View Full Version : Mod that keeps the cooling fans on when the AC is on ***Split***
I can't find the documentation on the mod that keeps the cooling fans on when the AC is on, regardless of the compressor being on, or where the mode with set to. It is somewhere out there.....
That is the way it is already wired from the factory. Sounds like the Cooling Fan Breaker might be tripping (40Amp. Maybe it's weak, high fan amp draw, ??)
Ron,
I am not so sure about this. I found the post by Darryl from the old list. Perhaps the early models did not have this feature and it was corrected later.
Here is the post:
Author/source: Darryl Tinnerstedt/McElraft
To prevent the cooling fans from cycling with the A/C compressor (i.e. they are on any time the A/C is on, regardless of the compressor cycle) do the following modification.
Locate the tubular diodes in the large wiring loom just inboard of the fuse box. Locate the pink wire and disconnect it from the diode. On a length of 16 gauge wire install an appropriate blade connector and plug it into the diode where the pink wire was. Route this wire under the console by tucking it under the console and pulling up on both ends. The other end of the wire should be up on the floor hump under the dashboard on the passenger side near where the wires from the A/C mode switch go to the pressure switch on the A/C accumulator behind the right front tire. Disconnect the pressure switch plug, and with the ignition switch ON and the mode switch in A/C use a test light to find the pink/orange wire leading to the pressure switch that is "Hot". Turn off the ignition and using a parallel wire splice (3M Scotchlok) connect the new wire to this hot lead. Reconnect the pressure switch and test the system.
The cooling fans should now run any time the mode switch is in A/C, regardless of whether the compressor is cycling on and off or not.
Original by Darryl Tinnerstedt/McElraft
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David T
07-05-2019, 03:00 PM
That is the way it is already wired from the factory. Sounds like the Cooling Fan Breaker might be tripping (40Amp. Maybe it's weak, high fan amp draw, ??)
Make sure what is clicking, the relay or the cooling fan circuit breaker. The breaker usually won't click that fast. Check that you have the uprated (40A) circuit breaker. The relay should be clicking but 3-4 seconds is too fast and means you need some refrigerant or the low pressure switch needs to be adjusted.
David,
I don't really have a problem with cycling or clicking. I was just perturbed that when it does cycle, the cooling fans at the radiator go off. I remembered that there was a modification for this. But Ron says it is wired that way from the factory. So, I and trying to sort that out.
Ron,
I am not so sure about this...
I'm so sorry Steve!!! I missed where you said, "regardless of the compressor being on," somehow.
I assume the mod you found works. Hope this helps you follow it and/or make it easier to do:
60546
Thanks Ron.
So, from the factory the radiator cooling fans will cycle with the compressor, correct?
I have not done the mod yet. I was thinking that an easier way to do this was to key the radiator fan relay with the +12 from the high setting of the AC fan (I always have it on the highest setting). Gee, that connection is right there a few inches away! Just a thought.
Yes, as long as the Otterstat doesn't override and turn them on...
If you mean as in the below, I think it would do as you say, but it would also make the fans run when the Heater was on and at 4th speed.
The diodes (circled) should prevent interference with other circuits.
(Maybe add a "summer/winter" switch in series with the jumper ;-)
60547
There is always a "but", eh?:)
David T
07-05-2019, 09:06 PM
The stock (original) mode of operations of the fans is;
1) the "O" switch controls the fans on and off when the ignition is on
2) When the A/C compressor clutch engages the A/C overrides the "O" switch and causes the fans to run regardless of what the "O" switch wants.
The way the electrical system is set up the fans and the A/C MUST cycle. If you set up the A/C or the fans to run continuously you will overload the electrical system.
+1 on a stock system.
$.02:
3) When the "O" switch engages, it overrides the A/C and causes the fans to run, regardless of what the A/C switch wants.
$.04:
A D with one of the "high amp" (90+) aftermarket alternators (and the correct size pulley...) would keep up with the fans always on, and then some.
$64.00?:
What's an "O" switch? It sounds like something that 'Oughta be jumpered' for the hot summer months!! :devil:
Since you were considering jumping the relays and having the fan run when it's on 4th speed (always for you...), consider using a fuse to jump the Otterstat -- The fans would run whenever the ignition was on, but it's non-intrusive, Plug-N-Play...
DMC-81
07-06-2019, 04:32 AM
If the problem statement is "prevent the cooling fans from cycling with the A/C compressor (i.e. they are on any time the A/C is on, regardless of the compressor cycle)"' another plug and play alternative is the Solid State Fan Relay from Dave McKeen. From his website it "Delays fans for one second and keeps fan running for 20 seconds minimum. That eliminates fans cycling when AC cycles. Plug and Play."
I have that unit and his Solid State Fan Fail unit. These 2 parts are a great upgrade, as are his other offerings.
That would do the trick...and no "buts"! :)
why do you want to do this?
Seems like you have cooling system problems you are trying to mask
DMCMW Dave
07-08-2019, 12:57 PM
The way the electrical system is set up the fans and the A/C MUST cycle. If you set up the A/C or the fans to run continuously you will overload the electrical system.
I wired my personal car like this in about 1998, actually using Darryl's instruction. Still no overloads, no melted wiring, etc. I do maintain the connections. I was likewise tired of feeling the fans come on and off with the compressor. My car has aftermarket high power fans (not the modern low-current ones, but from another European car circa 1995). I see no detriment. Having the fans cycle on and off doesn't really prevent any overloads, in fact a constant current rather than repeating the startup current over and over seems beneficial. My own observations, YMMV.
Is there anyway to prevent the fans from coming on when AC is on?
Bitsyncmaster
08-19-2019, 07:54 AM
Is there anyway to prevent the fans from coming on when AC is on?
Pull the diode that has the pink wire on it. No fans when the AC is on will probably blow an AC hose.
Pull the diode that has the pink wire on it. No fans when the AC is on will probably blow an AC hose.
Why would it blow a hose?
FABombjoy
08-19-2019, 09:10 AM
Not all cars have a high pressure cutoff switch or relief valve.
If you have a car with no HP switch (and consequently no high pressure relief valve), and the compressor never shuts off, and the condenser can't eliminate enough heat for the low side to function properly, all that energy has to go somewhere.
Bitsyncmaster
08-19-2019, 11:29 AM
Not all cars have a high pressure cutoff switch or relief valve.
If you have a car with no HP switch (and consequently no high pressure relief valve), and the compressor never shuts off, and the condenser can't eliminate enough heat for the low side to function properly, all that energy has to go somewhere.
+1
With no fans running and the AC on the high pressure goes really high.
David T
08-19-2019, 11:52 AM
Not running the fans would work but only if you are moving fast enough and even then it might not be enough. You must still have things set up so if the motor got hot enough it would turn the fans on. If you don't run the fans with the A/C you take a big chance of overheating the motor. Why would you not want to run the fans with the A/C?
Why would you not want to run the fans with the A/C?
Driving at highway speeds with a car that has an aux fan switch.
FABombjoy
08-19-2019, 02:48 PM
I tried VSS-based fan shutdown and reverted to stock operation after a weekend, and that's with an aluminum radiator.
I found it doesn't seem to take much to disturb the airflow through radiator and temps will go up fairly quickly. Maybe at 70MPH+ it would be OK. I was driving behind a large truck at about 45 and temps went up to 217F before I turned off the AC to cool things back down.
I tried VSS-based fan shutdown and reverted to stock operation after a weekend, and that's with an aluminum radiator.
I found it doesn't seem to take much to disturb the airflow through radiator and temps will go up fairly quickly. Maybe at 70MPH+ it would be OK. I was driving behind a large truck at about 45 and temps went up to 217F before I turned off the AC to cool things back down.
Interesting. Thank you.
Driving at highway speeds with a car that has an aux fan switch.
Aux cooling fan or AC fan, switch?
When the clutch cycles off, the Otterstat will keep the cooling fans on if the engine temp is above normal temp anyway. So I don't understand what you are after either...
hippieman9
08-21-2019, 01:56 AM
I can't find the documentation on the mod that keeps the cooling fans on when the AC is on, regardless of the compressor being on, or where the mode with set to. It is somewhere out there.....
Dave Mckeen sells a Fan relay that keeps the cooling fans on while the AC compressor cycles. I have it in my car and love it. takes the load off the electrical system.
Aux cooling fan or AC fan, switch?
When the clutch cycles off, the Otterstat will keep the cooling fans on if the engine temp is above normal temp anyway. So I don't understand what you are after either...
I have an aux radiator fan switch.
What I was wondering, basically, was “why do I need the radiator fans on when my AC is on?”
I have an aux radiator fan switch.
If the switch was already installed, my guess would be that a PO installed it as a backup since the electrical system leaves a lot to be desired. It worsens with age, and often blamed when neglect was the problem. Unless there is a problem with the OEM setup, the switch isn't going to help much, if any. ("Giving it a head start" only matters for a very short time....)
What I was wondering, basically, was “why do I need the radiator fans on when my AC is on?”
Because the fans blow through the radiator AND the condenser (a radiator for the AC system).
When Freon is compressed, it gets very hot. It is piped to the condenser which transfers the heat into the open air (just like the radiator does with heat in antifreeze).
Because the fans blow through the radiator AND the condenser (a radiator for the AC system).
When Freon is compressed, it gets very hot. It is piped to the condenser which transfers the heat into the open air (just like the radiator does with heat in antifreeze).
I understand. But the radiator doesn’t need help at speed. Apparently the condenser does. That’s all I need to know.
The condenser's input temps can get near 200F. And it will radiate heat to the already "hot" radiator, since they are almost touching, making them both need the fans. Not to mention the hot air (from highway speeds) flowing through one then the other...
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