84/85 Cars Running Dual Fans

[6SENSE]

Okay guys/gals, I got the Ramcharger's dual fans last week. Installed them and was impressed, except for one problem. They keep blowing 30amp fuses. They cant be drawing that much amperage!
I was running a stock '87 fan before so electrical hookup was pretty much a breeze, should have been plug and play.
Heres the lowdown:
Im running the trigger lead from the '87ECM out to the driver's side fender (near where the charcoal canister used to be) to a 30amp relay. PWR to the relay is 10GA coming from the battery with a fuse in line a few inches from the battery.Ground for the fans is 10GA to the frame near by. As soon as the ECM triggers the relay, the fan starts for a split second and then the fuse blows. The only thing saving me is that I had a manual switch wired seperately (no relay). It gets pwr from the fusebox (batt, not ign). When I pwr the fans this way there is no problem. I know the fuse in the fuse box for this circuit is less than 30amps, but it doesnt blow.
Am I missing something here?? Ive checked for shorts in the pwr wire with a VOM and even rewired it just for the heck of it. Ive tried different relays. Ive tried getting pwr differently, by borrowing my alky pump's relay pwr lead from the alternator, and yep the fans blew that fuse too.
This is something I cant leave hanging. I already forgot to turn on the fan once when I was driving yesterday (until I saw almost 200 degrees on the guage). Any help would be appreciated.

 

[Bat]

Without knowing the exact set up you have I can only give my .02cents. You may need to run split relays for the fans. Use everything you have and use two relays ( one for each fan). Together one relay may not be able to handle it all. A relay reduces the amount of power needed to run the fan but, now it has two to run and it maybe too much. I read some where that if you run duals you need dual relays one for each.

 

[6SENSE]

Thanks Bat, I didnt think of that.

These dual fans are definately pulling more pwr than the single. Tuesday night, 1st time at the track with them and my battery went dead in the pits from running the fans off and on (and starting and stopping the engine) using the maual switch. During the last 3 years or so, this never happened with the single.

Do you know if cars that come factory with dual fans use a relay for each fan?

 

[Bat]

I don't know but, I found the mag I read about the dual relays. Chevy High Performance ( May 03 ) pg. 68 pic #4 explains "Dual fans require the use of two relays". There is also a reference to a book buy Mark Hamilton of MAD Ent on Electric wiring www.madelectrical.com There's a lot of info there.

 

[6SENSE]

Thanks again. Thing is, the GN/TR adaptor plug that Ramcharger's gives for the fans has both pwr wires and both grd wires for the fans respectively wired together to use the one stock '87 plug. So, they are expecting the use of only one relay. It must be working as is because I havent heard a bunch of '86/'87 guys going crazy about there fans burning up their relays, fuses, etc.

I know there was at least one other Hotair guy on this board that I noticed had the RC fans, I cant remember who though. I was hoping he would chime in to share how he wired his up.

Im going to try wiring up my relay slightly different and see what happens. If I get the same outcome, I will be loooking into dual relays.

 

[Chad Oliver]

I'm one of those hotair guys

My setup consists of the RC fan and their adaptor. Caspers Electronics fan relay install kit. It uses about a 18-22 gauge power off the batt, no fuse. The ground is the same size.

The ecm wire goes across the back of the firewall from the driver's side to passenger fender. The 30 amp relay is setting inside the fender by the battery. Ground is to the fender by battery. The harness plugs into the fans at lower right (passenger side). HTH

 

[mweber]

The problem is the inrush current of two fan motors. The inrush current when the fans start is causing the fuse element to start to open and once the fans are turning the fuse element has increased in resistance so much that the fuse opens under the reduced current. You need a fuse with a higher I^2*t. I always use a Maxi-fuse on my fan setups it can withstand higher inrush current compared to an ATO fuse.

Sorry for the long explaination but thats what happens after designing fuses for 10 years.

Mike

 

[6SENSE]

Thanks guys. Am I just pushing it running the pwr wire from the battery over to the passenger side?

Bat, I found the dual fan article you mentioned at the Chevy High Performance website. The exact address for the "how to" article is www.chevyhiperformance.com/howto/4572/ . It mentioned a few things that caught my eye, such as "long lengths of heavy-gauge wire cause a substantial voltage drop; a shorter wire between the battery and the fan reduces this drop and improves performance." It talked about how the idea between relays is to run the largest amount of current to the load as possible, by using the shortest amount of heavy-gauge wire between the battery and the load.
Maybe Im not thinking about it correctly but if Im blowing 30amp fuses instantly there doesnt seem to be any voltage drop, but too much voltage . What would happen if I didnt use a fuse, and just ran straight to the battery??

I have never spent this much time wiring before. I cant believe it has been this tricky. I have taken less time on alarms, sound systems, and even wiring switches for hydraulic setups .
I went ahead and got one of those remote battery hookup boxes (w/ cable, etc.) that are used on most of the newer cars from the junkyard. Im going to run it over to the passenger side. If I wire pwr from this isnt it the same as hooking straight to the battery? So I can just keep my relays where they are and hookup a shorter pwr wire to this?