Alright, we had a pretty good debate in another thread regarding guys that are burning up relays with there e-fan swap harnesses. Since I have been rewiring my truck, I got in on the discussion and built a harness using metripack 280 terminals for the relay and mini fuse (they package nicely). The first harness had 35 amp relays and 30 amp mini-fuses. Testing was done using factory fans from my 06 silverado. When I clicked on the fans using the first harness I built, it popped the 30 amp fuses immediately. It was discussed that the harness was wired incorrectly, I checked and it was not.

The second harness I built used std. 1/4" terminal relays and fuses. The relays are rated at 45 amps and the fuses are 30 amp. Clicked the fans on and they worked perfect. Scratching my head wondering why the first harness I built with 30 amp mini fuses wouldn't work. I mean a 30 amp fuse is a 30 amp fuse right??? except for the fact that one is a 2.8mm terminal and the other is a 1/4" terminal.

So I went and bought a circuit tester that will read upto 400 amps DC. Brought it home, hooked up the fans to do some current testing. The results were interesting to me especially comparing to some stuff I've read in other threads/forums.

Fan 1 running full speed (12v) was drawing anywhere between 23.5 and 25.5 amps depending on the location I tested in the harness.

Fan 2 running full speed was drawing anywhere between 25.5 and 27.5 amps depending.

I did some testing on amp draw at fan start up (12v) and saw a peak of 39 amps. Amp draw at start up is just a spike for a split second, and quickly falls back to its normal operating range.

I'm no electrical engineer, but it seems to me that the significantly smaller terminals create enough resistance to not be able to handle current spikes (fan startup) as well as the 1/4" stuff.

Take from this what you will. Just thought I would pass on some real world technical data.

 

I believe there are fast blow and slow blow fuses. Both rated the same, but one will allow a little more for startup current draw.

 

Can't tell you anything about your testing, but I can tell you what I know based on observation.

When I built my harness, I used ATO fuses and never had a problem (never used the minis).

The '05+ factory harness uses the Jcase style fuse.

 

Good information to know.

 

Sounds like you proved some theory with the different size terminals for sure, good findings

So what size (amp) fuses did you end up using? With 39 amp max at start up, I'd have to assume that a 30 amp fuse wouldn't be up to the task??...

BTW, did you use an inductive ammeter or one hooked up in series?

 

He probably bought the inductive clamp style.

Can you imagine the kind of tester to handle in series 400 amp current draw?
The cables or input on that thing would have to be massive.

 

Screw fuses, I have a 40amp auto reset circuit breaker on my perma cool fans

 

 

Well, I'm gonna use 30 amp fuses as they seem to work well and will blow before the thing burns down if there is ever a problem. I put these fans through a pretty ridiculous torture test with the 30's and they held up. Switching the fans on/off repeatedly and also ran the thing for 10 minutes straight and then jerked the switch off some more.

It's an inductive tester.

 

Where'd you get this from?