[Fists] A fuse problem

[Stan Reas]

Hi Folks:

I have run into an interesting and baffling problem in my mobile installation.

I have a Ten-Tec Scout.  I supply power from the "Power Outlet" located on 
the front dash of my 1999 Dodge Grand Caravan.  These outlets were 
previously called "cigarette lighters".  The  outlet is rated 12V - 20A as 
printed on the rubber "stopper" which can be installed when the outlet is 
not in use.

Until recently I have had no problem with this installation.  But recently 
I have had a rash of blowing the 20 Amp fuse supplying this circuit.  The 
baffling part is that there is a 12 Amp in-line fuse in the wiring from the 
outlet to the Scout.  And, this fuse does NOT blow.

The first time the 20 Amp fuse blew, I was in contact with Howie, WA4KER 
while on my way home from the golf course.  Rather than stop to determine 
the cause, I proceeded home and checked the 12 Amp in-line fuse.  It was 
OK.  Then I found the 20 Amp fuse located in the fuse compartment under the 
hood was blown.

I replaced that fuse and thought the one that blew may have just been a 
"weak" one.  However, about a week later, this new 20 Amp fuse blew as I 
was completeing a QSO in my driveway.  Again I replaced the fuse and 
everything was fine for quite about a week.

I operated mobile in the Ohio QSO Party.  While parked in Ashtabula County 
with the motor running this new 20 Amp fuse blew.  When I lifted the hood I 
noticed it was quite hot in the engine compartment and I surmised that the 
ambient temperature in the fuse compartment had contributed to the blowing 
of this fuse.

We made a trip to Atlanta this past weekend to attend a wedding.  I 
encountered no problems during this trip.  Of course we were running at the 
70 MPH speed limit of the interstate.  I had some QSO's during the 
trip.  The most interesting ones were helping Norm, WB4YBY get hooked up 
with Bernie, N7YY so Norm could get that elusive Montana contact he needed 
for his WAS - CW.

Then today as I was driving into Rocky Mount, VA in QSO with Jose, KA5ZBP 
in Irving, TX darned if the 20 Amp fuse blew just as I was signing off with 
Jose sending "73".

Now ALL these times the 12 Amp fuse in the wiring from the Power Outlet to 
the Scout did NOT blow.  When I questioned the people in the Service 
Department at the Dodge dealership where I bought the car I was told that 
the "spikes" occurring when cell phones are turned on can blow this fuse.

I explained that I did not have a cell phone and that I had had this setup 
for over three years with no previous problem with this fuse blowing.  Why 
should it suddenly begin now, and why doesn't the lower amperage 12 Amp 
fuse either blow first.  They just shrugged their shoulders.

Now I know most mobile operators will say: "Run a separate circuit directly 
from the battery for your radio - fused in both the positive and negative 
leads."

But it sure is convient to use this Power Outlet, especially when moving 
the rig from my car to my wife's Plymounth Grand Voyager - WHEN SHE LETS ME 
USE HER CAR, that is - Hi! .

And, I'd sure like to know why that 20 Amp fuse blows.

The Scout runs about 40 Watts output into a Hustler Antenna mounted on the 
left rear of the van.

One chap suggested that I might try shooting some "Contact Cleaner" into 
the terminals of the fuse block for this circuit.  He thought there might 
be a high resistance at the terminals of the fuse which increased the 
heating of the fuse.

Have any other of you folks had a similar problem using this "Power Outlet" 
to supply their rigs ?

I'm baffled !  Any ideas out there ?

73, Stan - K4UK