I got my fan off of a 97 Lincoln Mark 8 and I picked up a Painless electric fan wiring kit, my question is how many amps does this fan draw? It looks alot more than the 30 that the wiring from Painless supplied can handle.
Thanks,
Mike

Great question!! I had this very same question when I installed mine. After reading all of the websites stating MONSTER amp draws I was a little concerned about getting my charging system sized correctly. Well to dispell all myths I went down to my friends shop and hooked it up to their machine.


At startup 30 amps.

At 12 Volts(alternator not charging) 18 amp continuous draw.

At 14 Volts(alternator charging) 22 amp continuous draw.

It pulls a lot of amps, but it's nothing like the 40-75 amps that some sites claim!

The Mark VIII is a two speed fan isn't it? Is that the low speed draw, or high speed?

That's on high....You have to wire it differently to get low, which I didn't.

Hmmm :confused: Something is amiss here? I have tested several of these fans over 30+amps continuous on the car. Most are about 36 amps@13.5volts. And, about 100 amps peak inrush/startup at about 20msec duration. In the post above...if you are measuring the "startup" current with a good digital or analog meter as opposed to a scope...you will not see the correct inrush or startup current figure. Both animals are too slow to pick it up and do not sample fast enough.

And to further corroborate my findings I offer this experienced site which is a boon of information on this very subject at http://www.geocities.com/smithmonte/Auto/MarkVIII_Fan.htm which they warn... [b]"Note: The Lincoln Mark VIII fan will draw continuous currents of 33A@12.0V & 42A@14.4V, and has a starting current in excess of 100A! You will definitely need to upgrade your alternator to a 3G-130A (or at least a 100 amp anywho in my opinion...a 140 is better)!

Perhaps the above poster had voltage drops in the wires/connections that posed an impedance to the circuit. To flow 35 amps takes correctly prepared leads and connections to NOT inhibit current. I am betting that is the problem here with the low readings.

The point is really moot anyway, but a very good question regardless. The real answer your question directly is...the 30 amp relay supplied will bite the dust quickly. Run a V7 Tyco series automotive relay (70 amp) for this application. You can find the general data sheet at http://www.newark.com/product-details/text/CD121/60873.html and a whopper sheet at http://relays.tycoelectronics.com/datasheets/Automotive_Relays/VF7_DS.pdf :D

They can be had at www.newark.com (http://www.newark.com) but have to be phone ordered. ;)

Also note the "freewheeling diode" discusion. This is a very good feature to build in to any large fan circuit. It will diminish battery bus line spikes and save relay contacts. The Tyco above is good for a couple hundred thosand operations by the way at the rated fan current!! :cool:

Hope this does it!

I can't answer your technical questions exactly. All I know is they used their SUN electrical machine thingy mabob that they use to test out auto electrical systems. They were able to monitor the alternator output, voltage drop, etc. They had some kind of inductive thing that they put over the power wire to the fan to read the amps.

My charging/power wiring has been upgraded to the "madelectrical.com New System" so I don't think that there is any voltage drop.

All I know is they said 18-22. They could be wrong, but that amperage draw corresponds with the performance of my 94 amp alternator with everything on.

paulm, the machine used by your shop, depending on age, is either a VAT-28, or VAT-40.

Yes, an O'scope is needed to measure the current rush of startup.

As an elec motor gets hotter in temp, the more current it draws.

One could rig up an SCR circuit to control the fan, SCR = Silicon Controlled Rectifier, meaning a diode in the buss line wired directly in line of BAT voltage. To allow current to pass, turn "ON" the SCR to allow it to conduct. Thereby, suppliying voltage to the fan motor. Thus eliminating high-current relay contacts. How come OEM's haven't thought of this idea?

Everette......SCRs are not very well suited for solid state relays for this application. The reason is that an SCR needs to break the voltage (remove the current flow completely)in some matter to reset. Therefore once you turn in on the only way you could reset it would be with another relay or transistor to break the circuit. I guess you could put the mechanical thermal sensor that is nothing but a relay, but would have to take the brunt of the TOTAL current.

FWIW, solid state relays use power transistors to accomplish this moreover. They are out there but actually a good automotive relay is as good as it gets. New cars still come with relays because of their inherent reliability and costs. The relay mentioned above will operate easily within the engine environment at full load for hundreds-of-thousands of operations. For $6 that's pretty good and one of the most reliable components on your car. If you put a "freewheeling" diode in the circuit, contact life is not an issue. The relay will quit due to constant temperature cycling if under the hood first.

Okay. I didn't think about turning it off.

You guys got way too technical on me! I think that I'll wire up the free wheeling diode to go easy on the bosch 75 amp relay though.

I'll take it to another shop and have it tested again....Just to make sure since you have tested several and get 36 amps and they said they only saw about 20 amps.....just to make sure, I don't want to be misinforming anyone!