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fans not working


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#1 valen

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Posted 03 June 2011 - 07:54 PM

Hey everyone! My fans arent working and its causing an over heating problem! I checked the relay fuses by putting them into the fog light spot. Every time i did so the fog lights worked. They worked with fan #1 relay and with fan # 2 relay and faan #3 relay. Did i check the Relays properly or is there something else i should know?

#2 GaryDoug

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Posted 03 June 2011 - 08:24 PM

Sounds right to me if you are talking about the relays. Did you check the "cooling fan" fuse too?

gallery_14511_2130_2884.jpg
1998 Trans Am - LS1/A4 - all stock - one owner - driven daily - Scan9495 author


#3 djfirebird93

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Posted 03 June 2011 - 09:59 PM

Definitely start with the Cooling fan fuse. And check the connections at each fan. Test the voltage at each connector. If there's no voltage at either connector, then it's a whole other issue.
My bird is a working progress. New Marshall engine-forged pistons, upgraded rockers and stronger rods/bearings. Rebuilt transmission. New LSD. I wish money grew on trees :)

#4 valen

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Posted 04 June 2011 - 08:09 PM

holy hell! i couldnt find the cooling fan fuse for my life. theres two fuse boxes right? where is that fuse? and what do i have to take apart to get to the connections of the fans?

#5 GaryDoug

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Posted 04 June 2011 - 08:23 PM

Here's a photo of a 98. Might be similar to your car. Note the arrow pointing to the "COOL FAN" legend on the box cover. Not sure about the cables yet.


gallery_14511_2130_2884.jpg
1998 Trans Am - LS1/A4 - all stock - one owner - driven daily - Scan9495 author


#6 Injuneer

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Posted 05 June 2011 - 05:57 AM

The fan motors are fed by a fusible link. The fan relay control voltage is protected by fuse #6 in the underhood box (which is different than the 98 and ups). Here's the diagram for your 95 (use "late production" - the switch from the "early" to "late" design was actually made in the 94 model year, not 95, but they must have forgot to change the wiring diagram).

http://shbox.com/1/1995_pcm6.jpg

Do the fans come on when your A/C is turned on? (Assumes your A/C is charged and working). What temp are you seeing on the dash gauge when you are expecting the fans to come on? Stock programming turns the fans on low speed at 226*F, and to high speed at 235*F.

For future reference, this is the 93-97 underhood box, in the lower right hand corner:

Attached Files


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#7 djfirebird93

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Posted 05 June 2011 - 08:57 AM

There should be connectors somewhere on the fans to provide power. I'm honestly not sure where the exact location is on your car, i'm not too familiar with the older models.
My bird is a working progress. New Marshall engine-forged pistons, upgraded rockers and stronger rods/bearings. Rebuilt transmission. New LSD. I wish money grew on trees :)

#8 Gearhead223

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Posted 26 July 2011 - 05:53 PM

Hey injuneer do you have that fan circuit diagram for a 2000 3.8L?

Dj the plugs for the fans are on the bottom of the fan motors.

#9 Injuneer

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Posted 27 July 2011 - 09:25 AM

GaryDoug posted a link to the 99 shop manuals, downloadable from online. That would probably be close to your 2000. Try a "search".

1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#10 bgonzalez95

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Posted 15 August 2011 - 11:20 PM

Hey everyone! My fans arent working and its causing an over heating problem! I checked the relay fuses by putting them into the fog light spot. Every time i did so the fog lights worked. They worked with fan #1 relay and with fan # 2 relay and faan #3 relay. Did i check the Relays properly or is there something else i should know?


hey did you ever find the problem?

Attached Files



#11 Syxton

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Posted A week ago

I'm having the same issue.  My A/C isn't charged so I can't test it that way.  However, we put it in diagnostic mode by grounding jumper B and both fans turn on.  They just don't turn on when the car gets hot.



#12 Syxton

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Posted A week ago

We also checked the resistance on the temp sensor on the water pump (the one that informs the ECM).  It showed about 600 ohm which I think was about right for a barely warm engine (at the time).  I pulled both ECM fuses and waited about 10 minutes, put them back in.  I'm just not sure what the next thing to check is.  We have already replaced the thermostat, thermostat housing, and temp gauge in the head (thinking maybe it wasn't as hot as the gauge was saying)



#13 Injuneer

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Posted A week ago

Did you get any codes before you pulled the ECM fuses?

 

Did you check for the 5 volt reference voltage at the water pump sensor harness connector - key on/engine off, harness off the sensor?
 

What is the dash gauge reading when the “car gets hot”?
 

600 ohms corresponds to about 146°F

 

Have you seen this:

http://shbox.com/1/4..._tech2.html#ect

 

Scroll down, there’s more than the temp/resistance chart.


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#14 Syxton

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Posted A week ago

No codes.  I haven't checked for the 5 volt reference.  Can do that today.  The gauge was right under 260 (the red) when I stopped the test.  146 degrees sounds about right.  It had been running but was cool enough not to burn.  I'll keep reading on that page, thanks.



#15 Syxton

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Posted A day ago

Ok, finally got around to doing some more work on the car.  Tested the plug to the temp sensor on the water pump.  Ended up breaking the sensor when I removed the plug (so now I have a new sensor).  The yellow wire tested with a 5V reference charge correctly.  However the black wire did not show a resistance close to zero.  It was like 128 or something around that.  After replacing the broken sensor, now the fan runs all the time when the engine is running and I got a service engine soon light.  What the heck.



#16 Injuneer

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Posted A day ago

You got a resistance on the ground wire because appears you may not have followed the instructions in the link.

 

 

The two lead connector at the water pump has a black (ground) lead and a PCM +5vdc power lead (probably yellow). Place the black meter test lead to black connector lead and the red meter test lead to the other connector lead (yellow on my 1995). You should read +5vdc because this is monitoring voltage being supplied from the PCM.

 

 

You only needed to check the voltage between the yellow wire and the black wire.  That's where you want 5 volts.  By measuring the resistance between the black wire and a chassis (if that's how you did it - unclear ?) ground, your circuit includes components inside the PCM, hence the 128 ohms.

 

Can you scan for codes?  Most likely the wire to the coolant temp sensor is not connected properly, or the sensor is defective, causing DTC 14 (shorted circuit) or DTC 15 (open circuit). 



#17 Syxton

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Posted A day ago

?? I followed the directions entirely.  I did these 2 tests.  I will check for codes in a bit.

 

Test the yellow lead by placing the DVM red lead on it and the DVM black lead to ground. A +5vdc reading will indicate the lead is ok.

 

You can test the black connector lead by using the ohms scale on the DVM. Place the DVM black lead to ground. Place the DVM red lead to the black lead of the connector. If the lead is ok, you will get an ohm reading close to zero. If you get no reading or a very high one, the lead is open or partially open.



#18 Injuneer

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Posted A day ago

The second procedure was indicated to be followed only "If you get no reading" with the first test.

 

Maybe someone else can help you.



#19 Syxton

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Posted A day ago

The code was a DCT 15.



#20 sea dog

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Posted A day ago

Have you looked code up in 93 service manual available to download at following link? Besides explaining the code, manual gives diagnostic steps. Even though manual referes to GM tech 1 scanner, you can use any obd 1 scanner that can read real time sensor data to do the tests. http://www.mediafire.../?40mfgeoe4ctti

 

If you don't have an obd 1 scanner, get the free obd 1 PC based scan program called "scan9495". It scans for codes and does running sensor scans. And logs data to a file for later use. Get the newest version in the lt1 v8 folder.  http://www.mediafire.../?0elo4c935uc5s

 

While at site download Microsoft dot net framework. It's in a folder. Also, to use program you need a cable to connect car's aldl to usb port of PC. Get a 12 pin obd 1 GM cable @ http://www.obd2allinone.com/aldl.asp

 

scan program can read sensor data with key on and engine not running. If engine won't run.

 

Also, the old obd 1 GM based scan program called "freescan" will also read codes & do running sensor scans. Do a Google search to find it.






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