RC Dual Fan Amp Draw Test

O

OKTurbo

Member
Joined
May 28, 2001
Thought I'd share some info....

I have the Ramcharger dual fan set-up on my 87 GN using the RC harness.

At the prompting of another tb.com member, I checked the harness wires while the fans were running. Just like the other member....the wires and harness on my fan were VERY hot.

So, I figured that I would rig up a separate relay to "hot wire" the dual fans. Hopefully this will save my original wiring from burning up.

What I have now is a 10ga wire straight from the back of the alternator through a 30A fuse (to the relay then) to the fans. The fan ground is 10ga from the fan connector to a bolt on the driver's inner fender (already two factory grounds there).

The factory wiring now triggers the relay. I was able to cut up the RC harness so I didn't have to butcher the factory harness....plus used the other connector for the fan.

Hooked it up....and flipped the manual fan switch....click...pop...blew the 30A fuse. Hmmmm....checked everything out. Nothing wrong. Replaced fuse and tried again....POP.

Time to get out the old Fluke meter. On the meter, when the fans start-up the current surges to 33-35 amps then quickly drop to 17-18 amps. Tomorrow, I'll make a run to the parts store for some 35 and 40 amp fuses.

I tried it several times, and each time, on initial start-up the fans were drawing around 34 amps, but within a second or two the current went down to around 18amps.

There you go....FWIW.

John
 
Originally posted by OKTurbo
Thought I'd share some info....

I have the Ramcharger dual fan set-up on my 87 GN using the RC harness.

At the prompting of another tb.com member, I checked the harness wires while the fans were running. Just like the other member....the wires and harness on my fan were VERY hot.

So, I figured that I would rig up a separate relay to "hot wire" the dual fans. Hopefully this will save my original wiring from burning up.

What I have now is a 10ga wire straight from the back of the alternator through a 30A fuse (to the relay then) to the fans. The fan ground is 10ga from the fan connector to a bolt on the driver's inner fender (already two factory grounds there).

The factory wiring now triggers the relay. I was able to cut up the RC harness so I didn't have to butcher the factory harness....plus used the other connector for the fan.

Hooked it up....and flipped the manual fan switch....click...pop...blew the 30A fuse. Hmmmm....checked everything out. Nothing wrong. Replaced fuse and tried again....POP.

Time to get out the old Fluke meter. On the meter, when the fans start-up the current surges to 33-35 amps then quickly drop to 17-18 amps. Tomorrow, I'll make a run to the parts store for some 35 and 40 amp fuses.

I tried it several times, and each time, on initial start-up the fans were drawing around 34 amps, but within a second or two the current went down to around 18amps.

There you go....FWIW.

John
Click to expand...



I notice that on my spal fans also , I wonder how many amps the factory fusable link can handle?
 
When my stock fan was starting to drag, it would pull the voltage down enough to make the engine stumble at startupe and of course, all the lights would blink at night. I saw peaks over 50 A at startup and about 40 A while running. Never popped a fuse, though.

Since you bothered to add a ground wire, why not run it to the engine block? Otherwise the current has to go through that little (okay, what, 12 ga?) black wire from the passenger fender to the battery negative terminal (all the time) and then on through the big ground wire to the turbo bracket on the passenger head (if the engine is running).

Hmm, there's a reason to do your own relays: if you want the fans to run on high, turn one on immediately and wait 2-5 seconds to start the second one, to cut down the startup current surge.
 
Another way to do it, is to use a relay for each fan.
I couldn't find 50 amp relays so I decided to use a circuit for each fan. I have the Spal fans and yes they do draw so amps on start up.
That way "if" anything happens to one fan-heaven forbid- then you will still have one fan running. Plus you can use smaller gauge wire.
The 30 amp relays are only $3.99 at the part store.

Gary:)
 
I can put in a 40A fuse, but I'm wondering how long the 30A relay will last.

The dual relays may be the way to go. The biggest "automotive style" relays I found locally were the 30A, but you can get bigger ones.

www.waytekwire.com sells some 40 and 50amp Bosch relays.

I really didn't want to cut into the wires/connectors on the fans, but this may be the way to go.

Thanks,
John
 
revisiting..
Has *anyone* actually burned up a connector on a Ramchargers daul fan setup?? Is this something to worry about or not??
 
well i have the same setup as you guys, Rams Fans, 30 amp relay, 30 amp fuse and a manual fan switch. and that setup works like a charm. 1 10ga wire direct from the batt. w/ inline 30 amp fuse then goes to relay then i use the 3 plugs from the factory plug as a turn on wire for the relay then i have 2 10ga wires going from the relay to the 2 12ga wires on the fans.then i ground the fans and relay to a good ground and i'm done. this setup has been on my car for about 2 months and no problems at all. when i went to splice the factory high fan speed wire i could see that it got hot cause the wire was pink and the strands were melted together:eek: it's a good thing a accidently broke the adapter that they come with and then when i weht to hotwire it i found that the wires got hot and came to the conclusion to do it right.

Cody
 
i think you guys are overreacting, i got the dual RC fans with the GN adapter and my wires and adapter do not get hot , i also dont notice any stumble when the fans come on which is at 174 engine temp, tbey go out at 162 wiring has never been hot whatsover.
 
I've had the dual SPAL's for a while. I noticed they were getting flaky, and it was the ground wire that was burning hot. So I re-wired as follows, and all works well.
I have a twin post battery, so the fans and the stereo amplifier runs to the top positive terminal; the fan ground go directly to the negative top post.
I then used the stock fan wiring as the triggers for the 2 new 30A relays to drive the fans. On low, only the driver side fan is on. On high, both are on. {I didn't want the fan cooling off the turbo and hurting spoolup}. I included a 13V zener diode between the two positive relay triggers, so that when high kicks on (via hi fan switch) both fans are on. I chose 13V in hopes that if the car is off (with the fans running) and it's too much voltage drop, the one fan will shut off; I haven't seen this scenario yet.
 
Also have the RC fans and wired the RC fan to the stock fan conn and no problems yet.
 
Current amp draw (continuous) and airflow cfm are prettty much directly related in a modern fan design. Spal and Derale are the only two aftermarket manufacturers that rate airflow with true (not hype) cfm ratings. The rule of thumb is roughly 100 cfm per continous amp drawn. The Lincoln Mark VIII fan, which is one of the most powerful single fans available requires 100+ amps on startup, and almost 40 amps continuous. It blows about 4000 cfm (but it needs about 6.5" of depth to mount it).
 
if you will notice the RC adapter leaves out the middle pin in their connector. I just ran a piece of 14ga wire from the middle of the factory buick connector and then spliced it into the RC harness via the red wires, the reason for this is to be able to engage fans and still turn the car off. I also took a small piece of wire and placed it in between the hi and lo relay on the ground trigger side (green/yellow on 1st relay & green on the 2nd one) so when my fans turn on they are being fed by both the hi and lo relay. I also have a 10" fan on my tranny cooler all tied together. Since i "linked" both fan relays to act as 1 unit i am having no problems and absolutely no heat whatsoever in the RC harness. I figure that this causes the 2 relays to share the load. Hope this helps...
 
Well i would suggest 1 #10 awg relay and wire per fan each fused at 30 amps. However my derale fans draw 54 amps running and about 85 amps on startup so I went with #8 awg for each fan and relay!:eek: BTW i think i have a total of 6 fan relays to make this all work also. Fans run in series at 13 amps total , and in parallel with the a/c on or collant temps over 175 F
 
Originally posted by norbs
Well i would suggest 1 #10 awg relay and wire per fan each fused at 30 amps. However my derale fans draw 54 amps running and about 85 amps on startup so I went with #8 awg for each fan and relay!:eek: BTW i think i have a total of 6 fan relays to make this all work also. Fans run in series at 13 amps total , and in parallel with the a/c on or collant temps over 175 F
Click to expand...

A series parallel setup can not be run properly with the RC/Valeo fans because the two motors are not the same. One is slightly larger/more powerful than the other and draws more current.

I took two RC/Valeo fans and placed the two high power motors in one assembly. It was a bit of work as the brackets for the motors are not clocked the same. I had to router out one of the supporting legs to provide a nice path for the wires to exit from the motor. I rewired the fan timer relay so that it runs the low speed fan only. There is no sense in shutting down the motor and having the high speed fan draining your battery while the body of water in the rad is stone cold after a couple minutes. I use an adjustable thermostat in the upper rad hose to control the high-speed fan. High/low speed can easily be swaped for control via the FAST PCM.

For the heck of it I wired up a bunch of relays so that I could run the two speeds built into the Valeo motors. This in combination with the series/parallel wiring provides a total of 4 possible speeds. This was done for experimentation purposes and proved to have no practical purpose.

FYI Tyco (was P&B) make 70 amp automotive relays . I usually have a few in stock for special applications. You can get these through some automotive electrical supply houses. It is cheaper to use two Tyco 40A Weatherpack relays (as used by Racetronix) in parallel vs. a single 70 amp non-Weatherpack version.

BTW. The RC/Valeo fan setup is the ultimate deal for anyone considering a great fan setup!

Jack :cool:
Racetronix
 
hey Jack, please read your racetronics mailbox!! I'ver emailed a few times about your address.. :)

Thanks!
 
Originally posted by Black Car
Another way to do it, is to use a relay for each fan.
I couldn't find 50 amp relays so I decided to use a circuit for each fan. I have the Spal fans and yes they do draw so amps on start up.
That way "if" anything happens to one fan-heaven forbid- then you will still have one fan running. Plus you can use smaller gauge wire.
The 30 amp relays are only $3.99 at the part store.

Gary:)
Click to expand...

I agree.
I still have the stocker, but I plan to do this as well if I buy the dual fan setup. Is there a reason why guys don't wire them independently up to the existing relays?
Low speed relay to one fan.
High speed to the other.
And maybe add a smaller relay or something to jump from high to low to make sure low runs always when high fan is on.
 
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