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Topic: Manual Fan Control

in Forum: C4 Cooling and Heating Systems

Manual Fan Control

Posted: 4/4/14 1:22pm Message 1 of 18
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My C4 goes in on Monday for a manual fan control (amongst other things)

For those who have done this is there a location for the switch that would be optimal?

Obviously near the d/s seat to make it accessible, maybe near the steering column or off to the side near the hood release.

Any suggestions? 


I'm also assuming that the cooling system will function as normal with the fan(s) cutting in and out as normal, unless I override with the manual control on.

If the fan control is left on, is the circuit cut by the ignition being shut off, or should it be wired directly to the battery for control when the ignition is off?


Thanks,

 Colin.




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Re: Manual Fan Control

Posted: 4/4/14 8:02pm Message 2 of 18
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Duncanville, TX - USA
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Vette(s): 1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.
Not sure how you're going to be able to wire up a manual switch in the circuit without it being "seen" by the PCM, and setting a code. Also, sometimes wiring up one like that can cause a backfeed into the circuit, and cause more problems.
Why do you need to control the fan(s) manually, anyway? You scared of that 235* coolant temp? LOL


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Re: Manual Fan Control

Posted: 4/5/14 9:12am Message 3 of 18
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You're right about setting a code. I wired switched power to the control side of the relays and the ECM sets a code because it sees voltage when it shouldn't. It's OK as long as the ignition is "off" but easy to forget. I think the only way is to power the fans from separate relay(s) "Low speed" is sufficient for extended cool down but it becomes tricky to wire the fans in series to create the "low speed" operation without wiring issues for normal operation. Wiring a single fan on high speed from a single relay, on the other hand is relatively simple.


Re: Manual Fan Control

Posted: 4/5/14 11:51am Message 4 of 18
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Don't you mean "early on" Colin?....The fans come on too late for some folks and they wire an override to the relay.




|UPDATED|4/5/2014 11:51:22 AM (AZT)|/UPDATED|



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Re: Manual Fan Control

Posted: 4/5/14 12:35pm Message 5 of 18
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djsroknrol said: Don't you mean "early on" Colin?....The fans come on too late for some folks and they wire an override to the relay.







Yes the fans do come on late (for me) .... and I was hoping for a little manual control.


Sounds to me like a PITA if it generates a code. Have to see what the installer has in mind. Apparently he's done a few of these without issues.


A little beyond being "scared", Joel, No spring chicken any more [smile] -- but the high temps of the C4's are an eye opener for sure and I would prefer more control over that. But not at the expense of 'codes'.


I'll holler after Monday's day at the shop exactly what transpires.


Thanks for the input guys.


Cheers

Colin.




Re: Manual Fan Control

Posted: 4/5/14 12:37pm Message 6 of 18
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396c4 said: You're right about setting a code. I wired switched power to the control side of the relays and the ECM sets a code because it sees voltage when it shouldn't. It's OK as long as the ignition is "off" but easy to forget. I think the only way is to power the fans from separate relay(s) "Low speed" is sufficient for extended cool down but it becomes tricky to wire the fans in series to create the "low speed" operation without wiring issues for normal operation. Wiring a single fan on high speed from a single relay, on the other hand is relatively simple.



That may be the way to go then, 396 -- and may even be what the installer has in mind.

I'll be checking that out on Monday.

Thanks,

C.




Re: Manual Fan Control

Posted: 7/7/14 4:46pm Message 7 of 18
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|UPDATED|7/7/2014 4:46:02 PM (AZT)|/UPDATED|



Re: Manual Fan Control

Posted: 4/6/14 5:05am Message 8 of 18
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Hi Dave -- your explanation is reassuring and sounds like the job is do-able. As I mentioned b4 the installer has done some C4's b4 and apparently knows what's up......


yes I've cleaned out the debris from in front of the radiator and from in front of the condenser.

There was some but not a lot of buildup like I've read about with other C4's. Airflow at the front is on my list of regular maintenance since cooling is so critical on our cars.


About being a "hybrid" --  Is there an OBD1 code-reader available?  I'm used to having a reader available to me but understand that this is an odd circumstance and that code reading is not so straightforward.

I know there's another way of reading codes thru the ALDL and have read about that -- Not done that method b4 and would feel much more comfortable with a reader if one is available.


Thanks, Dave, for taking the time to post -- You've set my mind to rest over this install.

I very much appreciate all the help available here with a very knowledgeable C4 crowd.

You guys are the best.


Cheers,

 Colin





Re: Manual Fan Control

Posted: 4/6/14 5:47am Message 9 of 18
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Don't forget the thermostat still has primary temperature control and a high temp t'stat is going hold the temp no matter what the fans are doing. Interestingly, NASCAR engines are running much hotter than the "old days" and I understand they are using very high pressure caps to keep it from boiling. Some of it no doubt is to deal with drafting but a little higher doesn't seem to be a bad thing.


Re: Manual Fan Control

Posted: 4/6/14 10:23am Message 10 of 18
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396c4 said: Don't forget the thermostat still has primary temperature control and a high temp t'stat is going hold the temp no matter what the fans are doing. Interestingly, NASCAR engines are running much hotter than the "old days" and I understand they are using very high pressure caps to keep it from boiling. Some of it no doubt is to deal with drafting but a little higher doesn't seem to be a bad thing.



Right on 396 -- The stat was one of my first 'mods' -- putting in a 180.  I've heard that sometimes these 'stats can malfunction closed which will cause high temps .. I'm wondering what the best way is to check that the stat is functioning properly.

 The best time probably would have been b4 its install to watch it open in 180-185* water.


Can you watch the digital temp readout and garner enough info as to whether the stat opens or not?


ON a side note, the more I hear about these LT1 engines the more I realize just how tough they really are, and that they "can take quite a lickin' and still keep tickin'" ...

The higher temps seem to be normal for this engine and not as much of a stressor as I once thought.

You guys have made me much more comfortable with this engine; Now it's time to enjoy it.[smile].

C.




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