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Re: toggle switch cooling fan (7/17)
 4/10/18 7:44am
eugrides
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springfield, PA - USA

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1989


Joined: 11/8/2017
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Checked manual .It's the  ac coolant fan switch that  closes at 240 psi  open 190 psi. If I jumper this switch with a toggle switch I should be able to turn fan on manually at any time. I had it backwards. has anyone tried this. I want to bring fan on before 226 deg.  
Re: toggle switch cooling fan (8/17)
 4/11/18 12:32pm
Atchafalaya
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Atchafalaya Basin, LA - USA

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I live in south Louisiana, and I like having my fans kick on sooner during our furnace months (most of the year).
I adjust all my vehicles this way...and change them during the cool/cold couple of months.
 
I suggest you spend $30. to do what you desire with an adjustable thermostatic fan control.
 
Here's one example:
 
 
Good luck.
Re: toggle switch cooling fan (9/17)
 4/12/18 4:18pm
Hot Rod Roy
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Mission Viejo, CA - USA

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eugrides said: Checked manual.  It's the ac coolant fan switch that closes at 240 psi  open 190 psi.  If I jumper this switch with a toggle switch I should be able to turn fan on manually at any time.  I had it backwards.  Has anyone tried this.  I want to bring fan on before 226 deg.  

Are you looking at a genuine FSM (Factory Shop/Service Manual) for your '89 Corvette?  Those are some strange numbers.   What refrigerant are you using in your car?

If you're using R134A, and the ambient temperature is about 75* F., you should have your system pressure cycling at a low side pressure of 35-40 psi, and your hi side at 150-170 psi.   You should never see the 190-240 psi you have referenced.   Am I misunderstanding something?

Control of your radiator fan is a separate subject.  I believe the '89 Corvette fan turn-on temp is controlled by the ECM.  Your ECM programming can be changed to lower the turn-on temperature of your radiator fan.   This will allow the fan to operate at the lower temperature, regardless of whether your a/c is on or off!  I believe your radiator fan should actuate any time your ac is operational, regardless of the coolant temperature.

The engineers at GM considered the turn-on temperature of your radiator fan to be good at 226* F.

Here's a picture of the cycling switch for your ac.  It is normally called the "low pressure" cycling switch.  If you disconnect this switch and jumper across the terminals of the connector, your compressor clutch should actuate.

/member_uploads/32201_32300/32258/342Z1_DSCN2825.JPG

Cool


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Re: toggle switch cooling fan (10/17)
 4/16/18 3:20pm
Hot Rod Roy
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Mission Viejo, CA - USA

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eugrides said: Checked manual.  It's the ac coolant fan switch that closes at 240 psi and opens at 190 psi. If I jumper this switch with a toggle switch I should be able to turn fan on manually at any time.  I had it backwards.  Has anyone tried this?  I want to bring fan on before 226 deg.  

I've done a little more research on the '89 a/c control circuit, and if I've figured it right, it seems the system is designed to turn on the radiator fan only if the a/c head pressure goes that high, which would be an unusual situation! 

Since you don't have a secondary fan in front of your a/c condenser, you don't have a coolant temp. switch (CTS) in the threaded port in your LH head, between cyl. 1 & 3.   That would be the place to install a CTS that's calibrated to the lower engine temp that you're looking for.  The radiator fan relay is located on the LH fender shield, under your master cylinder.   If you ground the control wire for that relay (I think it's the green wire), your radiator fan should come on automatically, without having to worry about a manual toggle switch!

You're probably aware that the sensor in the RH head at 6 & 8 is for your temperature gauge.

Cool



|UPDATED|4/16/2018 12:20:09 PM (AZT)|/UPDATED|


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Re: toggle switch cooling fan (11/17)
 4/15/18 1:26pm
eugrides
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springfield, PA - USA

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1989


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Reading these numbers right from FSM. these are for the HIGH SIDE of system page 8a-31.I know these numbers are high for R 12 or 134a which I now are using. I"ll probably change thermostat to 180 deg. and change coolant sensor switch to 200 -205 deg range.Thanks for your input. No aux fan.
Re: toggle switch cooling fan (12/17)
 4/18/18 2:21pm
wolfuser
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Hi,

you can fairly easily connect a manual switch to jumper the coolant temp sensor which will operate if the coolant temp reaches 240F. This is positioned at the left side of the engine and operates by connecting the lead to earth, energizing the fan relay. Thus, you need to wire your manual override so that you can provide earth when desired.

I ve routed  the wire to pass through the driver's side door seal to underneath the dashboard. earth connection was made using a redundant bracket next to the brake pedal mounting. didn t manage to get anything through the front bulkhead, which would have been first choice.

this installation works well and provides peace of mind, as the standard switching temperatures (240 on, 230 off) are very stressful for the engine esp the head gaskets.

bye
Wolfram

Re: toggle switch cooling fan (13/17)
 5/10/18 10:04pm
Hot Rod Roy
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wolfuser said:I've routed  the wire to pass through the driver's side door seal to underneath the dashboard. earth connection was made using a redundant bracket next to the brake pedal mounting. I didn't manage to get anything through the front bulkhead, which would have been first choice.

Wolfram



Wolfram, your '87 is different than eugrides '89.   His radiator fan is controlled by the ECM, so he's trying to be creative to bypass the ECM, rather than finding a way to re-program his ECM to lower the fan turn-on temp.

I believe your '87 wiring is like my '84.  My radiator fan is also controlled by a coolant temperature switch (CTS), like your '87.  I'm sure the wire thru your door gasket works, but it's a bit awkward.  If I'm right about your wiring being like my '84, there is already a wire under your dashboard where you can connect your manual switch.  It's a jumper between the top and bottom connectors to the left of your steering column.  In my '84, it's a grn/wht wire between C110-2F and C115-7E.

Green/White wire pic

Have you considered replacing your CTS with a lower temp. switch?   The ACDelco D1855B works well for me.

Cool


(large image modified to link-aapple)


|UPDATED|5/10/2018 7:04:05 PM (AZT)|/UPDATED|


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Re: toggle switch cooling fan (14/17)
 5/10/18 2:53pm
garyjackso
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Perkinston, MS - USA

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Hello to All.........  
 
What is the CTS and where do I find it?
 
 
gary


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Re: toggle switch cooling fan (15/17)
 5/11/18 3:07pm
Hot Rod Roy
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Mission Viejo, CA - USA

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garyjackso said: Hello to All.........  
 
What is the CTS and where do I find it?
 
 
gary


Gary, I explained what the CTS is in my post, but since you have a '93, you don't have a CTS (Coolant Temp Switch).   Your radiator fan is controlled by your ECM (Electronic Control Module), or whatever it's called in your '93.   This question is about the early C4 system.

Cool


|UPDATED|5/11/2018 12:07:42 PM (AZT)|/UPDATED|


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Re: toggle switch cooling fan (16/17)
 5/13/18 8:13am
eugrides
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springfield, PA - USA

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1989


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After further investigating I found I do have an aux fan and a  sensor between #1 and 3 cyl. I really just want to put a manual switch on my main fan as the aux fan is missing some screws.My Main fan relay is on left side of fan shroud. I am going to run a toggle switch to ground on ground wire  on relay and still keep wire going to computer so I can start fan sooner if I want . Any problem with that
Re: toggle switch cooling fan (17/17)
 5/16/18 11:51am
helphos
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Olney, MD - USA

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Mid America sells the switch you need  and posts the instructions for all years on their website.  The price is reasonable and if you follow their directions you can't go wrong.

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