Scorpio AC fan always on

Scorpio / Scorpio Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Wed May 09, 2018 5:00 pm

Hmmm... had a draft, but lost it.

Just FYI, I'm not recommending that relay be replaced with a fuse, just that it's not much different.

I'm also wondering if this relay setup might work better if the power to pin 30 came from the lead to the compressor clutch, instead of before the diode.

Ed, build date was 3/'88, so probably mid model year. Has the flat blade fan, not the spiral. I have two spirals on the 5.0XR, and these are quiet... one of the reasons I used a lighted over-ride fan switch in-cockpit, so I can be sure the fan's coming on, even if its just powered off the temp sensor circuit.

Are all these fans "two-speed" capable? Mine has the same part number as my other XR fans.

brokencase... if you had your 'druthers,' would you have added an additional manual rocker switch for the fan, instead of having to turn the A/C on every time?
Although I kinda' like the 2.9L now, power is an issue with the A4LD slipping now and then. Don't know if additional load, or electrical surge would be tolerable. Turbo would be nice and solve everything, but then I'd have to find a better trans. solution.

Ed Lijewski
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Re: Scorpio AC fan always on

Post by Ed Lijewski » Wed May 09, 2018 5:49 pm

After years of driving my Scorpio using a simple soft push on the accelerator from a stop to get up to speed, I realized that the trick to tap into the 2.9's (limited) "beef" is to get the car moving enough in first gear so that as it shifts into aecond gear the engine is into a meaty part of its torque curve; and ditto into third gear if road ahead is clear---> revs rise only up ~ 3500 max, but the car moves out so much quicker and smoother than with the soft accelerator push from dead stop.

I also found that assuring that distributor timing is spot on is important. Sounds like "Doh!", but don't take it for grsnted; verify it's on spec. Mine wasn't but I assumed it was...

Highly, highly recommend Lubegard trans additive. And a trans fluid cooler install. Years ago because of a fan clutch failure while the coolant temp sensor had also been faulty the trans fluid also overheated. I had a fluid flush; but also added Lubegard to it. Over time my trans function returned to better than normal (true!), with no slipping, no flaring, just crisp and confident shifts. (I also installed a new vacuum modulator).

http://www.lubegard.com/~/C-112/LUBEGAR ... Protectant. Check out all other Lubegard trans products as well.

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

john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Wed May 09, 2018 8:00 pm

Not sure I want to trust a full trans fluid flush, at least not from a pressurized system. Maybe the simple old-out/new-in flush using the tranny's pump.

Have never tried Lubegard, but people swear by it. Already have a cooler, revised pump channels, new front seal, modulator, checked linkages and kickdown, etc., etc.. So, maybe worth a try. Hasn't gotten any worse, just acts up at the wrong stoplights.

brokencase
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Re: Scorpio AC fan always on

Post by brokencase » Thu May 10, 2018 1:12 pm

I like the AC clutch mod as is and have no desire for a manual override switch.

As far as my implementation of the mod goes, I have the extra relay near the passenger side of the radiator near the switch and I ran the wire from the AC clutch across the sheet metal that goes across the front of the car where the hood latch is. As I recall the relay grounds one of the wires in the temp switch on the radiator. The radiator switch does the same thing and either can activate the fan. So normal function of the fan is not altered.
FWIW, I have never seen the fan activate because of the coolant switch.

The best thing to avoid a Scorpio engine overheat is to...
1) Make sure you have a good mechanical fan clutch.
2) Make sure your temp gauge works
3) Make sure the coolant level sensor works.
4) Make sure you thermostat is good.

I have the flat blade fan, but noise is not an issue. If I have the AC on then my windows are probably shut. The blower vent noise with the AC on max is so much louder than anything else. I just crank up the Kenwood...and ignorance is bliss.

I also have Lubeguard in my trans.

Ed Lijewski
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Re: Scorpio AC fan always on

Post by Ed Lijewski » Thu May 10, 2018 3:04 pm

Anecdote: Last mid-summer on a short city errand with a/c on the temp gauge began rising past mid to 3/4 point. I knew something was amiss, so nursed it home where the needle reached the top with red warning light lit . Couldn"t be not-long-before-inatalled new fan clutch; might be bad temp sensor (new, installed about same time as fan clutch) or connection (never was pleased with the OEM mushroom cap connector which had some slop), and shouldn't be the Motorcraft t-stat which didn't have 5-7 K miles on it over a few years.

Decided it must be the t-stat. Installed a new Motorcraft t-stat. All was and remains well. But the failure of the "young" t-stat remains puzzling.

Also renewed my stash of Motorcraft t-stats.

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

john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Fri May 11, 2018 12:14 pm

Thanks Guys,

I think this arrangement is probably doing the same thing as what you wired up. Fan comes on when I start the A/C, and cycles on and off, so its not really by-passing the compressor clutch circuit.

My temp gauge seems fine. Gradually gets to about 5/8 of the normal range as the car warms, then stays there. Never gets into high, but I understand from everyone else's issues that its not very trustworthy. Jeff's sending me a spare 4-pin temp switch, and I'll swap that out to see if the fan kicks on with engine temp.

I put a lighted fan switch in the XR, which lights up whenever is powered up, even if I'm not manually flipping it on. I'll go for similar with the Scorpio with a spare fog light switch. At least, if my temps seem to go up, and the FL switch isn't lighting up, I'll know to hit the fan manually.

brokencase
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Re: Scorpio AC fan always on

Post by brokencase » Fri May 11, 2018 1:07 pm

John check the link below about how I made a better temp gauge solution for the Scorpio...

http://forum.merkurclub.com/forum/viewt ... 5&start=15

john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Sat May 12, 2018 4:25 am

Yep, saw your post on that a while ago. Pretty damn impressive. A little out of my league, though. I don't have the EE skills to follow. Whenever I get to the "tables," I can't picture it somehow, and my brain shuts down. :D

I'll give it another read-through.

Ed Lijewski
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Re: Scorpio AC fan always on

Post by Ed Lijewski » Sat May 12, 2018 7:03 am

Ditto. :headbang

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

brokencase
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Re: Scorpio AC fan always on

Post by brokencase » Sun May 13, 2018 6:11 pm

Let me tell you what I notice having lived some time with a well calibrated temperature gauge....

I have a 185F thermostat installed. Regardless of ambient temps, if I am moving along at a reasonable speed the gauge will read 185F.

During my commute I hit some long lights. As I sit it traffic I notice the temp climbs to about 190-195F. This will quickly drop back down to 185F once I start moving again (within about a mile after leaving the slow traffic)

If i turn on the A/C (and hence the radiator efan turns on) the temp will drop to 185F - and it will stay there - regardless if I am moving or stuck in traffic.

john keefe
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Re: Scorpio AC fan always on

Post by john keefe » Tue May 15, 2018 10:45 pm

Thanks for all the advice, you guys!

I'm starting another thread, speaking about flushing the A4LD & using the Lubeguard... If you see it, any comment would be appreciated.

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