Re: Fuses

["John Hervey" <dherv10@xxxx>]

David & Group, 
I agree with you in most case of fuses, But remember. The fuse is 
supposed to be the weakest link in the system to stop futher damage 
to circuts, burning up wires or protecting sensitive items. There is 
a reason the fuse may heat up and melt and not blow, but putting in a 
larger fuse, well you might as well just hard wire it and forget the 
fuse. I case of the cooling fans in the De Lorean, I see 20amp fuses 
all the time and thats to much. If the motors are in good running 
order then a 15Amp fuse will work just fine. It will handle the 
inrush current and run normally at room or car temp. If 20 amp fuses 
are used, then you stand a chance of burning up wires in the motor 
and creating more damage due to the overheating wires and melting 
wires in the motor circut. The larger fuse acts as a heat sink and 
absorbs the heat of the overload instead of reaching the blowing 
state. The damage will also extend to the wires it's laying next to 
if the plastic melts. I have put current meters in each circut and on 
my car at 45,000 miles the fans pull about 14 amps ea. So I fuse with 
15 amp fuses. ATO & ATC fuses the De Lorean car was designed for by 
the current chart at 15 amps will handle 20 amps for 1 sec under 
normal conditions. As temperature in the compartment goes up then 
current goes down. 
Last but not least, I have been asked several times how to judge the 
current size. With out the current meters. Then put in a low current 
and go up till it stops to blow. Then stop there. If ( Big IF ) the 
ambient temperature go up then current goes down, it may need to be 
adjusted in heat. I also leave the cover off the fuses in the De 
Lorean to help get rid of heat. 
John Hervey 





> Having just done some electrical work on several "old" cars I have 
> noticed something worth mentioning. I found that many of the fuses 
> were not in the correct places or were just the wrong size. 
Sometimes 
> all that is required is to just move them into the correct 
positions 
> but I have also seen all replaced without regard to the correct 
> values. In some cases the fuses are too small but in most they were 
> too big. DMC Joe has a fuse layout or you can look in the owner's 
> manual or workshop manual. I think it would be a very cheap form of 
> insurance to make sure that the proper size fuse is in the proper 
> position. It would also be a good idea to keep an assortment so you 
> can always replace a blown fuse with one that is correct. While you 
> are in the fuse area behind the passanger seat make sure that the 
> blower fan and cooling fan circuit breakers have been replaced with 
> the correct bigger ones and that all of the wires do not look 
> overheated. If you still have the jumper wire for the cooling fan 
> relay carefully examine it for signs of overheating. There have 
been 
> cases of electrical fires so it is an area of concern.Many people
> have 
> had their hands in the cars over the years and sometimes they 
didn't 
> always know what they were doing. If you aren't an origional owner 
> (not many of us are) then you don't know who did what.This is an 
> excellent winter project and you don't have to be a mechanic to 
check 
> this area.
> David Teitelbaum
> vin 10757