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1988 dual cooling fan operation once more

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1988 dual cooling fan operation once more

Old 06-18-2018, 06:22 AM
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Join Date: Mar 2018
Location: Central Ohio
Posts: 48
Car: 1988 IROC
Engine: LB9
Transmission: Auto
1988 dual cooling fan operation once more

I imagine this has been posted and answered a zillion times but I cant find it via search. I am trying to figure out if my fans are operating properly or not with the A/C on. I have the GM manual and it gives proper operation sequences for each and every engine and cooling combination except mine, grrr. Car is 88 IROC LB9 with two fans. With A/C off the left fan cycles when it is needed and turns off when not needed. the RH fan never runs as it has never been hot enough to trip the sensor. (it does run if I jumper the wires at the plug at the cylinder head) which all seems normal? However If I turn the A/C on with cold engine neither fan runs until the high side reaches ( I think, I didn't write it down) ) 230 PSI and then both fans turn on until it drops to about 200 PSI and they turn off.

Two questions.
A- Guy who worked on my A/C is thinking that the RH fan should run continuously but he may have his models confused? I see in the manual that certain engines with one fan run it all the time when the A/C is turned on.
B- Also the wiring diagram for dual fans looks to me like only the RH fan should activate via the pressure switch? I am far from the best at reading electrical diagrams but the wiring harnesses show no signs of tampering.

One last question, car is black with T-tops. Just converted over to R135 with all new parts except evaporator. Gauge readings are normal according to the tech. Temps yesterday were low 90s and it struggled to cool the car, after sitting in the sun and getting real hot inside. That sound normal? Seems to me that years ago they would freeze you out of te car if you left them on max?

Thanks in advance!!
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Old 06-18-2018, 01:38 PM
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Location: Portland, OR
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Car: 86 Imponte Ruiner 450 GT
Engine: Various
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: 1988 dual cooling fan operation once more

R134 isn't as efficient in an R12 system. The capacities and sizing of the components is less than ideal so no R12 system will cool as well with R134. It will work - it's not going to blow 35 degree air like the old R12 system will. It will probably be 50ish degree air. Which is better than nothing and for many people it's the only option. There are R12 replacements that are closer than 134 and may cool better but they are more expensive and typically have other drawbacks like flammability, more prone to leaks, etc.

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Old 06-20-2018, 06:08 PM
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Car: 91 Trans Am Convertible
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Transmission: 5 SPD
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Re: 1988 dual cooling fan operation once more

Your "guy" is correct in that single fan systems will run the fan continually if the AC is on. One fan on a dual fan set up will also remain on. It is the driver's side fan and is tied in to the AC pressure switch, I believe. Hope this helps you.
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Old 06-21-2018, 11:44 AM
Join Date: Sep 2017
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Re: 1988 dual cooling fan operation once more

R134a has not ever and will never be able to cool anywhere near as well as R12. At best, it will cool the car maybe 20ish degrees less than the ambient temperature and that's if everything in that system is running correctly. The EPA screwed us as it was never as bad as it was said to be for the environment and now nobodys cars cool as well as they used to and we have to recharge our systems a lot more often than we used to. Sorry for the quick soap box stand. And, yes, as tavert said, your "guy" is correct about fan operation.

Sorry, not trying to steal this thread, but just a quick question. If I just took the AC out of my car, is it worth it to keep the second fan or should I figure out how to jump it to come on when the main fan comes on? I'll do searches for how to do that if everyone thinks I should keep the second fan and tie it to the main fan.
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Old 06-21-2018, 04:46 PM
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Location: Houson
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Car: 86 Firebird
Engine: 305 SBC
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Re: 1988 dual cooling fan operation once more

I would wire it to a second temp switch or a manual switch, with a relay. Or you can wire it with a separate relay to the same temp switch which would turn them both on at once. Do not wire them both to the same relay as it will over load the circuit. The temp switch just grounds the relay which causes the relay to close activating the fan circuit. You can ground both relays to the temp switch causing the fans to come on at the same time,or add a second higher temp switch to switch fan 2 on at a higher temp, or use a manual rocker switch to activate the second fan relay. Any of those will work, I personally would use a separate circuit with a second temp switch that way you would not forget to turn it off and it would act as a back up to #1 fan should it fail.

Last edited by mmadden55; 06-21-2018 at 04:50 PM.
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Old 06-21-2018, 04:52 PM
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Car: 86 Firebird
Engine: 305 SBC
Transmission: 700 R4 TCI
Axle/Gears: 3.42
Re: 1988 dual cooling fan operation once more

My 86 has a single factory fan but I added a second pusher aftermarket fan in front of the radiator on a separate circuit with relay and temp switch.
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