"A/C electric fan on when A/C Clutch on"

Scorpio / Scorpio Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
Ed Lijewski
Level 8
Posts: 7119
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

"A/C electric fan on when A/C Clutch on"

Post by Ed Lijewski » Sat Apr 13, 2019 5:53 pm

Brokencase; As the IMON archives haven't been available for many moons, please cut&paste that how-to blurb.

I'm not intending to do it to my Scorpios; I just want to know the steps outlined.

Reasons I won't do it are the constant battery draw with a/c On and fan motor wear, and that while in motion, especially on highways, the electric isn't likely needed at all.
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

brokencase
Level 4
Level 4
Posts: 348
Joined: Sun Dec 06, 2015 12:18 pm
Location: PA

Re: "A/C electric fan on when A/C Clutch on"

Post by brokencase » Sun Apr 14, 2019 3:32 pm

Below is the post from the IMON archives...


But i think I can explain better if I mark up the schematic from the manual.

I strongly recommend that you remove the original condenser electric fan and install one of these...

https://www.ebay.com/itm/14-inch-Univer ... SwHoFXvQWh

The original fan draws something like 20 amps. While it does a great job cooling, it draws more current than the Scorpio's
electrical system can manage in the more continuous duty that this mod results in. The above unit draws only 6 amps and still moves plenty of air and is easy to mount with a few home brew brackets. You original fan is probably getting old and tired anyhow.

So - in the schematic below, you run a wire from the hot side of the a/c clutch and you add a new relay (the leftmost relay in the picture)
So when the a/c clutch goes on it activates the relay which then applies 12v to the fan. All original functionality of the other items that
turn on the fan are left intact.

I mounted the relay on the passenger side of the radiator. I ran the "green wire" across through the metal work where the hood latch is located.

I also recommend that you put in a new A/C clutch diode when you do this mod. Make sure you solder the new diode in place and do not use "crimped' or "push on" connectors.

Image



=========================================================================
Date: Thu, 3 Sep 1998 10:12:44 -0500
Reply-To: Peter Keun <Peter_Keun@SONY.CA>
Sender: The Merkur Owners List <MERKUR-OWNERS@HOME.EASE.LSOFT.COM>
From: Peter Keun <Peter_Keun@SONY.CA>
Subject: Scorpio - Electric Cooling Fan
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII

There was a post yesterday from Todd McCracken regarding the electric cooling
fan on the Scorpio.

This fan, located in front of the condenser, is a two speed unit controlled by
two sensors and two relays. One sensor is located in the passenger side rad tank
near the bottom just in front of the 'horn that always works'. This sensor
triggers the low speed fan if the temp reaches 105C (220F), and off again when
it drops to 95C (173F). This same sensor has a second higher trigger point
(can't recall the temp), that kicks in the high speed if the coolant temp goes
over 105C (220F). The second sensor is located on top of the receiver/dryer (in
front of condensor, driver's side - long black cylinder with sight glass on
top). This sensor turns on the fan (low speed only), if the A/C pressure reaches
1703 kPa (247 psi), and switches off at 1303 kPa (189 psi).

On design flaw in the Scorpio A/C system is the fact that the fan does not
automatically kick in when the compressor engages. This is not a cause for
concern at speeds over 60kph (40mph), at slower speeds in hot weather this can
place a great deal of stress on the compressor. Head pressure can climb
dramatically which translates into reduced compressor life, added load for the
engine, and less cooling from the A/C. I have modified mine by adding a relay
that is triggered by the A/C clutch circuit and grounds the low speed side of
the rad tank switch. Big improvement in cooling (engine and you), on hot days in
stop and go traffic. (I believe FLM issued a bulletin for this mod)

Due to the location of the fan and the fact that it rarely sees any action
causes the bearing surfaces to dry and/or corrode. Best way to test is to spin
the plastic hub - there should be a slight amount of drag but a good spin should
allow the fan to continue turning for a few revolutions. If it drags, try
sliding the hub back and forth as well as in a slight circular motion to see if
you can free up the bearings. If this proves unsuccessful you will have to
remove the fan, disassemble and lubricate. This is all quite straight forward
the only potential headaches are the steel mounting bolts corroding themselves
into the alloy support frame (may have to drill out the broken piece and re-tap
or use short bolt/nut combo), and removing the 2 left hand bolts (tight spot).

Hope it helps and take care,
PKC

john keefe
Level 3
Level 3
Posts: 220
Joined: Sat Sep 02, 2006 1:13 pm

Re: "A/C electric fan on when A/C Clutch on"

Post by john keefe » Mon Apr 15, 2019 2:14 am

Brokencase, would you recommend a combo like this to replace the stock radiator flex/clutch-fan?

https://www.ebay.com/itm/251766478522

That's pretty damn inexpensive, compared to the double puller I had to use for the 5.0L XR. Connected them to a stock XR fan temp/switch drilled & tapped into the radiator, & it works great; added a secondary cockpit-activated switch, just in case. Very quiet as well. For the Scorpio, I assume the same setup would work with an XR 190-195 deg. fan switch, maybe use one of the abandoned trans-cooler line nuts/receivers in the rad, since I bypassed all that with a dedicated 5.0L trans cooler. How would you approach it?

brokencase
Level 4
Level 4
Posts: 348
Joined: Sun Dec 06, 2015 12:18 pm
Location: PA

Re: "A/C electric fan on when A/C Clutch on"

Post by brokencase » Mon Apr 15, 2019 7:12 pm

I don't recommend removing the clutch fan and switching to electric fans...unless you have upgraded the alternator.

john keefe
Level 3
Level 3
Posts: 220
Joined: Sat Sep 02, 2006 1:13 pm

Re: "A/C electric fan on when A/C Clutch on"

Post by john keefe » Sun Apr 21, 2019 3:44 am

Thanks Brokencase, didn't see the write-up on the alternator upgrade until recently... now I get it.

Merkurfast
Level 1
Level 1
Posts: 89
Joined: Tue Feb 06, 2007 9:28 pm
Location: Queen Creek, AZ
Contact:

Re: "A/C electric fan on when A/C Clutch on"

Post by Merkurfast » Wed Apr 24, 2019 1:29 pm

How about using a manual switch. What would be the best way to wire it?

my8950
Level 5
Level 5
Posts: 709
Joined: Wed Jan 19, 2005 11:07 pm
Location: Detroit

Re: "A/C electric fan on when A/C Clutch on"

Post by my8950 » Wed Apr 24, 2019 3:34 pm

Merkurfast wrote:
Wed Apr 24, 2019 1:29 pm
How about using a manual switch. What would be the best way to wire it?
You could do a manual switch as an over-ride...But, keep it tied to switched ignition. I see a lot of people who put their cooling fans on manual switches, then complain when they burn a head gasket because the car over heated, or that it wont start because they ran the battery down due to forgetting to turn off the switch. Also a guy sold a car like that, didn't inform the buyer and blew it up by the time he got home from the purchase, car never ran again after that...

Merkurfast
Level 1
Level 1
Posts: 89
Joined: Tue Feb 06, 2007 9:28 pm
Location: Queen Creek, AZ
Contact:

Re: "A/C electric fan on when A/C Clutch on"

Post by Merkurfast » Thu Apr 25, 2019 1:34 pm

How could this be incorporated in the above wiring diagram?

Brokencase how well does this fan fan on ebay flow compared to stock?

User avatar
andyofcolumbusmerkur
Level 3
Level 3
Posts: 290
Joined: Mon Jul 15, 2013 7:58 pm

Re: "A/C electric fan on when A/C Clutch on"

Post by andyofcolumbusmerkur » Thu Apr 25, 2019 4:09 pm

The infamous ebay fan fan. They flow better sometimes, worse other times. Really bad if they burn out.
You can barbecue it, boil it, broil it, bake it, saute it. There's shrimp kabobs, shrimp creole, shrimp gumbo, pan fried, deep fried, stir fried, pineapple shrimp, lemon shrimp, coconut shrimp, pepper shrimp, shrimp soup, shrimp stew, shrimp salad, shrimp in potatoes, shrimp burger, shrimp sandwich....

brokencase
Level 4
Level 4
Posts: 348
Joined: Sun Dec 06, 2015 12:18 pm
Location: PA

Re: "A/C electric fan on when A/C Clutch on"

Post by brokencase » Thu Apr 25, 2019 7:44 pm

The stock fan moves quite a bit of air. But it is irrelevant. In the original stock configuration the fan practically never came on. The Scorpio relies on the clutched mechanical fan for engine cooling.

We are not talking about engine cooling here we are talking about A/C condenser cooling.

In the course of owning two Scorpios I don't think I have ever noted a time when the original fan activated.
It's infrequent duty cycle means that most of the original fans have frozen up and don't work anyway.

The original fan draws over 20 amps when it runs. The stock Bosch alternator can't keep up with it. I ran this mod with the original fan and monitored the battery voltage with a meter that plugs into the cigarette lighter. On a hot summer day with the A/C running I could watch the battery voltage drop on my 20 minute commute. System voltage would drop to 11.2 volts as I sat in idle traffic.

The aftermarket fan from ebay works fine. It moves more than enough air to cool the condenser and even lowers the coolant temp a bit.
On a hot day I can turn on the A/C and see the temp gauge drop slightly. If you question the quality of the ebay fan then fine - go buy a Hayden or whatever you like. I put my ebay fan in last spring and it is still working. If it fails you'll hear about it here. But at a little over $20 I am happy to replace it every 3 years should it come to that - but I don't think it will.

It is a choice between an over kill fan that never came on versus a better matched fan (with this mod) that comes on when you need it - like when your stuck in traffic on a hot day and you want cool air from your A/C.

I'll take some pics of my ebay fan installation this weekend and post.

Ed Lijewski
Level 8
Posts: 7119
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

Re: "A/C electric fan on when A/C Clutch on"

Post by Ed Lijewski » Fri Apr 26, 2019 7:53 am

The Scorpio electric fan operation is controlled by either (or both) of two switches: through the trinary a/c switch: high a/c pressure activates it; as does high coolant temp via the radiator coolant temp switch.

The fan activated on low speed once on my 88 Scorpio in summer temps due to bad fan clutch (at that time the coolant temp indicator in the IP was erratic...no longer). That episode demonstrated the coolant sensor was okay.

But, as on XR's e.g., coolant fan switches fail (they activate the electric radiator fan), from overuse/age. There's no logical reason to assume the Scorpio radiator coolant fan switch is always or was always operating as designed, or at all. Unless it's tested, or new.

Fan clutches should be routinely replaced after say ~50K miles. A good new fan clutch should pull a fair amount of air through the condensor with a/c running at idle even in warm temps.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

Ed Lijewski
Level 8
Posts: 7119
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

Re: "A/C electric fan on when A/C Clutch on"

Post by Ed Lijewski » Tue Apr 30, 2019 3:43 pm

I just installed a new fan clutch on a low miles Scorpio with all service receipts, none of which showed a prior fan clutch replacement.

I decided to replace the fan clutch after observing that at idle after fully warmed up the fan moved less air than at idle when full cold. In effect the reverse of what is expected.

Indeed the new fan clutch moves significantly more air after fully warmed up, exactly what I looked for.

My experience after a couple of fan clutch swaps for new units is it doesn't pay to assume the installed unit is working as it should. New units are relatively inexpensive, and installed new units provide peace of mind that both cooling performance and a/c performance should be in spec.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

john keefe
Level 3
Level 3
Posts: 220
Joined: Sat Sep 02, 2006 1:13 pm

Re: "A/C electric fan on when A/C Clutch on"

Post by john keefe » Thu May 02, 2019 1:43 am

So, what brand of fan clutch is best, most reliable? Hayden, GMB?

Ed Lijewski
Level 8
Posts: 7119
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

Re: "A/C electric fan on when A/C Clutch on"

Post by Ed Lijewski » Thu May 02, 2019 2:28 pm

Dunno. I installed a GMB. Lower price. Also is a smaller and lighter unit (less rotating mass). Could be newer technology; or not.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

brokencase
Level 4
Level 4
Posts: 348
Joined: Sun Dec 06, 2015 12:18 pm
Location: PA

Re: "A/C electric fan on when A/C Clutch on"

Post by brokencase » Fri May 03, 2019 8:39 pm

Ditto... here. I put a new fan clutch in when I bought my Scorpio at the end of 2015. At that time RockAuto had them on clearance for $24.
I think it was the four season unit.

IMHO - the original equipped clutches did not last very long. I know of at least three Scorpios where they had to be replaced.

Post Reply