Run Cooling Fans Flat Out ? / Bob Zilla

[ZillaDelorean@xxxx]

Every summer, like clockwork, someone will suggest running the Cooling fans 
constantly. 
Hey, it's an appealing idea. 
The car needs to be cooled so why not just run the fans flat out ? 
What harm could it do ?

Here's the rub:
If you choose to pass the current needed (20 Amps minimum ) through both the 
stock relay sockets ( blue fan fail socket & fan relay socket ), you will be 
running some of those terminals at their design current limits. That's 
assuming the car was brand new, the terminals are very tight and completely 
without oxidation ( tarnish ).

Well, the car is 20 years old. It is likely that connectors have been 
jockeyed in and out of these sockets for many years. The more expanded and 
tarnished they become the less current they can pass efficiently. As a 
result, they are likely to overheat and melt down a relay socket.

To test for loose connectors see:
http://www.deloreanparts.com/zilla_014.htm

To restore correct terminal tightness see:
http://www.deloreanparts.com/zilla_013.htm

If you choose to run your fans continuously in this fashion you will run a 
relay socket melt down risk. What's worse, is that you stand to damage the 
insulation on the stock DeLorean harness wiring just outside the relay socket 
leading to the terminals. These wires begin to overheat and damage the wire's 
insulation. While you might figure that a quick trip to the local autoparts 
store will provide you with the proper wire to repair the damage, it is VERY 
unlikely that they will have the high temperature wire needed to do it 
correctly. 
FYI: Soldering these wires and black electrical tape have no place here as 
well. This is a wire crimp zone only.

As if things aren't bad enough, running the fans continuously overtax the 
Alternator. With the fans running, the Alternator is required to supply 20 
Amps Min at all times. That's assuming nothing else in the car is running. 
Very unlikely ! At night when cooling is needed the least, you are also 
running the head lights ( another huge draw ). 
What, you haven't had enough alternator problems already, you want to tax 
it more ?

The temptation to modify the stock relay wiring configuration is often 
appealing in the short term. In the long view it's not the way to go. Should 
you EVER decide to sell your car, the next owner will have no idea what 
you've done. Many new owners can attest to this. 
Decoding the "new" wiring mystery is not fun. 
You didn't improve the car, you obscured an underlying problem.

The Beauty and Magic of the "Duty Cycle".
Every Engineer is familiar with this concept. It allows a device to work way 
past it's design limits. This holds true for the DeLorean. By allowing the 
cooling system to Cycle, it runs at nearly a 50% duty cycle. This means in a 
typical AC cycle configuration, it passes current for only half the time, 
allowing the entire electrical system to cool down. This is how the terminals 
in the relay sockets can work past their design limit. The Lotus Engineers 
knew EXACTLY what they were doing. If your cooling system is up to snuff it 
will work just fine. 

When you decide to run the fans continuously to remedy a poorly functioning 
cooling system you are treating the symptom and not the cause of the problem. 
Do yourself a favor: 
FIND THE REAL PROBLEM AND REPAIR IT PROPERLY.

Bob Zilla


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