Scorpio AC fan always on

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john keefe
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Scorpio AC fan always on

Post by john keefe » Wed Apr 11, 2018 9:37 pm

TIA... so recently, the loud AC fan is operating all the time, regardless of engine temp. Its mild Winter here, so outside temp is not a factor.

At first, I thought it was the main fan clutching in on startup, but its definitely the AC fan. Cycling the climate controls does nothing, though AC will kick in properly. Short to ground somewhere? Anybody else w/ experience with this issue?

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Re: Scorpio AC fan always on

Post by brokencase » Wed Apr 11, 2018 10:27 pm

Either your condenser cooling fan relay is shorted or the condenser cooling fan temperature switch is stuck on.
Or (less likely) there may be a short somewhere in the harness to these items.
The relay is with the rest of the fuses/relay box.
The cooling switch is on the RH side of the radiator.

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Re: Scorpio AC fan always on

Post by john keefe » Sat Apr 14, 2018 12:25 pm

Thanks! I would think the temp switch is the most likely culprit, but assumed it only comes on automatically whenever AC is engaged? I'll look at my schematics.

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Re: Scorpio AC fan always on

Post by Ed Lijewski » Sat Apr 14, 2018 12:44 pm

That is the coolant fan temp switch. ( In the radiator whereas the XRs is in the lower intake manifold.) Only switches on when/if coolant temp exceeds set level, and when/if a/c pressure exceeds set level.

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john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Sat Apr 14, 2018 12:53 pm

So, you guys think that engine TCS is kaput?

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Re: Scorpio AC fan always on

Post by Ed Lijewski » Sat Apr 14, 2018 3:38 pm

Disconnect the harness from it and observe. Test the relay.

YMMV
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Re: Scorpio AC fan always on

Post by merkurdriver » Sun Apr 22, 2018 12:54 am

brokencase wrote:
Wed Apr 11, 2018 10:27 pm
Either your condenser cooling fan relay is shorted or the condenser cooling fan temperature switch is stuck on.
( x 2 )
On the relay. I've even seen the electric fan running with the car off / key out / doors locked.

john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Fri Apr 27, 2018 12:56 pm

Thanks everybody. So, its not the relays, and can't find any shorts, so must be the radiator coolant fan switch... which no one can source out here. Go figure.

Anybody have NOS, or good used? I know there's a few on eBay, but I'd rather give you guys a shot.

OR, just a thought: Has anybody by-passed the twin relay low-hi temp setup, and convert to a single low temp fan switch, like the XR4Ti, and other '80's Fords? Doesn't seem like it would be hard to do, just a concern that it might somehow conflict with the AC pressure sensing function, and screw something up... Ideas?

John

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Re: Scorpio AC fan always on

Post by brokencase » Sun Apr 29, 2018 4:18 pm

As I recall there was a TSB for the Scorpio to do the single speed setup.

There are two things that kick on the electric cooling fan.
1) A/C Pressure
2) High coolant temperature

On a Scorpio in good condition it will never kick on because of high coolant temperature.
I have never seen this happen. The engine's fan clutch always manages the engine temp fine.

Now, given the above - Here is an idea (it's not my idea - others have done this)

1) Disconnect the electric fan from radiator switch
2) Wire in a new 30 amp auto relay to the fan that triggers it off of the a/c compressor clutch.

I have done this mod (although there is nothing wrong with my radiator switch).
Your A/C will now perform much better on really hot days.

If you do this...
1) Make sure your fan clutch is good.
2) Your radiator/coolant system is good.
3) You have a functional temperature gauge.
4) You A/C system works.
5) The A/C clutch diode is in good shape and it's contacts are clean (there was a TSB about this)

The reason I mention #5 is that there is quite an inductive loading when the A/C clutch cycles with this modification.
If your A/C clutch diode is bad or has poor connections, you will notice some very strange and dangerous electrical conditions.

Finally I will have to qualify all of this with "Do this at your own risk".

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Re: Scorpio AC fan always on

Post by Ed Lijewski » Sun Apr 29, 2018 5:11 pm

John;

Your fan clutch may be failing (blades are turning but not fast enough to pull needed air through a/c condensor AND radiator).

YMMV :)
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Re: Scorpio AC fan always on

Post by john keefe » Sun Apr 29, 2018 7:29 pm

Thanks Again, Guys.
Brokencase... I'm serious considering the revised wiring, maybe even an auxiliary fan on/off switch in the cockpit, which I have as safety backup in the 5.0L XR.

Ed, I tested the function w/ Key On, Engine Off, then pulled the relay(s). Engine cold. AC fan still came on, shuts off when removing the relay(s). So, I'm guessing the belt-driven clutch fan is fine.

John

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Re: Scorpio AC fan always on

Post by john keefe » Mon Apr 30, 2018 5:15 pm

Brokencase... here's what I got from my ALLData on the Scorpio:

NOTE: VEHICLES BUILT BEFORE DECEMBER, 1987. OWNER NOTIFICATION PROGRAM (M-57) RELEASED A MODIFICATION TO THE CONDENSER COOLING FAN SYSTEM FOR ALL VEHICLES PRODUCED BEFORE DECEMBER, 1987. DURING THIS PRODUCTION PERIOD THE SCORPIO HAD A TWO SPEED CONDENSER COOLING FAN TEMPERATURE SWITCH WHICH WAS REWORKED DUE TO THE M57 OWNER NOTIFICATION PROGRAM. THIS PROGRAM AUTHORIZED DEALERS TO REWIRE THE CONDENSER COOLING FAN TEMPERATURE SWITCH TO IMPROVE INITIAL TEMPERATURE COOL DOWN CAPACITY OF THE A/C SYSTEM. THE TEMPERATURE SWITCH WAS REWIRED TO ELIMINATE THE LOW SPEED.

I'm leaning towards your simple, 2-step solution of rewiring with a 30amp relay. But, seems like this TSB solution was to eliminate the low-temp connection at the 4-pin temp sensor completely, leaving just the high temp connection?

If that's the "safer" option, I'd probably try that first. Do you have more information on the TSB rewiring procedure?

Also, could the source be a "stuck" 3-way pressure switch? This car has a Rapido replacement tank, and I assume switch et al (located to right side of coolant fan, facing vehicle).

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Re: Scorpio AC fan always on

Post by john keefe » Thu May 03, 2018 1:23 pm

Hmmm... must be an issue in the wiring harness. The only time it shuts off is when I disconnect the plug at the fan, or pull the low-speed relay (#2). Disconnected the 3-way AC switch, and the hi-low coolant temp switch at the rad, and swapped in new relays. Same results; fan still on.

Its only an issue with the "low speed" relay circuit (relay #2). Pulling Relay #3 (hi-speed) makes no difference.

Harness "wiggle test" showed no glitches. Doesn't seem a short in that harness would be a likely cause, tho. The only way the fan could get powered from a short in its power wire is if the wire was shorting to another power wire, and that would result in some other problem related to that second powered circuit. Got no other issues with the car, so rules that out?

The fuse panel is super clean above, no visible corrosion at the relay pins, and appears the grommet/seal where the panel mounts onto the firewall deck is in good shape.

EATC in the dash doesn't appear to be the problem either. Its not "stuck" on A/C mode. I get good A/C when I want, and the EATC panel will display A/C on the temp screen when on; no A/C display goes away when switched to Econ.

So... it would seem the problem must be a short in the relay connections in the fuse panel, right?

Is there any way to pull the fuse panel to get a mirror under there? Short of disconnecting all the connectors in those harnesses just to get enough slack to lift the panel.

On the fan bypass TSB... Did they just cut off the lo-speed circuit and leave the hi-speed? Or did they do the added relay jumped from the A/C clutch trick?

TIA... I'd like to avoid frying anything on this nice car.

John

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Re: Scorpio AC fan always on

Post by dimswits » Thu May 03, 2018 3:00 pm

Image

If you pull the radiator temp switch and pull the trinary pressure switch and the fan does not stop, but you pull the low speed relay and the fan does stop, then you must have a short to ground in 31B-18, the Br/Bk wire that grounds the low speed relay coil through either of those two components via splice S1024. This short could be in the fuse/relay box, but that is not likely at all.

If you visualize this wire, it is pretty long. These kinds of shorts are generally caused by two things: abrasion of the wire against a grounded part of the car, and pinching the wire by accidentally bolting something on top of it.

Follow the wire, first from the 3 way switch over to the splice behind the passenger side lights, then from there to the temp switch, then again from the splice point back towards the fuse box. Look for spots in the loom where it is pinched or worn.
Dimitri in NYC
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89 Scorpio 4.6 DOHC
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john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Thu May 03, 2018 3:41 pm

Thanks greatly, Dimitri.
Was looking over that same schematic a short while ago, but didn't see the relationship there with the 3-way pressure switch ground. I'll have at it, and let you know what happens.
John

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