I have been running my Taurus fan for about a year now with no problems... well today I start the car and am going for a cruz... well I notice the temperature start rising... 180-190-200 210... I pull over... no fan... so I check the relay (My Gen VII controls the fan it is supposed to come on at 160) I turn around and luckily it was down hill ... well I am costing and I notice the temp keep going down... I get back home and the fan was working now??? WTF... So I go back out and by the time I am back 1/2 across town I notice the damn temp is rising again!...

Long story short... It was my bosch 75 amp relay... so I had to hard wire the fan to power and ground (on the side of the road!!) So here is my question..

1. I got back home and had two 40 amp relays... here is how I hooked them up... 2 10 gauge wires for 12v Power (one of each relay spliced into one 10 gauge wire to 12V), I ran ground from the gen VII (that is how it controls the fans), 12V key hot power (one wire spliced to both relays), and then I ran 2 wires (10 gauge) to the Taurus fan and connected all three of them together (so each wire is going to a different relay)..
Is this a bad way to wire a Taurus fan?.. I know they have a massive power spike on the initial start up... and is this considered running the relays in parrell?

2. I noticed the power wire that was going from the 75 amp bosch relay to the fan (it was just a male and female connection) was charred??.... it was charred where the fan connected with the wire from the relay... Why would this be?...

 

you have the two speed fan right? i just use the low speed wire, flows plenty.. but if you want

http://forums.hybridz.org/showthread.php?t=99700&highlight=taurus fan wiring

 

The way you have it wired up is in parallel and it will work that way, but it's not recommended. If one of the relays were to fail, you'd pull the max starting current through the single relay and then you have a fire hazard. I use a large winch relay/solenoid from Napa. Runs about $40 and works like a champ, even in hot S. Texas heat. The old part number is ST87, but any Napa should be able to cross-reference it over to the newer part #.

I run a SN-95 fan, but am looking and changing to a Mark VIII fan to try and keep temps down. My fan circuit is:

8ga wire from battery to 60A fuse holder.
8ga from fuse holder to one side of winch solenoid
8ga from other side of winch solenoid to High-Speed terminal on fan
8ga from ground terminal to good chassis ground

Solenoid is activated by a stanard 30A automotive relay in the car. That's controlled by the ECU. I have several friends who have been running this setup for 5+ years on the street without a single failure.

I have to ask - why did you change from the SN-95 fan that came in your car to the Taurus?

Good Luck!

 

I will check that relay out for sure!... I swapped the sn fan for a bunch of different setups (dual spal fans, black tragic fans, etc etc etc!) to find out it was my damn front mount intercooler the hole time... well by the time I found this out and went with a VS racing one (Very nice piece) I had sold all my setups...and I went to the junk yard and found one of theses and just decided to run it... It actually pulls more CFM than the Sn fans and like mentioned earlier it is a 2 speed fan (I only run the high speed though)

 

You can run the two parallel relays and as long as you individually fuse them it will prevent the hazard described above.

 

when you say individually fuse them you mean just add a inline fuse (say 25 amp)... what would that have anything to do with the relay going out?...

 

I was not refering to the root cause of your initial problem. I was refering to the post by red95gts and the potential fire hazard he described. You would put an inline fuse on each power wire feeding each relay. A fuse should be rated around 25% over the circuit's rating. This is because a fuse will blow at around 80% of its rating if that current is present continuously. This means with two fuses each one should be rated around 40% of the required current needed.

I guess I should try to help with your root cause. I suspect you are not running a freewheel diode and the burn marks are ark marks. Open the relay up and investigate its contacts. If my suspition is correct they are burned much worse than the external marks.

 

I heard about the freewheel Diode's but I was under the impression that the bosch 75 amp relay had them built in.... and now I have two different 40 amp relays so I really don't know if they have them or not.. If I am correct all the freewheel diode does is stop current after the fan has been shut down (stored current)...

 

I've seen relays with the diodes built in on the coil side but not the power side. The diode is to give the current a path to decay when the relay opens instead of arching across the contacts.

 

Gen VII can control 2 fans. Why don;t you use fan control #1, wire it to large relay to control the low speed (smaller initial spike than starting the fan from a stop to high speed) and then wire the fan control#2 to a smaller relay to high speed. The fan will be already spinning, so when high speed kicks in, there should not be as big of a draw as on start up.

I personally run Nissan fans which are dual fans/ dual speed. I have a 100 amp solenoid wired to fan control #1 hooked up to start both fans on low speed. Then a 40 amp relay wired to fan control#2 set up to both fans on high. Hope this helps

 

where did you find a 100 amp relay?... And I just use the high speed because I have to (damn mustangs and overheating) It would just be a matter of seconds between the temps to run the low and high...

 

It's not a relay it's a solenoid.
I understand the use of the high speed, but if you start it on low first and then (lets say 5 degrees later) turn on the high speed you lessen initial draw from a stop to high speed, which can be over 110 amps on some fans.
If your electrical system is up to par then you can leave it as it just use a solenoid instead of relay

mine looks like this

 

Do you have a part number on the starter solenoid you are using... And my electric system is up to par so I think the initial draw is ok... (200 Amp alternator, Duralast gold batter etc etc)

I was curious about wiring these up... I know I can find theses at a local radio shack... but where do they attach?... do the actually go between the +/- terminals of the fan?... and do you just splice them in? I don't think I have ever even seen one...

 

The Napa ST87 I mentioned above looks just like that, except that it only has one smaller terminal. Works great.

 

So you need a relay before this solenoid?... so Just run the relay and splice the 12V power source into this solenoid?... or does it go on the fan lead (86 accessories on the relay?) ...

 

You put it across the fan terminals and yes you can simply spice it in. The cathode side of the diode will have a line and this is the side you will hook to the positive of the fan. A diode can handle much more than its rating intermitantly so you don't need a diode rated for the full fan current for this application as it will only be used at turn of for a few mS. Seems like the write ups I've seen on the Mark VIII fans in the past have spelled all of this out pretty well.

 

Ok so I went and purchased the diode part # 1N5404 (radio Shack FTW!) ok so do I just solder them together?... And here is a quick pick of them... (just making sure I got the right ones) And I do see the line on one side... and you said that goes to the + side of the fan motor right? ...