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LS1 PCM controlled Fans with Vintage Air Trinary Switch
OK I've searched around quite a bit on here trying to find my situation addressed without much luck, so I'll post it up.
Background:
LS1 in a 64 Chevelle, PCM controls Ford Contour/Windstar Fans using this basic wiring schematic:
Just finished up the Vintage Air install, and I have the trinary switch ground signal spliced into the #2 fan trigger from the PCM, with a diode added to prevent a uncommanded ground signal code.
So when AC is on, #2 Fan is running. However, according to my AC expert,
I'm not getting the airflow I need, so the AC system pressures are too high.
My question is, what are my options?
One would be to just "jumper" my relays, so both fans come on at once all the time, even when AC is off, but that doesn't seem ideal.
Could I splice in the Trinary trigger to the Fan #1 PCM trigger, and add several more diodes to keep backflow from occurring when AC is off?
You can splice your trinary switch wire into both fan trigger wires so they BOTH come on when A/C is on. If you have specific pressure numbers I would watch this video and see if they are in the specified range that Vintage Air recommends. This video is on Vintage Air's website. Vintage Air Install Video
Yes! seems like you could splice with another diode the trinity's ground trigger switch to the 2nd fan relay. I'd try that before getting too crazy in engineering any other solution.
I use a single 16" SPAL fan (2000-ish CFM if I remember correctly) triggered by PCM and by trinary switch for my vintage air setup and cooling the engine. I've not seen above 215F in high ambient (maybe 100F) and high humidity and idling with the AC on and blowing cool.
Here is a quick schematic I made up, relays removed for simplicity.
I think I would need 4 diodes as depicted to prevent a single PCM fan signal from turning on all fans.
There may be a simpler way to do this; maybe a 3rd fan relay? It's not jumping out at me though......
**Doug, to clarify, coolant temps are fine. Once one fan kicks on, it keeps temps at or below 185, it's the airflow across the condenser that apparently isn't adequate (I think).
I wired mine a little differently to not use diodes .... I use two relays, each able to independently power the fan. 1. The trinary switched relay and 2. the PCM switched relay each energize the 12V+ side of the fan and join the 12V+ relay outputs at a busbar. So, I use two separate relays to trigger the fan. At times, both might be on, which doesn't change that the fan runs.
Yours would be more complicated as you'd need to wire 4 relays and 2 separate bus bars (or isolated studs) for each 12V input to the fans.
Hope this doesn't seem to complicate your decision making, just wanted to point out there is another way without using diodes.
The trinary switch from vintage air should only kick on when A/C is activated. It doesn't ground out/trigger your fan relay unless A/C is commanded on in their system.
So with your car running now if your secondary fan comes on right away (low ECT temps) and with AIR OFF then you have an issue.
I wired mine a little differently to not use diodes .... I use two relays, each able to independently power the fan. 1. The trinary switched relay and 2. the PCM switched relay each energize the 12V+ side of the fan and join the 12V+ relay outputs at a busbar. So, I use two separate relays to trigger the fan. At times, both might be on, which doesn't change that the fan runs.
Yours would be more complicated as you'd need to wire 4 relays and 2 separate bus bars (or isolated studs) for each 12V input to the fans.
Hope this doesn't seem to complicate your decision making, just wanted to point out there is another way without using diodes.
Doug
Doug,
I am I'm a similar situation. Could you mock up a diagram for 4 relays? Much appreciated brother.
Hi,
I found this schematic someone else drew up online, but think you can follow it. The red circle would be the bus bar in my setup combining 12V+ from relays for the fan #2 controlled by either from the trinary switch or the PCM. I don't think you need to drive both fans when the AC pressures are high (pressure closes one side of the Trinary switch), so energizing one fan to turn on will get rid of the heat from the AC condenser.
Yes! seems like you could splice with another diode the trinity's ground trigger switch to the 2nd fan relay. I'd try that before getting too crazy in engineering any other solution.
I use a single 16" SPAL fan (2000-ish CFM if I remember correctly) triggered by PCM and by trinary switch for my vintage air setup and cooling the engine. I've not seen above 215F in high ambient (maybe 100F) and high humidity and idling with the AC on and blowing cool.
09-09-2016, 09:17 AM
LS1 PCM controlled Fans with Vintage Air Trinary Switch 
