I went to have the AC charged, and they said, "NO can do" until you get your fans to come on with the AC clutch. So, being a well documented, and proven electronic moron, but very willing to give anything a try, I tried splicing the clutch signal wire over to the fan thermostat that activates the clutch. Guess what, when the fan comes on, the AC clutch does too. So, I am thinking I need to redesign things here.

Currently the fan relays switch the 12+ side to the fans, and I am thinking that if I switch the ground side instead of the 12+ , not only can I eliminate at least 4 wires, this will eliminate the feedback that is turning on the clutch when the fan relays are triggered. Then, in addition to that, I was going to install a seperate relay triggered by the fan clutch signal wire that also connects the ground side of the fan circuit.

I tried going on line to Vintage Air's web site, which I know has fan wiring instructions, but their web site was not responding. So, I turned to the brightest group of guys I know here on the /6 forum. Any ideas there? Am I barking up the wrong polarity here? Thanks.

Sam

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If you put a diode in the wire that goes from the AC clutch to the fan relay. That way the current can only flow one way. When the AC clutch is activated current will flow to the fan relay, but when the fan relay is activated current cannot back-feed to the AC clutch. Just about any 1 amp or larger rectifier diode will do.

1 amp diode at Radio Shack.

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Joshua

install a diode in the A/C clutch wire to the fan relay. That will allow the power to flow from the clutch to the fan relay, but not back to the clutch, when the fans come on due to engine temp.

Personally I would install a pressure switch in the A/C hich pressure line, that will turn the fans on at approx 200 PSI. That way when going down the road, with enough air flow, the fans will not run.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

You're close, just need to add a diode.............


There's a couple of ways that thermostats (negative side or positive side of relays).

So describe how it's wired without the A/C, then we can figure it out.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The thermostat is just a switch that is normally open. It is adjustable to close at any temperture. When the switch gets hot enough, it closes and sends 12+ to an relay, which closes and sends 12+ to the fans.

I was thinking that if I ran the 12+ to the fans unbroken, I could switch the ground, and thus turn the fans on and off with just a ground being completed. It is my understanding that the injectors work this way, no?

If I make and break the ground, then turning the fans on, will not effect or feed back to the AC clutch. Then, to get the AC clutch to start the fans, have the same wire that closes the clutch relay when the fan is turned on, also close another seperate relay which will close the ground to the fans. Does that make sense? This would eliminate the 12+ wires that go from the thermostat to the relays, and the 12+ that goes from the relays to the fan. The same wire tht provides the 12+ for the thermostatic switch could also supply the 12+ to the fan. That is at least two wires gone, and there are two fans.

In any event, the relay box that is currently in use for both fans, and headlights is an old junk yard piece from a Chevy Geo. It needs to go, and be replaced with better stuff. It looks bad, the wires are old, and there is much left unused in the box as well. No matter how I wire it, there will be new parts in there. I know this sounds redundant, but the discussion earlier involving wiring was the other fender, and other problems which are now solved. Thanks for the advice.

Sam

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Sounds like you are trying to do things the hard way. With the pressure switch, I recommended, just wire the pressure sw in parrallel with the fan thermostat. Done deal.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Ok, the thermostat sends power thru it. (some thermostats just ground out, so they're on the ground side of the relay).

You're best bet is the diode mentioned by everyone. Don't need another relay that way..

I also like relaying the power side. There's no power to the device when it's off (the fan wires will be hot even if the fan is off when the switch is after the fan).

There's also less wire laying around that has power when things are off. (The wires to the fan, from the fan, running back at forth will have power in them.)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Thanks guys. Vintage Air's web site finally worked, and they idicate switching the hot side of the fan, just as Ems says. Their system also supplies the ground to the relay, which seems like a good way to go as well. I am going to put the fan relays nearer the fans to cut down on much of the wire.

Charlie, it seems as if a pressure switch involves openning the the AC refrigerant lines. Would I have to drain the sytem? I don;t have the equipment to capture the refrigerant, so would have to have my AC guy do it. I guess that would be OK.

Not only am I an electrical dummy here, but it seems an AC dummy as well.Do you mind giving me a short background fact that will help me understand where this pressure switch goes, and how and why it works, and or is needed. ? There is such a switch and associated wiring included in Vintage Air's web site instructions. Your comments and the downloadable instructions will dovetail. Thanks very much. I do not take this help for granted.

So here is the really basic, Dumb-dumb question: If pin 30 and 85 both are wired for a 12+ switched voltage, is there any reason you cannot simply jumper the two together. I am going to create some kind of unexpected feed back monster here? It seems as if jumping them together would be the same as running a seperate wire out to the same source.

Sam

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Maybe yes, and maybe no, it depends on your setup.
If you want to call me, I can ask you some questions, and advise you. I will pm my phone number. I was under the impression you didn't charge the system, yet. When the A/C is off the high side pressure, will be below 100 PSI. As the A/C runs, the high side temp/pressure rises (without fans, the pressure can go over 400 psi). The Ideal pressure is about 175 to 275 PSI, with a max of about 375 psi. The job of the condenser is just like a radiator (to remove heat and therefore lower the pressure). The fans supply the air flow to do this. As the vehicle goes down the road, the ram air is usually enough to do the job, without needing the fans running. Whenever I do a a/c install, or retrofit, I use a low pressure safety switch, to protect the system, in case of a leak. A high pressure fan switch to control the fans, and a high side safety to protect the system, in case the fans fail, or there is a high side obstruction. The switches can come in different configurations. three singel switches, a binary switch, that combines two functions, in one switch, or a trianary switch, with has all three functions in one switch.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Thanks again Charlie. Vintage Air has a trinary switch for sale, and a set of instructions on line. I downloaded the instructions. It wires in conjunction with the relays I just installed, which work fine, so can be added later if I want. I may give you a call to chat sometime soon. Thanks again.

Sam

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