the dc controller hookes to both fans with one wire. just wire the fans together and run one wire to the controller. when the a/c comes one it goes to 50% and runs till the compressor goes off. when the engine heats up they come on at 10% and work there way up to where the temps go down.when i had my two fan set up they never came on more than 50% to keep the truck cool in houston traffic.thus keeping the voltage spikes to none and saving the alternater and electrical system. i just didnt like the dual fan mounts but have gotten to like the mad fan idea. few more dollars saved and ill order it. i believe that a lot of the lightning guys are running the dc controller as well.

 

i paid 18 bucks for my hayden fan controller from autoparts store... its holding up fine.

 

I've been told that all relays in cars with computers should have protection diodes on them, somewhere I probably have a circuit diagram showing where such diodes should be placed, but I can't put my hands on it now.

The surge induced, as I understand it, isn't from the fan motor, but from the current multiplying effect of the coil of the relay.

As for both fans running with the A/C, that is how it should be. Otherwise the A/C's not really running as it should, remember especially at idle the compressor's not turning at the speed it ought to, so the fans help compensate.

As for the worry about excessive drain on the alternator, don't forget you're actually freeing up a little hp that will allow the alternator to run a little more freely (since you're not cranking a mechanical fan now) and the most important thing to remember - your fans no longer turn 100% of the time any more. When you're running at highway speeds, provided your grille isn't impeded, your fans probably don't need to run at all, the natural airflow is more than enough. If you ran a pilot light from the fans into the cab, you could watch to see when they're coming on to verify this.

 

[QUOTE=pjb999@yahoo.co]I've been told that all relays in cars with computers should have protection diodes on them, somewhere I probably have a circuit diagram showing where such diodes should be placed, but I can't put my hands on it now.[//quote]

Please share. I'd love to read more about this. I've never heard of a protection diode and would be curious why all the rest of the relays on a vehicle aren't equipped with them.

Please elaborate on the current multiplying effect?


The fans do not help compensate for anything at idle except for the lack of airflow without a mechanical fan. In order for the AC to radiate the heat through the condenser, air must pass over it. With no mechanical fan, there is no airflow when the vehicle is stopped. The electric fans need to move air across the condenser to dissipate the heat that the system carries out of the passenger compartment. The fans running with the AC have nothing to do with the compressor speed at idle.

Agreed, however the electric fan does not allow the alternator to 'run more freely' as you put it. There is an extra drain on the charging system only when the fans are running. However, the alternator can easily handle the extra load in all but the most demanding circumstances. Keep in mind it's only a 30A draw max. The blower motor alone will draw near 30A on high by itself.



Mark05KR, why wouldn't you want both fans to com on with the AC compressor? You want maximum airflow across the condenser for maximum cooling, don't you?


-Joe

 

Hi.

Two separate things going on here....

First: in any DC switched/inductive application where a solid state device is used to control a relay, yes, a diode needs to be present across the relay coil to protect the solid state device from 'back-emf' - the reverse polarity pulse that is generated from the relay coil when it de-energizes.

Second: as indicated previously, another type of suppression (to reduce arcing across the relay contacts) should also be present to ensure long contact life - again, in a DC switched/inductive application.

Now, if you are using the controller with a relay already present, then assuming the controller already has the diode protection built-in ( it had better!), you can use that relay's contacts to switch a higher power external relay to run the actual fan load, as I indicated ealier. No additional diode across this external coil is required, but a suppression network across it's contacts is still a good idea.

Relay contacts don't need diode protection - they are not harmed by 'back-emf', but a solid state switch does.

The diode can be a standard silicon 1N400x unit - 1 amp, 100-400 v PIV.

Hope this helps.

Cheers
Bubba

 

Thanks Bubba. Care to mention how the diode's connected? Might be good for the record. I've forgotten, it's been so long, and the paperwork where I may have kept it is either still at the ex-wife's house, or in my stuff in storage in Vancouver, waiting to clear customs (I moved back to Canada from Oz.)

 

I installed dual 16" with dual thermos works great wait till you get the smile when you let off the gas at 60 or so just keeps humming anyway junes had the best price when i shopped months ago go to jegs or summitt they have all the mfgs for fans

 

I just don't like the way the A/C compressor cycles whenever the climate control is on. The climate control system seems to always use the A/C, summer and winter. I can hear the compressor engage and disengage every couple of minutes. It doesn't stay on very long. It doesn't seem like it would be a good thing for the fans to be turned on and off for that short of a period of time that often.

I always have the climate control on, so the fan(s) would constantly be turning on and off.

I broke down and replaced my broken controller with the 'new and improved' Troyer controller, just because of the price. I did not connect the controller to the A/C compressor. I am going to get in contact with Troyer and find out how to wire a manual switch to the A/C compressor lead. That way, if I am running the A/C in the summer in stop and go traffic, I can turn on the fan manually and it will not come on in the winter or when I am moving down the road.