Auxiliary fan on condenser... any idea on how it works?
#1
Zen Vet Master Level VII
Thread Starter
Auxiliary fan on condenser... any idea on how it works?
Can anyone shed some light on how this little guy functions on my 89?
I read through the FSM and found only a few references to the auxiliary fan mounted on the front of the condenser. It has 5 blades with no shroud. From limited reading, apparently there is a block sensor between #1,#3 spark plug that grounds at a certain (yet undetermined) temperature, but I have no idea.
I've never seen it work and don't even know if it does?
My main fan works as it should; it comes on at 226 w/o AC and runs continuously with the AC on.
Thanks!
I read through the FSM and found only a few references to the auxiliary fan mounted on the front of the condenser. It has 5 blades with no shroud. From limited reading, apparently there is a block sensor between #1,#3 spark plug that grounds at a certain (yet undetermined) temperature, but I have no idea.
I've never seen it work and don't even know if it does?
My main fan works as it should; it comes on at 226 w/o AC and runs continuously with the AC on.
Thanks!
#3
Instructor
In a nut shell, I removed my aux fan, I found that with out it the car runs cooler. The aux fan just blocks air from coming in, a GM fix (that did nothing) for owners complaining about the high operating temps. These temps were designed to meet emission standards at the time. PM me and I will explain what I did to keep the car running cooler. I have an 89 pushing 350 rwh.
#4
Zen Vet Master Level VII
Thread Starter
I just shot you a PM
#5
Yes - a stat on side of engine. Typically stat goes on around 240F. Replacing it with a 200 to 220 will help. The biggest problem with the C4 is at a standstill. If the front air dam has been damaged then the airflow is a short circuit. The AUX fan will help if set to come on earlier. I still have several stats for sale: $30 ea.
#6
One issue I had was on a hot day stuck in Chicago traffic jam, the a/c would stop cooling. There's simply not enough air flow through the condenser & radiator with the single fan. I don't know if the aux fan would help in that extreme situation. Once I got over 30 mph the a/c started working.
#7
Pro
Can anyone shed some light on how this little guy functions on my 89?
I read through the FSM and found only a few references to the auxiliary fan mounted on the front of the condenser. It has 5 blades with no shroud. From limited reading, apparently there is a block sensor between #1,#3 spark plug that grounds at a certain (yet undetermined) temperature, but I have no idea.
I've never seen it work and don't even know if it does?
My main fan works as it should; it comes on at 226 w/o AC and runs continuously with the AC on.
Thanks!
I read through the FSM and found only a few references to the auxiliary fan mounted on the front of the condenser. It has 5 blades with no shroud. From limited reading, apparently there is a block sensor between #1,#3 spark plug that grounds at a certain (yet undetermined) temperature, but I have no idea.
I've never seen it work and don't even know if it does?
My main fan works as it should; it comes on at 226 w/o AC and runs continuously with the AC on.
Thanks!
If you have an auxiliary pusher fan in front of the AC condenser it is controlled by coolant temp switch found between cylinders 1 & 3 in the drivers side cylinder head. It comes on @ ~238*F and off @220*F. The auxiliary fan really helps cool down the condenser in hot summer months when the A/C is running full blast. The aux fan temp switch between cylinders 1 and 3 shorts to ground at 238 F, you can buy a temp. switch that turns this fan on at a lower temp (215*F) helping to keep coolant temps much lower than the factory 238*F parameter. Other lower coolant fan temp. switches are also available. When this switch is grounded the aux fan relay coil is energized which turns the aux fan on. If you remove this switch plug and short it to ground your aux fan should begin to run if everything is in working order. I wouldn't remove it if you run your vett in the summer with the A/C blasting!
As indicated above the ECM will turn the main fan on at 228 F and off at about 210 F. The main fan is turned on by the ECM based on inputs from the coolant temp sensor, vehicle speed sensor, and the A/C coolant fan switch. This ECM controlled main fan can also be programmed to turn on at a lower coolant temperature with either a tune or a eprom (chip) that plugs into your ECM. If you decide to alter the main fan temp. turn on point you should also consider installing a lower temperature opening thermostat to compliment the lower temp fan operating temps. 165*, 170*, 180* and 195* thermostats are available to do this.
Last edited by mako41; 06-21-2017 at 07:11 PM.
#8
Pro
One issue I had was on a hot day stuck in Chicago traffic jam, the a/c would stop cooling. There's simply not enough air flow through the condenser & radiator with the single fan. I don't know if the aux fan would help in that extreme situation. Once I got over 30 mph the a/c started working.
What I would recommend is installing a lower temp coolant switch found between cylinders 1 & 3 to get this aux fan spinning at a lower temperature to keep things much cooler, and thus avoiding heat soaking the entire engine compartment!
If you go that route these are your options;
AC Delco switch part # D1855B which crosses to GM part #14043275 can be ordered thru any Chevy dealer. It is a low temp grounding switch turning the fan on at ~ 215* F and off at 200* F (Much better choice for summertime A/C operation)
Not to be confused with the OEM switch AC Delco part# D1852B witch crosses to a GM part #14043276. This is the OEM Temp grounding switch that turns the fan on ~ 238* F and off at ~220*F (This is OEM & what you have now)
If your looking for more cooling MAM (Mid America Autoworks) does sell an even lower Temp switch which will turn on at at 200* F and off at 185* F, part #609-106
Last edited by mako41; 06-21-2017 at 07:20 PM.
#9
Zen Vet Master Level VII
Thread Starter
What I would recommend is installing a lower temp coolant switch found between cylinders 1 & 3 to get this aux fan spinning at a lower temperature to keep things much cooler, and thus avoiding heat soaking the entire engine compartment!
If you go that route these are your options;
AC Delco switch part # D1855B which crosses to GM part #14043275 can be ordered thru any Chevy dealer. It is a low temp grounding switch turning the fan on at ~ 215* F and off at 200* F (Much better choice for summertime A/C operation)
#10
Zen Vet Master Level VII
Thread Starter
*update*
I ordered the AC Delco D1855B and it arrived over the weekend. I tested the Aux fan by grounding the pigtail--- it worked just fine.
I popped in the new sender with no real issues. I fired up the car and let the temp creep up. There was no leaks but the aux fan did not go on at 215. I watched the gauge climb to 226 and then the main fan went on as normal and cooled it down quickly.
Huh?
Did I get a defective unit? Is there a way to test the unit while still on the car like putting an ohm meter on the sending unit (the inside contact and the outside) and seeing if it is within specs?
BTW...The "sending shaft" that goes into the water jacket was about a 1/3 of the diameter of factory one, so clearly it is a different unit.
Any suggestions?
I ordered the AC Delco D1855B and it arrived over the weekend. I tested the Aux fan by grounding the pigtail--- it worked just fine.
I popped in the new sender with no real issues. I fired up the car and let the temp creep up. There was no leaks but the aux fan did not go on at 215. I watched the gauge climb to 226 and then the main fan went on as normal and cooled it down quickly.
Huh?
Did I get a defective unit? Is there a way to test the unit while still on the car like putting an ohm meter on the sending unit (the inside contact and the outside) and seeing if it is within specs?
BTW...The "sending shaft" that goes into the water jacket was about a 1/3 of the diameter of factory one, so clearly it is a different unit.
Any suggestions?
Last edited by billschroeder5842; 07-10-2017 at 09:54 PM.
#11
Pro
*update*
I ordered the AC Delco D1855B and it arrived over the weekend. I tested the Aux fan by grounding the pigtail--- it worked just fine.
I popped in the new sender with no real issues. I fired up the car and let the temp creep up. There was no leaks but the aux fan did not go on at 215. I watched the gauge climb to 226 and then the main fan went on as normal and cooled it down quickly.
Huh?
Did I get a defective unit? Is there a way to test the unit while still on the car like putting an ohm meter on the sending unit (the inside contact and the outside) and seeing if it is within specs?
BTW...The "sending shaft" that goes into the water jacket was about a 1/3 of the diameter of factory one, so clearly it is a different unit.
Any suggestions?
I ordered the AC Delco D1855B and it arrived over the weekend. I tested the Aux fan by grounding the pigtail--- it worked just fine.
I popped in the new sender with no real issues. I fired up the car and let the temp creep up. There was no leaks but the aux fan did not go on at 215. I watched the gauge climb to 226 and then the main fan went on as normal and cooled it down quickly.
Huh?
Did I get a defective unit? Is there a way to test the unit while still on the car like putting an ohm meter on the sending unit (the inside contact and the outside) and seeing if it is within specs?
BTW...The "sending shaft" that goes into the water jacket was about a 1/3 of the diameter of factory one, so clearly it is a different unit.
Any suggestions?
Did the Aux fan kick on at all? At what temp??
D1855B which crosses to GM part #14043275, which turns the Aux fan on at ~ 215* F and off at 200* F
Or did they give you an OEM part # D1852B witch crosses to a GM part #14043276. This is the OEM Temp grounding switch that turns the fan on ~ 238* F and off at ~220*F
Check your receipt and the actual part numbers on the switch.
Last edited by mako41; 07-11-2017 at 07:08 PM.
#12
Zen Vet Master Level VII
Thread Starter
You sure you got the right part??
Did the Aux fan kick on at all? At what temp??
D1855B which crosses to GM part #14043275, which turns the Aux fan on at ~ 215* F and off at 200* F
Or did they give you an OEM part # D1852B witch crosses to a GM part #14043276. This is the OEM Temp grounding switch that turns the fan on ~ 238* F and off at ~220*F
Did the Aux fan kick on at all? At what temp??
D1855B which crosses to GM part #14043275, which turns the Aux fan on at ~ 215* F and off at 200* F
Or did they give you an OEM part # D1852B witch crosses to a GM part #14043276. This is the OEM Temp grounding switch that turns the fan on ~ 238* F and off at ~220*F
No, the AUX fan did not come on at all. I double double checked the AUX fan and it popped right on when grounded. Since the only thing between the pigtail and a ground is the sending unit, I can only surmise that I got a defective unit or a mis marked one.
The photo on the AZ web showed that I got the correct piece for the lower temp. I ordered another one and will give it a shot.
#13
Zen Vet Master Level VII
Thread Starter
#14
Burning Brakes
Maco41 are you saying that if sensor wire is grounded that the relay will make the fan run ? This is something I would like to know. If this did work then I could ground it with a toggle switch, correct ?
Last edited by A Peter C4; 07-11-2017 at 10:19 PM. Reason: Ask more
#15
Pro
Yes if you disconnect the single OEM wire running to the temp sensor switch found between the # 1 and #3 cylinders and ground it to any nearby grounding point the Aux fan motor should begin to spin. If it doesn't you have some other problem most likely the aux. fan relay is no good. On an '89 that relay is mounted on the drivers side of the radiator shroud. And yes you could also manually ground the relay with a switch to activate the aux fan any time you want.
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A Peter C4 (07-12-2017)
#16
Pro
The box said D1855B and the 14043275B. There were no stamps on the part.
No, the AUX fan did not come on at all. I double double checked the AUX fan and it popped right on when grounded. Since the only thing between the pigtail and a ground is the sending unit, I can only surmise that I got a defective unit or a mis marked one.
The photo on the AZ web showed that I got the correct piece for the lower temp. I ordered another one and will give it a shot.
No, the AUX fan did not come on at all. I double double checked the AUX fan and it popped right on when grounded. Since the only thing between the pigtail and a ground is the sending unit, I can only surmise that I got a defective unit or a mis marked one.
The photo on the AZ web showed that I got the correct piece for the lower temp. I ordered another one and will give it a shot.
You must determine what temp the aux fan is being activated, the poster's above idea to disable the main fan until the aux turns on is a good idea. I would try it.
Let us know what you find.
Last edited by mako41; 07-12-2017 at 11:21 AM.
#17
Zen Vet Master Level VII
Thread Starter
Dumb *** question as I have no idea on how the sensor works in practice...
I'm about to swap my AC Delco D1855B for a Duralast SW505 that is supposed to be the same interchange with the AC version. As I mentioned earlier, I think the AC is bad.
So... I notice that the AC Delco version came with Teflon tape wrapping the threads while the Duralast that I picked up today had none and the factory one did not have tape either.
Could the Teflon tape effect grounding and make the sensor not read? Again I'm not sure how these damn things work.
I'm about to swap my AC Delco D1855B for a Duralast SW505 that is supposed to be the same interchange with the AC version. As I mentioned earlier, I think the AC is bad.
So... I notice that the AC Delco version came with Teflon tape wrapping the threads while the Duralast that I picked up today had none and the factory one did not have tape either.
Could the Teflon tape effect grounding and make the sensor not read? Again I'm not sure how these damn things work.
Last edited by billschroeder5842; 07-12-2017 at 07:13 PM.
#18
Instructor
Dumb *** question as I have no idea on how the sensor works in practice...
I'm about to swap my AC Delco D1855B for a Duralast SW505 that is supposed to be the same interchange with the AC version. As I mentioned earlier, I think the AC is bad.
So... I notice that the AC Delco version came with Teflon tape wrapping the threads while the Duralast that I picked up today had none and the factory one did not have tape either.
Could the Teflon tape effect grounding and make the sensor not read? Again I'm not sure how these damn things work.
I'm about to swap my AC Delco D1855B for a Duralast SW505 that is supposed to be the same interchange with the AC version. As I mentioned earlier, I think the AC is bad.
So... I notice that the AC Delco version came with Teflon tape wrapping the threads while the Duralast that I picked up today had none and the factory one did not have tape either.
Could the Teflon tape effect grounding and make the sensor not read? Again I'm not sure how these damn things work.
#19
I doubt any of the "re-sellers" are paying for closer to OE design specifications.
#20
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One issue I had was on a hot day stuck in Chicago traffic jam, the a/c would stop cooling. There's simply not enough air flow through the condenser & radiator with the single fan. I don't know if the aux fan would help in that extreme situation. Once I got over 30 mph the a/c started working.
Switching to the later two fan system might provide better cooling.