Gen IV & Vintage Air

[MDPotter]

I've been thinking about this setup on my dad's 64 for a few weeks am not convinced it's right or maybe I just don't understand it. It's a Gen IV 5.3 with a Dewitts radiator/dual Spal fan setup. The radiator/fan setup came with relays and a harness and we used the trigger wires from the PCM to control them and my understanding is that the PCM turns on the first fan when the coolant reaches somewhere around 210 and the second comes on when it hits 230 or so. I don't know if these fans have a low/high function or not, they've only ran at what seems to be full blast.

We took the truck to a local shop to have them charge the Vintage Air system as they have experience with them. We had previously installed the trinary switch, but the shop told us we need to install a 3rd relay to control the fan so it comes on whenever the compressor is engaged. The other day, it was in the 70s and sitting idling, the compressor would engage for a few seconds at a time, so the fan was cycling every few seconds. Is that the correct operation? It just seems like the fan is going to get worn out with that much cycling and at this point I don't even know what the trinary switch does.

[sprint_9]

That doesnt sound right.

I posted some info in this thread : http://67-72chevytrucks.com/vboard/s...d.php?t=776599

As far as I know that info is correct, but I have not tested it myself yet. I can confirm that within HPtuners there is a table for AC system pressures and fan set points. I am hoping that the switch talked about in the above post relays that info to the ECM and it runs the fans according to the pressure relayed by that switch.

[Clyde65]

I’m not sure but I believe the gen IV compressors are different and don’t work the best, the Gen III is what I run with my Old Air Products AC.

I run a trinary and have the pcm turn on the one fan at 190, then the other at 210 or when AC is turned on. Hope this helps.

[First c10]

I think a trinary switch gives you 12+ when calling for fans so you will need a relay for a negative trigger for the cooling fans. Is this correct?

I think even with a trinary switch, the fans cycle when the ac compressor is engaged as soon as the pressure gets to the trinary fan set point and when it drops the fans turn off.

[ls1nova71]

A trinary switch is just that, a switch. Whether it provides power or ground depends on how its wired up. If you put power to one side of it, then when it turns on it will supply power, same goes for if you put one side to ground then the other side will be grounded when closed.