Cooling Fan Diagnostics
05-13-2007, 09:55 PM
#1
Three Wheelin'
Thread Starter
Cooling Fan Diagnostics
Now that my major issues are over, I'm working on some smaller problems.
Before my tb/water pump change, the fans had decided to run on high all the time. Even before they did this, they came on late, an always high. The have never stayed on after the car is shut off.
So I've gone through Clark's, and replaced my coolant temp switch - easy diagnostics, it's always shorted between pins 1 and 3. Now I am trying to get the fans to come on at all. I haven't gotten the car hot enough to come on high, probably (haven't overheated or anything yet), but using the test procedure where I jump pins 1 and 3 of the coolant temp harness turn the fans on high. Jumping pins 2 and 3 doesn't do anything, so I went back to the resistors. They are crappy, as the battery tray used to leak, but they test good (1 ohm resistance each). The wiring looks to be OK and was all re-seated. They red/black black/red which comes from the fans themselves goes to two small black circles with 2 spade clips on each. They are labeled "TS" in the FSM wiring diagram. I don't know what they are.....diodes would make sense I guess, but they test as dead short in either polarity.
In any case, when I jump ping 2 and 3 of the coolant temp switch, I would expect that I should see voltage on the red/green and red/white leads going to the resistors, but I do not. I can however hear the relay click in the fan relay box when I bridge the 2-3 pins. I've re-flowed all the solder on the fan relay board.
When I jump the side of the resistors which come from the fan relay with 12 volts, I get slow speed on the fans.
I think I've beat this horse to death. Unless the wiring between the fan relay and resistors is bad, it has to be the relay itself.
That being said, anyone close have one, even one that I can test with? I really don't want to drop $130 or however much they are to find out I've missed something. Or does anyone else have any other test ideas? I think I've been pretty OCD about this so far, but I may have missed something.
Before my tb/water pump change, the fans had decided to run on high all the time. Even before they did this, they came on late, an always high. The have never stayed on after the car is shut off.
So I've gone through Clark's, and replaced my coolant temp switch - easy diagnostics, it's always shorted between pins 1 and 3. Now I am trying to get the fans to come on at all. I haven't gotten the car hot enough to come on high, probably (haven't overheated or anything yet), but using the test procedure where I jump pins 1 and 3 of the coolant temp harness turn the fans on high. Jumping pins 2 and 3 doesn't do anything, so I went back to the resistors. They are crappy, as the battery tray used to leak, but they test good (1 ohm resistance each). The wiring looks to be OK and was all re-seated. They red/black black/red which comes from the fans themselves goes to two small black circles with 2 spade clips on each. They are labeled "TS" in the FSM wiring diagram. I don't know what they are.....diodes would make sense I guess, but they test as dead short in either polarity.
In any case, when I jump ping 2 and 3 of the coolant temp switch, I would expect that I should see voltage on the red/green and red/white leads going to the resistors, but I do not. I can however hear the relay click in the fan relay box when I bridge the 2-3 pins. I've re-flowed all the solder on the fan relay board.
When I jump the side of the resistors which come from the fan relay with 12 volts, I get slow speed on the fans.
I think I've beat this horse to death. Unless the wiring between the fan relay and resistors is bad, it has to be the relay itself.
That being said, anyone close have one, even one that I can test with? I really don't want to drop $130 or however much they are to find out I've missed something. Or does anyone else have any other test ideas? I think I've been pretty OCD about this so far, but I may have missed something.
05-13-2007, 10:13 PM
#3
Three Wheelin'
Thread Starter
Originally Posted by V2Rocket_aka944
Could just get a lower temp thermostat...
The fans would come on high sooner, and still not run when the car is shut off, still leaving me with boiling off coolant on hot days when I park.
This car leaks enough random things. I'd like to avoid adding to that.
05-14-2007, 12:10 AM
#4
Three Wheelin'
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the old 84na with 6bl fans/shroud, the 87S and the current 951 all run on the hi speed when they come on.
the 84na would run on the driver side fan, low speed when the ignition switch was turned off to cool the water temp but the later cars never run on the low speed.
you need the low temp thermostat and switch to get the lower values.
the 951 fans come on about the middle line and i can hear them.
87951
the 84na would run on the driver side fan, low speed when the ignition switch was turned off to cool the water temp but the later cars never run on the low speed.
you need the low temp thermostat and switch to get the lower values.
the 951 fans come on about the middle line and i can hear them.
87951
05-14-2007, 09:59 AM
#6
Three Wheelin'
Thread Starter
Originally Posted by bearone
the old 84na with 6bl fans/shroud, the 87S and the current 951 all run on the hi speed when they come on.
the 84na would run on the driver side fan, low speed when the ignition switch was turned off to cool the water temp but the later cars never run on the low speed.
you need the low temp thermostat and switch to get the lower values.
the 951 fans come on about the middle line and i can hear them.
87951
the 84na would run on the driver side fan, low speed when the ignition switch was turned off to cool the water temp but the later cars never run on the low speed.
you need the low temp thermostat and switch to get the lower values.
the 951 fans come on about the middle line and i can hear them.
87951
People seem to be hung up on needing a lower temp fan switch - this is simply not the case here. I don't want to replace the wrong part to have the fans turn on high sooner and still never have a low speed setting. I want to replace teh proper part and make the car work the way it came out of the factory. If I need a lower temp switch after that, I'll do it, but right now there is a basic electrical problem with how the fan works.
