Taurus Fan Problem - Auto Elec Experts Step In

[Scottie-GNZ]

I need the opinion and advice of folks with real auto electrical experience and knowledge. This is a problem I do not want to experiment with, just to do it right.

 

I installed a Taurus fan in the following manner: 10g 12V source from a 60a fuse off the main fuse block fed by the alternator (170a). That 10g lead is Tee'd to feed low (40a) and high speed (70a VF7) relays. The high-speed relay is triggered by the ECM and the low speed relay has its ground going through a manual switch. Low-speed is only used with the switch when the engine is off in the staging area or pits.

 

When the high-speed kicks on/off, the engine stumbles badly and usually recovers after a few seconds. On occasion it will throw a code (#42 - EST Monitor Error) and sometimes when it kicks off, the engine will stall like someone plug its out of the wall. If the ECM is reset, the code 42 goes away and the engine runs like normal again. What I theorize is that the high-speed has such a high-amp draw, it is affecting all the voltage-sensitive sensors used by the GN engine management system. The ECM senses "change" and goes through it recalibration to recover normal run parameters. In some cases I believe the ECM is resetting itself or there is simply not enough voltage for the system to function when the fan kicks on/off. If I unplug the high-speed circuit and switch the low on/off, all seems normal.

 

I am concerned about damaging the system so I plan to disconnect the high-speed circuit and the manual switch and have the ECM trigger the low and hope it moves enough CFM. The little that I saw of the cooling efficiency of the high-speed, I really want to use it. So, how do I address this problem without causing damage or lot of expenses?

[wheelman]

What alternator are you running?

Is your fusebox also fed by the battery?

If not then I think your alternator is not providing enough amps to handle the startup surge of the high speed fan circuit. Try connecting the positive terminal from the battery to the fusebox feed. Use at least 10g wire and larger if you have it. This should give the fan enough juice to handle the surge without robbing the rest of the circuit. If that doesn't work then you may need to isolate the fan from the rest of the circuit to prevent the brownout condition.

 

Wheelman

[proxlamus©]

have you tried hooking it up the starter 12v source!?

 

I noticed when flipped a switch to turn the fan on high speed it took up ALOT of power.. and driving at night was very hard because the fan drained the battery soo fast and the lights were dim.

 

 

I just run it on low speed right now.. and it still has not gone over 190 F degrees

[strotter]

Though I don't know what ECU/PCM you're using, I'm surprised that you aren't also seeing an undervolt error as well. It may be possible to modify the parameters of your eeprom to reduce its' sensitivity to voltage drop - those parameters are adjustable like any other. It doesn't sound like the cpu is crashing, only dropping into limp-home. "We'll fix it in software!"

 

I have a similar, though not so extreme, problem with my '72. I'm only running a 120a alternator. The startup draw is immense, causing a significant drop in RPM, though I have never actually had the engine stall or the ecu (an older '7747) throw a code. After a few moments, the IAC catches up and all is well. I have tried setting the thing to run on "low", which is generally OK but not *quite* enough for a really hot day in stop-and-go. The startup load is significantly less in that mode, but there have been a *lot* of hot days lately.

 

Perhaps someone with some electronic experience can tell me if I could somehow set it up using a pair of relays and some kind of timer to start the fan on low, wait 5-10 seconds, and then switch to high? I'm using a Bosch 70a relay now, and have a couple more in their box - purchased with this in mind, though I don't know enough about electronic timers to work out the details. Maybe something like that can work for you?

[datsunlover]

Ok, I think I actually have an idea whats hapening.. Someone posted a link a while back about alternator wiring, and the site offers a kit or conversion I believe.. they go into a little discription of the GM alternator, and explain why a 'three wire' is better than a 'one wire' system. I was interested in it (and read through) because I was trying to figure out how to wire up my alternator (GM) to a mazda rx7... go figure..

 

Anyway.. from what I understand, the '3 wire' alternator has one wire to 'sense' voltage, and will adjust the regulator depending on demands placed on it (stereos, fans, lights, ect) basicaly changing output on the fly. The thing is, if this wire is hooked up to say.. the starter (like a typical GM would be) and you add say.. a high powered electric fan, but power it from somwhere else (battery, fuse panel, ect) it will cause problems. I don't pretend to understand this compleatly, but I assume that if the draw comes from somewhere else than the 'sensor wire' is hooked up to, it doesn't 'see' the drop in voltage, or doesn't sence it properly, causing the whole electrical system to get draged down. Even a slight voltage drop can cause sensors to missread, and the ecu to become 'confused' which seams to be what's hapening to you.

 

The site makes reference to the 'dimming light' phenomenon you see sometimes with high powered stereos in cars, which is the same effect. (you know, the civic with the huge subs, you can see the lights dim every time the subs thump) I'll see if I can find the link...

 

EDIT; Here it is... Alternator wiring site

[johnc]

I have a similar, though not so extreme, problem with my '72. I'm only running a 120a alternator. The startup draw is immense, causing a significant drop in RPM,

 

I was looking at the Taurus fan conversion then I saw the 60a draw. Jeez! Went with a nice Spal fan that pulled 2100CFM and drew 24a.

[Bartman]

The link that datsunlover posted goes to the MAD enterprises site. I spoke with Mark last week and ordered some parts from him to install my Taurus fan. He is a wealth of information, and I'm sure he could tell you exactly what your problem is and how to fix it. If you call him, make sure you have enough time because he can give you all the information you need and more.

 

He's a great guy and I highly recommend him for great advice and great parts.

[clint78z]

Sounds like you have the electrical spot on, your total electrical current is approaching the maximum capacity of the alternator. A clip on ammeter may help diagnose things. Your high speed 60a fan speed is a continous rating ?? Most time on startup there is no reverse EMF caused by the spinning motor. Most of the time startup amperages can be as much as three times the current of a normal running fan motor. Most of the time this isn't a problem lights will go dim, but electronics can act funny when getting a low voltage.

 

I would recheck the voltage regulator, dirty grounds. The physical size of the battery can act as a buffer to current flow spikes. Can you modify some of your IAC settings in the ECU, it should have a stall saver function. This will increase how fast the IAC reacts to a rpm drop at idle.

 

If all else fails an inline capacitor may solve your problems.

[Scottie-GNZ]

If all else fails an inline capacitor may solve your problems.

Is that a flux capacitor? :D

 

Please tell me a little more about the inline capacitor, what it does and any drawbacks. TIA.

[80LS1T]

An inline capacitor basicaly acts as a buffer for voltage spikes. It has to "charge up" to a certain level before it discharges the voltage. People often use them for car audio to help smooth out the voltage spikes due to the big amps used.

 

The 60 Amps that is being refered to is only on inital start up. Im not sure what the actual constant amperag draw is of the fan on high or low. I am using the one speed fan, which has performed great for me!

 

Guy

[clint78z]

Flux capacitor, that's a classic!! Actually it kinda describes what it does. It buffers wild fluctuations in the supply line. Think of your fan as the cookie monster, he has to eat so many cookies or he gets angry. The current draw is like a row of cookies going to him. If he goes on an eating binge at first he will without cookies for a while. An inline capacitor is like a big cookie jar that he is allowed to eat of directly at first and is constantly filled up.

 

Sorry for the kiddie analogy, but I like the cookie monster !!

Anyhow be sure to hook it up correctly, "don't let the smoke out". Some have polarity and some don't. Go to a specialty electronics store they should be able to help you out. Sometimes big capacitors can be found dirt cheap at an army surplus store.

 

I would recomend putting a clip on amp guage to the circuit and a voltmeter. Analyze the circuit and see what course of action should be taken. Draw a diagram of battery, alternator, fan, ecu. List voltages before and after at each one of the components.

[zcarnut]

Your problem is that during turn on the motor’s initial current surge is pulling down the supply voltage going to the ECM. This supply under voltage glitch can cause problems to the ECM even though the duration of the glitch may be very short (on the order of milliseconds).

 

When a motor is first turned on its speed is zero and therefore the “back emf†it generates is zero and the only thing that limits the current is the parasitic resistance in the circuit wiring and the motor windings. Since the parasitic resistances are purposely kept small, the resultant current is much higher than it would be under normal running conditions.

 

Wheelman is on the right track with isolation of the Taurus fan circuit. However the correct wiring procedure is to wire the fan directly from the battery positive terminal and return it’s ground wire directly to the negative battery post. In this manner you are isolating the “loop†of the fan motor circuit from the rest of the vehicle’s wiring. Always use a fused link in the positive lead for protection from a short circuit. In addition bundle the positive motor lead (the “send†lead) with the motor ground wire (the “return†lead) together to reduce the loop area of the fan motor circuit. This will reduce any EMI which can also cause ECM problems.

 

Why use this wiring circuit? Well the battery is the lowest impedance point on the 12V power supply. In a basic circuits class you are taught that an ideal battery has infinite capacitance. In the real world the battery has a very high level of capacitance so it resists voltage changes across it including glitches.

 

Twenty plus years of EE experience has shown me that most circuit interaction problems are a result of improper wiring and therefore can be repaired as such.

 

Alternators by design cannot do anything to prevent glitches. Alternators put out current under control of the voltage regulator and because of the slow response of the feedback loop the glitch is long gone before the alternator sees it.

[Scottie-GNZ]

Thanks for the feedback, all.

 

For starters I have rewired the fan circuitry so that power and ground is directly to the pos and neg terminal blocks in the engine compartment. The battery is in the rear.

[Nigel]

So, did rewiring the fan help? If that didn't do it, what happens when you switch the high speed fan with a mechanical switch like you are doing for the low speed fan? Your problem could be related to the wiring of the relay coil to the ECU... (what is an EST Monitor Error anyway?). Relay coils (and solenoids) can cause all sorts of problems for electronic circuits. They typicaly cause voltage spikes when they are shut off. However, you say you are having problems when the fan is turned on. So, it may have nothing to do with this. How do you have the coil side of the relay wired?

 

Just as a side note, I recently blew the rad fan controller transistor in my SDS ECU. I had the fan relay coil powered by branch circuit off of the main feed line to the fan. The ECU transistor grounds the coil to turn the relay on and off. Something caused the main fan power supply fuse to blow and the surge from the motor coil fed back through the ECU since it was on the same circuit, frying the transistor. I now have the relay coil powered by a circuit completely separate from the fan circuit.

 

Oh yeah, 10 AWG is typically good to around 30A. Aren't those fans rated at something like 40+ amps?

 

Nigel

'73 240ZT

[Scottie-GNZ]

So' date=' did rewiring the fan help? If that didn't do it, what happens when you switch the high speed fan with a mechanical switch like you are doing for the low speed fan? Your problem could be related to the wiring of the relay coil to the ECU... (what is an EST Monitor Error anyway?). Relay coils (and solenoids) can cause all sorts of problems for electronic circuits. They typicaly cause voltage spikes when they are shut off. However, you say you are having problems when the fan is turned on. So, it may have nothing to do with this. How do you have the coil side of the relay wired?

 

Just as a side note, I recently blew the rad fan controller transistor in my SDS ECU. I had the fan relay coil powered by branch circuit off of the main feed line to the fan. The ECU transistor grounds the coil to turn the relay on and off. Something caused the main fan power supply fuse to blow and the surge from the motor coil fed back through the ECU since it was on the same circuit, frying the transistor. I now have the relay coil powered by a circuit completely separate from the fan circuit.

 

Oh yeah, 10 AWG is typically good to around 30A. Aren't those fans rated at something like 40+ amps?

 

Nigel

'73 240ZT[/quote']

Have not tried going back to the high-speed yet because I now have another problem that has me baffled and might be related to the fan/bad running problem. Will not drive the car again until I address this problem.

 

EST is Electronic Spark Timing and I have not seen that code again since going to the low-speed.

 

The problem with the high-speed was with the fan turning on & off and the couple of times the engine stalled it was when the fan cycled off.

 

I do not believe continuous rating of the fan is more than 30A. Besides, the original fan wiring is 10g. I now have 6' of 8g from the battery source connected to 15" of 10g which is T'd to the 2 relays. The relay is triggered by the ECM fan controller and the fan has 3' of 10g to ground.

 

The problem I am now tackling is somewhat baffling. The chip by default runs in closed-loop mode but I can program it to run in open-loop. For some strange reason, in the default mode it is "stuck" in open-loop and completely ignoring the O2 sensor and not even registering the O2 cross-counts. Same results with 3 different sensors and I have checked and confirmed the O2 signal and ground wiring are good. I suspect this problem has been there all along and with the engine running so badly as a result, it made it worse with the fan voltage problem.

 

Getting very discouraged and wondering if I will even have this car ready for the SEZ!

[Nigel]

If the problem occurs when the fan is turning off, then I'll bet it's caused by the spike from the relay coil. Try connecting a diode across the coil with the cathode (end of the diode with the stripe) connected to the positive side of the coil. Does the ECU switch the coil to ground (sink current) or does it supply 12V and the coil is always grounded (source current)?

 

Unfortunately, I don't know what would be causing the ECU to run in open-loop mode...

 

Nigel

'73 240ZT

[Scottie-GNZ]

If the problem occurs when the fan is turning off' date=' then I'll bet it's caused by the spike from the relay coil. Try connecting a diode across the coil with the cathode (end of the diode with the stripe) connected to the positive side of the coil. Does the ECU switch the coil to ground (sink current) or does it supply 12V and the coil is always grounded (source current)?

 

Unfortunately, I don't know what would be causing the ECU to run in open-loop mode...

 

Nigel

'73 240ZT[/quote']

I am assuming the diode goes between the relay 87 and the fan pos. The relay has a constant ground and the ECM supplies 12v. In actuality, the ECM triggers the original GN relay and the GN relay 87 output is the trigger for my relay. So, I have a relay triggering a relay but do not see that as problem. The GN fan relay(s) wiring is complex and the ECM uses other factors besides temp like MPH, and a/c so I left it unmolested after failing to get it to work when I tried to bypass it.

[clint78z]

Seperate and eliminate are the keys to tracing problems.

You have 3 systems you are dealing with, fan, alternator, ECU.

 

First what I would do is start with the easiest thing to check the easiest things first. Check battery voltage, then check voltage output at alternator, make sure they are within 0.2v.

 

Temporarly disconnect the whole fan from wiring harness. With the car started jumper fan directly to battery with car running, does it kill the motor YES or NO. If NO there is problems in your fan wiring. If you have a voltmeter on the battery see how much voltage drops when fan is engaged. If YES there are problems in charging or ECU wiring.

 

Many times I will trace a problem from both sides starting at the battery. Narrow it to which part of the wiring is suspect.

 

Another thing you might try is to jumper a second battery in parallel with big jumper cables. If the dying engine is caused by a voltage drop, the second batter will reduce the voltage drop because it can now kick out twice the current.

 

Keep at it and be mythotical in checking, don't use the voltmeter like a white cane !!

[Bartman]

Okay I'm not an expert, but I want to wire my Taurus fan correctly. I got my parts from MAD Enterprises including his book on Electrical Wiring. From my discussion with Mark he recommended hooking the fan directly to an insulated terminal block (which I ordered from him) connected to the output of the alternator (not the battery). He said the alernator puts out around 14 volts while the battery only puts out around 12 volts, and that most electronics would prefer to use the 14 volts. I see quite a few posts recommending connecting to the battery, and I'm not understanding why. In fact, I currently have mine hooked to the battery and I don't think it's a good setup. When I turn my fan on high it actually makes my amp gauge go way over to positive charge (which from what I understand is not good).

 

Did the fan on the Taurus cars run off power coming directly from the battery? Do any other car's run their electric fans from the battery?

 

My Painless auxillary fuse block came with instructions to connect it directly to the battery as well, but after talking to Mark I think that should be connected to my new insulated terminal block as well.

[DaleMX]

My taurus fan bogs the idle to almost nothing but no voltage drop or lights are dimming, for me it's just the heavy load on the alternator bogging the engine down. I know my fan pulls like over 100 amps at startup and goes down to like 40 or so when running. The only time I have a problem is at idle. Maybe a big capicator would help keep the surge from bogging the engine.