What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Inspect my fan circuit please

nutt7

nutt7

1/2 ton status
 Premium
Joined
Dec 30, 2010
Posts
839
Reaction score
471
Location
Ahwatukee, AZ -> JBLM, WA
Let me know what you think...

Background: windstar fans, intended for both to run together. I have an "on-off-on" switch (goodwill $0.99). I want to have it run "on-off-auto" from the switch. I have A/C and plan to run the fans whenever the A/C is on. I think it looks good except that I need to make sure my A/C is off if I get deep into water :rolleyes:. Please let me know if you see any faults or you feel the need to advise before I approach this. All questions and advice from your experience and expertise are welcome. :D

WindstarFanCircuit.jpg


PS this was made in Paintbrush on my mac. Know any good/easy/free circuit drawing programs?
 
You don't have to run the + through the switch, only the ground side. The way you have it you are just creating more wires to run. It'll work, just adding more failure points (places for the system to fail over time).

Are 30a relays big enough? Just curious...

I'd run ign power to the relays (not through the switch) and just switch the ground side.
ON, straight through the switch to ground.
OFF, open through the switch.
Auto, through the switch to the temp switch.

You can also delete the connecting power wire from a/c to the + side of the relays cause the relays will already have their ign + source. With a/c ON it will energize the ground circuit relay and turn the fans on.

Keep it simple. It will be easier to build and easier to diagnose in the event of a failure.
 
496truck said:
Are 30a relays big enough? Just curious...
Click to expand...

I couldn't find the current draw for these fans, but someone said he ran both off of a single 40A relay for 12 years, no prob. On mine, each fan has its own supply and a 30A relay so I assume it will be fine. I've seen others that claimed to use 30A relays and haven't heard anything negative. I have plenty of the 30A ones laying around, so I don't mind testing them out.

496truck said:
I'd run ign power to the relays (not through the switch) and just switch the ground side.

You can also delete the connecting power wire from a/c to the + side of the relays cause the relays will already have their ign + source. With a/c ON it will energize the ground circuit relay and turn the fans on.
Click to expand...

I changed my plan a couple times and failed to see these redundancies, thanks for pointing them out.

496truck said:
ON, straight through the switch to ground.
OFF, open through the switch.
Auto, through the switch to the temp switch.
Click to expand...

How about this one?:

WindstarFanCircuit2.jpg
 
The 3rd relay is only required because you are switching ground on the coil/logic side. If the temp switch was tied to 12V, you could use a couple of small diodes instead. But I suppose it might be the kind you screw into the block with just a single terminal on it.

Since you already have a DPDT switch, you could route the "A/C" line from behind the HVAC controls through the second pole. This would disable your compressor when you switch the fans to off. You don't want it running without fans, as you will quickly either trip the high pressure cutout switch (if you have one) or the blow-off valve and vent refrigerant.
 
Blue85 said:
The 3rd relay is only required because you are switching ground on the coil/logic side. If the temp switch was tied to 12V, you could use a couple of small diodes instead. But I suppose it might be the kind you screw into the block with just a single terminal on it.
Click to expand...

It is the screw in, self grounding type.

Blue85 said:
Since you already have a DPDT switch, you could route the "A/C" line from behind the HVAC controls through the second pole. This would disable your compressor when you switch the fans to off. You don't want it running without fans, as you will quickly either trip the high pressure cutout switch (if you have one) or the blow-off valve and vent refrigerant.
Click to expand...

That is something to think about...but I would need another relay, unless you think my 20 or 25A switch can continuously handle the compressor actuating load (anyone? compressor current draw?). I doubt my A/C would ever be on when I need to override the fans to OFF and I'd like to think I will remember to turn the A/C off too :D , but who knows. Here is what the circuit looks like with the advised compressor control:

WindstarFanCircuit3-1.jpg
 
nutt7 said:
That is something to think about...but I would need another relay, unless you think my 20 or 25A switch can continuously handle the compressor actuating load (anyone? compressor current draw?).
Click to expand...

Well since you asked... I recommend adding another relay to take the load off the low-side pressure switch. Then you can just swap relays after a few years instead of swapping pressure switches. Even a pressure switch that's too pitted to pull the clutch in will still close a relay. This would give you the option to switch the low-side of the clutch instead of the high-side and use that as a signal for the fan relays you posted above. You just need some diodes instead of the 3rd relay you show (still 3 relays total). Or you may want to keep the A/C wiring closer to stock to "go back" if you want or bypass in case of trouble.
 
I'm not following...I understand that I can run the A/C "on" wire that goes to the pressure switch (you are talking about the one on the accumulator, right?) through my switch and from the switch to 85 or 86 on a relay, then I need a new +12 source to run to the relay and finally to the compressor...is that what you mean? I would still need a negative signal for my fan relay, thus another relay. What would I need the diodes for and where would they go?

Am I misunderstanding?

Thanks
 
I am thinking of not worrying about that switch. If its the one on the accumulator, it cycles the a/c on and off to prevent icing over the evaporator. Mine is currently bad and I have a jumper wire on the connector. It's too hot and dry to ice over here anyway. When I install my new condenser, I will replace the switch and add dielectric grease to prolong its life.

Happy 4th! Good to be free! Thanks to those who defend it!:D
 
The low pressure switch is a normal part of the A/C operation. Sure, under some conditions the compressor is always on, but that's not really the right way to do things. I had a stuck switch once keep the compressor on and eventually the whole air box filled with ice and there was no longer any airflow coming out of the dash. The more frost you get on the coil the worse it is at transferring the heat out of the air. Plus it's a waste of gasoline.
 
Blue85 said:
The low pressure switch is a normal part of the A/C operation. Sure, under some conditions the compressor is always on, but that's not really the right way to do things. I had a stuck switch once keep the compressor on and eventually the whole air box filled with ice and there was no longer any airflow coming out of the dash. The more frost you get on the coil the worse it is at transferring the heat out of the air. Plus it's a waste of gasoline.
Click to expand...

I know...it's getting replaced. It happened right after a new compressor install...wasn't about to shell out the cost of an evac and recharge again.
 
Blue85 said:
The low pressure switch is a normal part of the A/C operation. Sure, under some conditions the compressor is always on, but that's not really the right way to do things. I had a stuck switch once keep the compressor on and eventually the whole air box filled with ice and there was no longer any airflow coming out of the dash. The more frost you get on the coil the worse it is at transferring the heat out of the air. Plus it's a waste of gasoline.
Click to expand...


If you iced up, there is something else wrong.
 
British Slave said:
Low pressure switch can be replaced without loss of refridgerant.


The point I'm trying to make, why add another relay and wiring if it's not needed. Just more possible cases of trouble.
Click to expand...

I've decided against the relay, I was trying to hear out blue85. It seems more hassle than its worth.

We keep talking about the "low pressure switch", are we talking about the switch on the accumulator? (some call it a compressor cycle switch) :dunno: Is it on a schrader valve or something? I thought you had to open the system to replace it.
 
You must log in or register to reply here.

Latest Posts

Top Bottom