fans dont work on 90
Thread Starter
Instructor
Joined: Mar 2004
Posts: 141
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From: Burbank IL
fans dont work on 90
i was reading the service manual and it said to ground the A and B ports an the connector under the dash. both fans went on. does anyone know what would cause the fans not to go on by themselves.
thanks mike
thanks mike
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
What you did proves the fans, relays, and fusible links are working properly. It's most likely your temp switch located up front just below throttle body beside themostat housing. Drain a bit of coolant before removing it or be ready to mop some up afterwards. 
Team Owner
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From: SE NY
Cruise-In II Veteran
Both of your fans are controlled by the ECM, since they came on when you jumpered ALDL pins A&B all is well.
The stock setting for fans is to come on over 200 deg F. (around 210-220 I think). You can change that setpoint with a custom EPROM in the CalPac or you can install a manual fan switch.
The stock setting for fans is to come on over 200 deg F. (around 210-220 I think). You can change that setpoint with a custom EPROM in the CalPac or you can install a manual fan switch.
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by 65Z01
Both of your fans are controlled by the ECM, since they came on when you jumpered ALDL pins A&B all is well.
The stock setting for fans is to come on over 200 deg F. (around 210-220 I think). You can change that setpoint with a custom EPROM in the CalPac or you can install a manual fan switch.
The stock setting for fans is to come on over 200 deg F. (around 210-220 I think). You can change that setpoint with a custom EPROM in the CalPac or you can install a manual fan switch.
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Joined: Sep 2000
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From: The Top of Utah
Originally Posted by skateparkdave
If the temp switch isn't telling ECM to ground the fan relays then all can be well from ECM on but not work due to the switch.
How hot are you getting the engine in order to determine that the fans aren't working? On my car (1984) the main fan doesn't kick in until about 225* (stock).
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Thread Starter
Instructor
Joined: Mar 2004
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From: Burbank IL
i started the car a few days ago and left it runing in idle waiting for a lean oxigen check light to come on like usual i went in the house for maybe 30 min then come out and its smoking with a hole in the side of the coolant surge tank. also i tried grounding the cooling fan temp switch and they didnt go on.
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by CFI-EFI
If the ECM temperature sensor were bad, the engine would run poorly. It might never go into closed loop, it would either exhibit a fast cold, idle when warm, or have no cold idle when cold.
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Race Director
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From: The Top of Utah
Originally Posted by skateparkdave
I'm wondering if that could be the one that also affects the closed loop thing.
Originally Posted by canon1414
i started the car a few days ago and left it runing in idle waiting for a lean oxigen check light to come on like usual i went in the house for maybe 30 min then come out and its smoking with a hole in the side of the coolant surge tank. also i tried grounding the cooling fan temp switch and they didnt go on.
Depending on the year of your car, I think you were grounding the dash gauge sending unit. You can have someone watch the gauge when you do it again. Most L98's have the aux fan switch on the left side. Try grounding that wire.
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Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by canon1414
the one i was testing was on the right side right behind the oil dip stick.
The one for the fans is up front just under the throttle body. Remove the plastic acordian from TB and you will see it. It's simular if not identicle to the one by dipstick.
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by CFI-EFI
I'm sure that the main fan is controlled by the ECM, and that the ECM has only one source of engine temp information. Do we even know what year this car is? I am relying on 65Z01's comment, that since both fans came in the diagnostic mode, that the ECM controlled both fans. That makes me believe it is a newer model. The cars I am most familiar with have the main fan ECM controlled and the aux fan controlled by the fan switch in one of the heads. Which head changes by specific model year. The sensor in the other head is, as you say, for the dash gauge.
The ECM does control the fans but relies on the sensor to tell it to do so. Jumping A to B just simulates the sensor then the ECM grounds the fan relays switching the power the relay is holding at bay on to the fans.
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by canon1414
so you think i need a new sensor or could it be a bad wire going to the sensor and it is the sensor in the front of the motor.
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From: SE NY
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Jumper ALDL pins A&B and start the engine.
Watch the SES flash rate for a minute or two.
Initially it should flash at about 2Hz, while the ECM is in open loop mode.
Eventually the ECM will go into closed loop mode and the flash rate will slow to 1Hz...if both the O2 sensor and the coolant temp sensor (under the TB in the intake base) are ok.
This will verify if the ECM is getting good coolant temp data from the sensor.
If you suspect the coolant temp sensor you can measure it's resistance cold and hot. It should read several hunderd k Ohms cold and a few hundered Ohms hot.
Watch the SES flash rate for a minute or two.
Initially it should flash at about 2Hz, while the ECM is in open loop mode.
Eventually the ECM will go into closed loop mode and the flash rate will slow to 1Hz...if both the O2 sensor and the coolant temp sensor (under the TB in the intake base) are ok.
This will verify if the ECM is getting good coolant temp data from the sensor.
If you suspect the coolant temp sensor you can measure it's resistance cold and hot. It should read several hunderd k Ohms cold and a few hundered Ohms hot.
Melting Slicks
Joined: May 2004
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From: Lufkin Texas
St. Jude Donor '05-'06
Originally Posted by canon1414
how do you watch the ses flash rate with a meter or is their a light
thaks
thaks
Team Owner
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From: SE NY
Cruise-In II Veteran
With ALDL pins A&B jumpered, when you start the engine the ECM will go into field test mode and flash the Service Engine Soon light as described.
Give it a try, you will see what I mean.
Give it a try, you will see what I mean.
Thread Starter
Instructor
Joined: Mar 2004
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From: Burbank IL
i jumped the A&B like you said it started blinking i left for a minute then started backing down the driveway and it stoped and stayed off. i took the wire that i grounded it with off and the service engine light came on and stayed on.