Pusher Fan doesn't come on

[RolandMD]

Hello,
I have a 95 Lumina APV - 3.8. The pusher fan does not come on. I replaced the relay and still nothing. I ran batter power to the fan and it works - so both the fan and the relay (new) are good.
I followed the test procedures from Chilton: disconnected the pusher fan relay. With the key on I probed pin 85 and 87 and have power to both. Next I am to jump pin 85 to pin 30 (which goes right to the fan motor). Since there was power at 85, the fan should run. It did not. So, problem should be between relay and fan motor.
I spliced in a new wire between the relay ( pin 30) and the fan motor (B terminal). Then I again jumped pin 85 to 30 and still nothing, even though I had power at pin 85. Then I noticed that when I jump 85 to 30, I loose all power to 85. As soon as I disconnect the jumper wire from pin 30, the power returns to 85. I am not understanding why I am loosing the battery power to 85 when I jump it to 30??

[LMP]

If you use pin 85 to feed the fan directly, you can blow the IGN fuse as this feed is for the relay coil only, a low power load, and wired with very small conductors.
A direct feed to fan should be tried only from 87 to 30.
www.avigex.ca/xport/fandiagram.jpg

INstead, I'd try to connect a wire to contact 86 while leaving the relay in place, and ground the other end of wire: this should activate the relay coil which turns the fan ON.
If fan turns ON, then the ECM logic is inhibited from turning the fan ON, either from some sensor condition, or blown trigger transistor (coolant pusher fan control), or, the 12V you find at pin 85 with a voltmeter is stray voltage even unable to feed the relay coil. HOwever, if puller fan works, this option is out as the 12v to both fan relay coils is from same source.....

ANOther possibility is failed fusible link V that feeds the pusher fan. (IF test from 87 to 30 works, then disregard this option). A failed fusible link can feed stray no load voltage but unable to deliver load current to fan....(A stray voltage is a voltage that is fed through a high resistance circuit: it will be measured by a voltmeter that uses almost no current at all for its purpose, but as soon as a real load is applied, the resistance will drop all the voltage.)

BY the way, confirm the condition you install to test both fan working.....this should happen when you turn A/C on..

[RolandMD]

Originally Posted by LMP

If you use pin 85 to feed the fan directly, you can blow the IGN fuse as this feed is for the relay coil only, a low power load, and wired with very small conductors.
A direct feed to fan should be tried only from 87 to 30.
www.avigex.ca/xport/fandiagram.jpg

INstead, I'd try to connect a wire to contact 86 while leaving the relay in place, and ground the other end of wire: this should activate the relay coil which turns the fan ON.
If fan turns ON, then the ECM logic is inhibited from turning the fan ON, either from some sensor condition, or blown trigger transistor (coolant pusher fan control), or, the 12V you find at pin 85 with a voltmeter is stray voltage even unable to feed the relay coil. HOwever, if puller fan works, this option is out as the 12v to both fan relay coils is from same source.....

ANOther possibility is failed fusible link V that feeds the pusher fan. (IF test from 87 to 30 works, then disregard this option). A failed fusible link can feed stray no load voltage but unable to deliver load current to fan....(A stray voltage is a voltage that is fed through a high resistance circuit: it will be measured by a voltmeter that uses almost no current at all for its purpose, but as soon as a real load is applied, the resistance will drop all the voltage.)

BY the way, confirm the condition you install to test both fan working.....this should happen when you turn A/C on..

Oops! My bad. It WAS pin 87 to 30. I was instructed to probe both 87 and 85 for power (with ignition on - Chiltons). I do have power at both 87 and 85. However, when I jump 87 and 30, I loose the power to 87 (I am using a voltmeter, and it reads 000). As soon as I remove the jump wire from between the two (87 &30), the power returns to 87.
Also, with the key in the on position and engine cold, I turn on the AC. According to Chilton, the puller fan should come on. It does not, yet the puller fan is the only fan that does work. Like I said, I ran direct battery to the pusher fan and it does work, and there is a brand new relay there.
Mostly I am confused as to why 87 would loose power when it is jumped to 30 (and I did splice in a new wire between the relay pin 30 and terminal B on the fan - just to be sure I had a good connection). I appreciate the help!!

[RolandMD]

OK - I re-read your response, and it seems that the fuseable link seems the likely culprit. I do have power to 87 until I try to run the fan with a jumper from 87 to 30, then 87 looses all power. As soon as the jumper wire is removed from 30, the power returns.
Question - do you know where the link is? The schematic tells me that it routes to the starter. Also, what is the best way to test it?
Thank you VERY much.

[LMP]

Originally Posted by RolandMD

..- do you know where the link is? .

..bolted to ABS enable relay...yeah...where is the ABS enable relay ??? lefthand top of suspension tower (all based on '93 service book...likely the same)

Originally Posted by RolandMD

..- Also, what is the best way to test it? .

bypass it...or run a wire direct from battery post (red plastic cover near brake booster) to pin 87.

[RolandMD]

Hi LMP,
Thanks for your wisdom. I haven't bypassed the fuseable link yet (rain), but will probably get to it tomorrow.
When I was testing the fan at the relay, I did jump pin 85 and pin 30 one time. I remember a spark. Maybe I messed something up? Before I did the checks (and the 85 to 30 jump), the van would start as soon as I turned the key. Now when it is cold it cranks for several seconds (3-5) before it finally starts. Could I have done something to have caused this by jumping 85 to 30?
Thanks again (there will be a little something extra in your check this week).
Roland

[LMP]

Overloading the IGN circuit should have no adverse effect, as the worst that can happen is blowing the fuse. In addition, this circuit is dead when ignition key is to OFF...however I have not verified the rest of components that could have operated at a low voltage for a short time when the mishap happened...would that have changed some reference point in the computer? Can't answer at this time but is it were the case, it would progressively recalibrate with time.....
Other that that, I would call it a coincidence....

[RolandMD]

OK my friend - getting interesting (& frustrating). I located the fuseable link next to the ABS relay. There are 4 fuseable links, but I isolated the link that supplies the pusher fan. What I found was that there are TWO 12 ga. red wires connected to this fuseable link, So I snipped them both, removed the link and ran the wires directly to the post (battery power). What I found was that both of these 12 ga wires each were supplying power to the pusher fan relay Even when I removed one from the post, power was still going to the relay through the other wire. With the ignition on I was getting power at the relay, pin 87 from both wires.
So, with power at pin 87, I jumped pin 87 to pin 30 - and same results, i.e. no pusher fan and the power again dropped to zero on 87. When I removed the jumper wire from pin 30, the power returned - just like before I bypassed the fuseable link.
So now I am thinking that there is a problem in the wiring between the link and the relay. So I bypassed the whole thing. I ran a new power wire from the post to pin 87 on the relay (I snipped the old power wire at the relay connector and wired in the new one). Now the power to the relay is isolated (I added an inline fuse to be safe). Now with the new power supply, I jumped 87 and 30 and the fan came on!!!!!!!
By the way, the power wire (#87) is a 16 ga. wire, and I couldn't imagine 2 12 ga. wires coming from the fuseable link supplying power to just the relay through a 16 ga. wire. So I reconnected the 2 12 ga. wires and the fuseable link back to the post - but the power to the pusher fan relay was snipped at the relay connector.
However, when I let the car warm up, the puller fan came on - but still not the pusher fan. When is this thing supposed to come on? My neighbor (who does heating and cooling) said that it is possible that with the AC refrigerant low in the system (meaning that the AC compressor doesn't come on), that the pusher fan might not come on either.
Any clues? Bueller? Bueller?

[LMP]

OK, so the 12v supply problem is now solved. Corrosion is pernicious....
Yes. a low coolant charge causing low pressure in the circuit will inhibit a/c fans ....but that does mean indeed the a/c compressor will not engage either...verify.

[RolandMD]

Originally Posted by LMP

OK, so the 12v supply problem is now solved. Corrosion is pernicious....
Yes. a low coolant charge causing low pressure in the circuit will inhibit a/c fans ....but that does mean indeed the a/c compressor will not engage either...verify.

That is correct - the AC compressor does not engage. I will put some refrigerant into the system and see what I get - and hopefully the pusher fan will work.
Thanks again for sharing your knowledge!
Roland