a voltmeter on the green wire you'll see something like 2.25-2.5vdc or so cold. As the engine operates the voltage will drop until somewhere in the mid-1 volt range the voltatge will suddenly increase again and then start dropping. That would be the range switch. IIRC the voltage on the green wire will be about .6vdc at 195 and .36 at 230.

And that was waaay O/T but I'm bored :D
 
I will be testing my fan shortly. Therefore I must know if the solid black wire going to the female plug attached to the fan is not ground, and if the blck/yellow stripe wire & blck/red stripe wire are not for low & high speed.

I will be connecting it directly to the battery using bare wire inserted into the ends of the plug; so If I have the wires wrong it will fry.

For some reason, the Chilton's manual contains no information about the fan.

Thanks in advance..
 
Ok; just made some tests with a test light. With engine running A/C on, I got indication of power from male plug terminal that connects to the blue wire coming out of the IRCM. 'Twas the bottom prong of the 3. This terminal corresponds to the black w/red stripe wire connected to the fan motor.. obviously the female bottom connector. I got no power from either of the side connectors, one of which I assume is ground, the other I assume is high speed operation.

I also probed the plug for the ECT coolant sensor; engine running. I got no voltage from either of the prongs. Is this to be expected? I thought this sensor got 5 volts from the ECU, or maybe thats only if its connected.

Thanks for any help you can provide.. I will now attempt to hotwire the fan to the battery.
 
Hotwiring the fan did not work. I taped 20 guage to each battery post, then inserted negative to the recepticle w/ solid black wire & positive to each recepticle of black/redstripe & black/yellowstripe. None of this activated the fan, like it should have.

So now I need to diagnose based on the information I have thus far, and hopefully others with more knowledge can provide analysis of this information that I can not.

What I summarily have so far:

-The fan activates at some speed when I unplug the ECT sensor.
-The ECT sensor has already been targeted as a source & hence replaced.
-The fan does not activate with the A/C compressor.
-When engine running A/C running, I get a test light lighted by connecting to the blue wire (of 3 wires) going to the male plug for the fan, out of the IRCM (I think). None of the other 2 wires caused it to light.
-When probing the plug which connects to the ECT sensor w/ engine running, I get no test light. I do not know if I should.
-The car does appear to be running abnormally warm, as no fan activates until it reaches just past M in NORM. Yesterday (first day of 91d) it overheated like this.

So with this information, what do I know? Based on what I have read, I can discern that the ECU knows when I am unplugging the ECT, and is telling the IRCM to turn on either the high or the low speed fan. This implies that the ECU is working correctly, and at least one of the relays (high or low) in the IRCM is working. I also know the ECT sensor itself works, because I replaced it with an identical unit from Autozone.

I do not know which speed of fan activates when the car is running under normal conditions, and I do not know which speed is activated when I unplug the ECT. Henceforth, I do not know if the low speed relay in my IRCM has failed, or if the low speed winding on my fan motor has failed. Then again, I also do not know if the plug for my ECT has failed, as I get no indication of voltage from either of the terminals with the engine running.

So at this point, I need more information from those who know more about the electrical aspects of this vehicle.
 
Ok; myself and a friend connected a mm to various places. We checked continuity of the fan by placin gprobes in the female fan plug. Continuity was found between both side receptacles, but not when connected to the bottom prong (blck w/redstripe) which I believe is low speed.

We then checked voltage coming from the male connecter prongs out of the IRCM. The left side prong had 13 volts when I unplugged the ECT. The bottom prong had about the same when I pluged the ECT back in and turned on the A/C.

I therefore assume that the ECT being unplugged activates the high speed fan, and I know that the A/C on activates the low speed. This is how I determined that the bottom prong, blck w/redstripe on the fan, is for low speed power.

Since I had power from those 2 prongs, I now assume it can only be one of 3 things. Either a bad ground connection going to the IRCM (doubtful, but we will be checking this with mm), a bad plug connected to the fan (likely, as the high speed fan has now also ceased working after inserting probes into the plug), or a bad winding. Probably a bad winding is the problem, and I think the plug is probably also messed up.

Ok so at this point, I am assuming it is the fan & or its plug.

So I need your opinions of what I have found! If any of my statements need clarification, please do not hesitate to ask for such.

Thanks agian...
 
Problem resolved! After testing the male connector plug coming out of the Integrated Relay Control Module & finding 13 volts on both the left & bottom prong, using the right prong as our grounding point to make sure the ground hadn't gone bad, we realized it was then highly likely that the motor was at fault.

Well, during the motor continuity check, we messed the female plug for high speed by bending the contact. So we cut the plug off the fan & wired directly to the battery using screw caps & solid copper wire. The high speed turned on, and the low was dead!

to ensure the rest of the system was infact fine, and to get by until new Autozone motor, I crimped female connectors onto the bare fan wires, and plugged them onto the prongs from the IRCM plug. Left prong ground & bottom plug low speed.

It works! The fan now comes on with my A/C, and I will now be testing if it comes on at a lower engine temp than before.. which it has no reason not to.

So if you have been following this w/ these problems, use a voltage meter to check the outputs from the male connector out of the IRCM! If you get voltage, your fan motor(or its plug) is almost a garaunteed fault!

Goodluck! :cool:
 
I have completed the test drive & am happy to report that the fan now comes on at a lower temperature on the stock gauge, which is prbly 221 instead of 228! (Scary to think of how long it has been running at a temp the ECU considers overheating! :eek: )

So if anyone finds their low speed motor coils burned out, you can do what I did temporarily to provide cooling until obtaining a new fan motor. Just consider that there will be no fan, high or low, if the engine should overheat.. and this is a temporary solution.
 
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