AC Condenser Cooling Fan
-
- Level 2
- Posts: 171
- Joined: Tue Nov 24, 2020 5:32 pm
AC Condenser Cooling Fan
Hello All,
One of the modifications I installed in my car is a relay connected to the AC compressor clutch circuit to engage the electric condenser cooling fan when the AC clutch is engaged. This relay is wired into the 'low speed fan' circuit at the temperature sensor switch in the passenger side of the radiator by the horn.
However, I noticed that when the AC clutch engages and the fan switches on it is very noisy. I discovered that the fan was operating at high speed. Assuming I had a blonde moment and spliced into the wrong wire at the temperature sensor I doubled checked wiring. All was OK. I then unplugged the temperature sensor and shorted the connector pairs for the high and low speeds. It appears that the fan runs at high speed irrespective of which connector pair I use. I checked for a short between the high and low circuit back to the relay panel - nothing. An Ohmmeter check of the both the low and high speed resistance in the fan motor showed the same values for both, I would have assumed some difference in readings. For example, the two speed cooling fan on my Volvo 940 gives me two different values for the high and low speed connections.
Can anyone shed some light on this one? Hopefully I'm not having another blonde moment.
One of the modifications I installed in my car is a relay connected to the AC compressor clutch circuit to engage the electric condenser cooling fan when the AC clutch is engaged. This relay is wired into the 'low speed fan' circuit at the temperature sensor switch in the passenger side of the radiator by the horn.
However, I noticed that when the AC clutch engages and the fan switches on it is very noisy. I discovered that the fan was operating at high speed. Assuming I had a blonde moment and spliced into the wrong wire at the temperature sensor I doubled checked wiring. All was OK. I then unplugged the temperature sensor and shorted the connector pairs for the high and low speeds. It appears that the fan runs at high speed irrespective of which connector pair I use. I checked for a short between the high and low circuit back to the relay panel - nothing. An Ohmmeter check of the both the low and high speed resistance in the fan motor showed the same values for both, I would have assumed some difference in readings. For example, the two speed cooling fan on my Volvo 940 gives me two different values for the high and low speed connections.
Can anyone shed some light on this one? Hopefully I'm not having another blonde moment.
Thank you and take care,
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
Re: AC Condenser Cooling Fan
No, you are not having a "blonde moment". This fan is actually very noisy and operates only at high speed. Kicks in approximately when the temperature gauge reaches middle point and works continuously. Per Shop Manual page 36-32-3, I quote: " The condenser cooling fan system is also a backup system used to aid the cooling system when cooling system reaches high temperatures" end of quote. On the personal note: blondes are very smart.
- brokencase
- Level 7
- Posts: 1603
- Joined: Sun Dec 06, 2015 12:18 pm
- Location: PA
Re: AC Condenser Cooling Fan
The original electric fan draws an extreme amount of current (beyond 20 amps) and was originally designed to kick on only during excessive heat or when ac condenser pressures go too high. Basically in stock config it almost never turned on.
The problem you will find is that with the mod , the alternator can't keep up with the high current draw. Especially if you get stuck in traffic on a hot day with the A/C on. You can monitor this by attaching a DVM or one of those voltage readouts that plugs into the cigarette lighter. System voltage will drop to around 11 volts as you stop in traffic with the A/C on.
I have the same mod you have, but I replaced my original fan for an aftermarket fan that only draws 6 amps. It doesn't move as much air as the original fan, but it is sufficient to improve a/c cooling and I actually see coolant temp drop a little when the fan kicks in.
Totally happy with my setup now.
The problem you will find is that with the mod , the alternator can't keep up with the high current draw. Especially if you get stuck in traffic on a hot day with the A/C on. You can monitor this by attaching a DVM or one of those voltage readouts that plugs into the cigarette lighter. System voltage will drop to around 11 volts as you stop in traffic with the A/C on.
I have the same mod you have, but I replaced my original fan for an aftermarket fan that only draws 6 amps. It doesn't move as much air as the original fan, but it is sufficient to improve a/c cooling and I actually see coolant temp drop a little when the fan kicks in.
Totally happy with my setup now.
Specialization is for Insects
Re: AC Condenser Cooling Fan
For many years my A/C condenser fan kept quiet and never kicked in. Then, suddenly it came into life and now regularly engages when engine reaches normal operating temperature. I am not sure if it is due to California weather or to reduced efficiency of my radiator. When the car was about 12 years old, I have replaced OEM unit with another OEM when the engine would caused the coolant to overflow. Now, the gauge stays at normal range but occasionally goes to the letter "N" with both fans working. And yes, I did replace the fan clutch few years back.
- brokencase
- Level 7
- Posts: 1603
- Joined: Sun Dec 06, 2015 12:18 pm
- Location: PA
Re: AC Condenser Cooling Fan
Peter you need to study the relevant page in the EVTM shown below.
I think you should consider changing the three way pressure switch, or the temperature switch.
I think you should consider changing the three way pressure switch, or the temperature switch.
Specialization is for Insects
Re: AC Condenser Cooling Fan
Forgot to mention that I don't use A/C, just roll down windows. The rest works, but I always keep a watchful eye on the temperature gauge. Engine temperature sensor (not a switch) was replaced with another OEM some time ago.
-
- Level 8
- Posts: 8416
- Joined: Thu Sep 04, 2003 5:53 pm
- Location: The Belly of The Beast
Re: AC Condenser Cooling Fan
'88 and '89 fans are different. And produce different sound levels. '88 is flat bladed, '89 blades are curved within an outer edge frame which rotates as a unit. The '89 makes less noise. The two fans mount the same. But a good '89 fan didn't operate properly (retaining its OEM wiring) when mounted on my '88 so I reinstalled the original '88 fan. Both of these cars a/c systems work to my full satisfaction in cooling the interior, (immobilized or crawling forever in traffic excepted).
YMMV
YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!
Lijewski: "Sum Ergo Drive-O. Mucho!
Re: AC Condenser Cooling Fan
I guess mine is the 88 model (cannot recall if my mechanic replaced it in 92 for a newer model) as the blades are pretty flat but retain little curvature. The unit is protected by the plastic snap-on shroud and is made of black plastic. For a while I was under the impression that a three-way pressure switch could be manually activated but after a closer look I realized it was an auto-unit.
-
- Level 2
- Posts: 171
- Joined: Tue Nov 24, 2020 5:32 pm
Re: AC Condenser Cooling Fan
Hello Brokencase,
Thanks for the feedback. What aftermarket fan did you use?
Also, which 'Peter' did you mean in your reply with the EVTM diagram? My first name is also Peter.
Hello Peter,
I agree that the condenser fan is a back up for the cooling system. The circuit is designed to operate when the coolant temperature reaches 105 C / 220 F degrees and switches off at 95 C / 173 f degrees. When this happens, the cooling fan operates at 'low speed'. However, I disagree that the fan only operates in 'high'. The switch in the radiator (lower passenger side), has two sets of contacts; one set triggers the low speed relay, the other the high speed relay. When I tested my fan I placed a jumper wire across each pair of terminals in the sensor connector. Testing each pair resulted in the same (perceived), fan speed. Hence my question regarding the resistor value in the fan motor.
Appreciate the input.
Thanks for the feedback. What aftermarket fan did you use?
Also, which 'Peter' did you mean in your reply with the EVTM diagram? My first name is also Peter.
Hello Peter,
I agree that the condenser fan is a back up for the cooling system. The circuit is designed to operate when the coolant temperature reaches 105 C / 220 F degrees and switches off at 95 C / 173 f degrees. When this happens, the cooling fan operates at 'low speed'. However, I disagree that the fan only operates in 'high'. The switch in the radiator (lower passenger side), has two sets of contacts; one set triggers the low speed relay, the other the high speed relay. When I tested my fan I placed a jumper wire across each pair of terminals in the sensor connector. Testing each pair resulted in the same (perceived), fan speed. Hence my question regarding the resistor value in the fan motor.
Appreciate the input.
Thank you and take care,
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
Re: AC Condenser Cooling Fan
So there are two of us Peters. . Anyway, the Manual only states that A/C fan starts when either thing happens: temperature reaches certain level and/or system pressure goes up. There is no mention of two speed operation. I do recall one incident when my mechanic worked on the system and suddenly the fan kicked into real high speed, almost like a whine.
-
- Level 8
- Posts: 8416
- Joined: Thu Sep 04, 2003 5:53 pm
- Location: The Belly of The Beast
Re: AC Condenser Cooling Fan
Fresh Air Peter:
Please diagram in detail how you "added a relay" to the radiator switch.
Does your car actually have low and high speed fan relays?; my two do not.
The '89 EVTM wiring diagram (I don't have the '88 EVTM) and Dean's photo of the pertinent page above, show the Lo switch receiving current only from the trinary switch.
My '88 fan motor harness has a resistor spliced into one of its wires.
Peter-2; if your Scorpio were mine I'd replace the fan clutch (again). They're durable for 50K+, may last longer, or not, but since they're still easily available at modest cost installing a new one provides peace of mind and just might lower your normal coolant temp.
YMMV
Please diagram in detail how you "added a relay" to the radiator switch.
Does your car actually have low and high speed fan relays?; my two do not.
The '89 EVTM wiring diagram (I don't have the '88 EVTM) and Dean's photo of the pertinent page above, show the Lo switch receiving current only from the trinary switch.
My '88 fan motor harness has a resistor spliced into one of its wires.
Peter-2; if your Scorpio were mine I'd replace the fan clutch (again). They're durable for 50K+, may last longer, or not, but since they're still easily available at modest cost installing a new one provides peace of mind and just might lower your normal coolant temp.
YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!
Lijewski: "Sum Ergo Drive-O. Mucho!
Re: AC Condenser Cooling Fan
Thanks Ed. I already replaced the fan clutch after my mechanic reported it was malfunctioning. Per my estimate I did only 10K on it. My radiator is another story. Bought it as OEM at the Ford dealership when noticing coolant overflow on the previous one. But no denying, now it is getting pretty long in the tooth. So far in the car lifetime, I had 4 radiators including the factory installed one. My mechanic tried the aftermarket metal one but it kept busting at the metal line connecting point. After it was fixed it three times, I went back to the dealer's and bought an OEM, aluminum unit. So in the future I will be looking at possible replacement but not yet.
- brokencase
- Level 7
- Posts: 1603
- Joined: Sun Dec 06, 2015 12:18 pm
- Location: PA
Re: AC Condenser Cooling Fan
I bought the fan off ebay. I believe it was this unit.
https://www.ebay.com/itm/253923108368
Here it is installed. Some bracket engineering is required. Not too bad. As I recall most Scorpios had the two speed setting disabled as part of a TSB rework. The TSB set it to the fast speed.
Ed, what I did to run the fan whenever the AC compressor runs is as follows...
I got a 30 amp automotive relay, I spliced a wire into the A/C clutch and ran it over to the passenger side of the radiator.
The relay activates whenever the AC clutch is activated. All pre-existing functionality is preserved.
Like this..
https://www.ebay.com/itm/253923108368
Here it is installed. Some bracket engineering is required. Not too bad. As I recall most Scorpios had the two speed setting disabled as part of a TSB rework. The TSB set it to the fast speed.
Ed, what I did to run the fan whenever the AC compressor runs is as follows...
I got a 30 amp automotive relay, I spliced a wire into the A/C clutch and ran it over to the passenger side of the radiator.
The relay activates whenever the AC clutch is activated. All pre-existing functionality is preserved.
Like this..
Specialization is for Insects
-
- Level 2
- Posts: 171
- Joined: Tue Nov 24, 2020 5:32 pm
Re: AC Condenser Cooling Fan
Hello Brokencase,
Thanks for the cooling fan info. I will look into replacing mine. Your EVTM diagram is very different from mine, see below.
Hello Ed,
My car is an early 88 production (Feb or Mar), my drivers door sticker is missing due to a minor door repair during the original owners care. It has both relays in positions 2 and 3. I haven't found any hint of a TSB having been installed. Also, my assumption, based on the EVTM diagram is that the resistor is built into the motor housing like my Volvo. When I measured the fan motor resistance between the two +12V terminals and the ground showed no difference in resistance values. This puzzled me so I checked my spare 2 speed Volvo fan and it showed 2 different values. That outcome prompted me to start this thread.
My relay is wired as follows;
1. wire 54-37 (BK/Y) to the AC clutch has a wire spliced into it that feeds terminal 86 on a 40A relay.
2. terminal 85 on the relay is connected to a ground screw.
3. wire 31B-18 (BR/BK) to the cooling fan low speed relay has a wire spliced into it that connects to terminal 30 on the relay.
4. terminal 87 on the relay is connected to the same ground screw as terminal 85.
Operation - when the AC clutch is engaged, +12V is also sent to terminal 86 on the relay, this energizes the relay coil as it is already grounded through terminal 85. With the relay coil energized the contacts 30 and 87 close, this grounds the Cooling Fan Low Speed Relay coil, the relay contacts close allowing +12V from Fuse 11 to feed the low speed side of the Condenser Cooling Fan Motor.
Hope it helps. Looking forward to the feedback.
Thanks for the cooling fan info. I will look into replacing mine. Your EVTM diagram is very different from mine, see below.
Hello Ed,
My car is an early 88 production (Feb or Mar), my drivers door sticker is missing due to a minor door repair during the original owners care. It has both relays in positions 2 and 3. I haven't found any hint of a TSB having been installed. Also, my assumption, based on the EVTM diagram is that the resistor is built into the motor housing like my Volvo. When I measured the fan motor resistance between the two +12V terminals and the ground showed no difference in resistance values. This puzzled me so I checked my spare 2 speed Volvo fan and it showed 2 different values. That outcome prompted me to start this thread.
My relay is wired as follows;
1. wire 54-37 (BK/Y) to the AC clutch has a wire spliced into it that feeds terminal 86 on a 40A relay.
2. terminal 85 on the relay is connected to a ground screw.
3. wire 31B-18 (BR/BK) to the cooling fan low speed relay has a wire spliced into it that connects to terminal 30 on the relay.
4. terminal 87 on the relay is connected to the same ground screw as terminal 85.
Operation - when the AC clutch is engaged, +12V is also sent to terminal 86 on the relay, this energizes the relay coil as it is already grounded through terminal 85. With the relay coil energized the contacts 30 and 87 close, this grounds the Cooling Fan Low Speed Relay coil, the relay contacts close allowing +12V from Fuse 11 to feed the low speed side of the Condenser Cooling Fan Motor.
Hope it helps. Looking forward to the feedback.
Thank you and take care,
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
Peter
1988 Merkur Scorpio, 1988 Plymouth Caravelle (police package), 1994 Volvo 940 Turbo Wagon, 2011 Hyundai Elantra GLS Touring
-
- Level 8
- Posts: 8416
- Joined: Thu Sep 04, 2003 5:53 pm
- Location: The Belly of The Beast
Re: AC Condenser Cooling Fan
I see three sections of wire 31B-18 (BR-BK), between the trinary switch, the radiator coolant switch, and the high speed fan relay.
My only thought is that your added wire got connected to the 31B-18 (BR-BK) high speed fan relay instead of the 31B-18 (BR-BK) low speed fan relay. Or current from your installed relay is jumping to the high speed fan wire.
Re a resistor for the low speed fan mode, it cannot be in the motor as the fan could then only run at that resistor-installed speed. There could not be a high speed motor function with a low speed resistor built into the motor.
I believe on my '88 between the fan motor harness connector and the fan motor, the hot or power wire splits into a Y with one leg having a resistor spliced into it, for the fan low speed mode. Memory fades, so maybe the arrangement has a dedicated low speed/resistor wire as part of that harness. (I do clearly remember one occasion of high ambient temperatures hearing the fan run on low speed while I was outside the car.) But in any case I think that is where on an '88 one might find a resistor. However as your car has both high and low speed relays, the necessary resistor could well be in the harness closer to the relay/fuse box. And then that would explain why your testing for resistance at the fan motor showed no difference in readings.
YMMV
My only thought is that your added wire got connected to the 31B-18 (BR-BK) high speed fan relay instead of the 31B-18 (BR-BK) low speed fan relay. Or current from your installed relay is jumping to the high speed fan wire.
Re a resistor for the low speed fan mode, it cannot be in the motor as the fan could then only run at that resistor-installed speed. There could not be a high speed motor function with a low speed resistor built into the motor.
I believe on my '88 between the fan motor harness connector and the fan motor, the hot or power wire splits into a Y with one leg having a resistor spliced into it, for the fan low speed mode. Memory fades, so maybe the arrangement has a dedicated low speed/resistor wire as part of that harness. (I do clearly remember one occasion of high ambient temperatures hearing the fan run on low speed while I was outside the car.) But in any case I think that is where on an '88 one might find a resistor. However as your car has both high and low speed relays, the necessary resistor could well be in the harness closer to the relay/fuse box. And then that would explain why your testing for resistance at the fan motor showed no difference in readings.
YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!
Lijewski: "Sum Ergo Drive-O. Mucho!