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[KC6RWI]

I know there are alot of techs on this forum, that is why I dare to post this slightly off topic subject. I have fuse problem on my blinker and 4 way lights. I know how to look for problems, isolate, remove bulbs, check resistance on the load side of the blinker relay. My blinkers will work at a normal flash rate and blow a fuse, how that be? I was thinking it was a ground problem, but then  every bulb is isolated and has a ground wire.
I am about to take to an electrical repair shop, but I wonder how they do it,what tools they use, every car is different and there are a myriad of possibilities.
the car is a 95 chevy.

[W9WQA]

a ground problem would typically mean a poor ground or none.
reduced current or none. opposite of your problem.
you might look at current with a meter...

[KC6RWI]

Yes, I agree that makes sense, poor ground makes a incomplete circuit.
I read somewhere, probably here, that a installed radio should be fused on both positive and negative, the reason is that a bad ground could cause current to flow thru the radio due to some other fault in the car. I may not have that exactly right, but that would could have been my question.
Just to clarify that a bit because it sounds wrong, I think its dealing with parts of a car that may not be at equal negative potential due to panels rusting or separating.

[K0UA]

I would start by replacing all of the bulbs. It is possible (but rare) to have a defective bulb that has a filament problem that draws more current than it should. Also check each socket very carefully for water ingress and possible corrosion to ground drawing some extra current. Start there. Then look for a possible pinch in the wiring harness. A chafe where the wire intermittently touches ground and blows a fuse but works normally "most" of the time.  Start with the bulbs and socket inspection, and pray it is not the wiring harness, because that can be a real bear to find. Good luck.  73  James K0UA

[KC6RWI]

Yes, a bad bulb, though rare may have a problem, they are 2 filament and alot of heat. It just seems to me that usually a short is going to be a physical movement of wires, something that is touched or moved. I am on the hunt for now.

[K5LXP]

Divide and conquer - does the fuse blow when just the right or left blinkers are activated?  Or just the 4-way flashers?  Does it blow when all the bulbs are removed?

One of the tools used is a ballast - a resistor or current limiting device put in place of the fuse that doesn't blow, and reduces current to a safe level (a series lamp works well for this).  From there you can measure voltage at various points of the circuit, and the point where voltage is lowest is where you'll find the fault.

Mark K5LXP
Albuquerque, NM

[W1RKW]

is the fuse the correct size?

[KC6RWI]

All good suggestions, yes, correct value on fuses, fuse blows in normal flash rate. Divide and conquer, I have put an ohm meter in place of the fuse, and checked also on the other side of the flasher unit that see's the load on the flasher.
On the divide and conquer, I use the word isolate, I could remove every bulb thats involved and possibly find the branch that is grounded.

Could be a brake light switch or ignition switch, but somehow I doubt that. thanks again

[AC2EU]

Damaged or water-logged bulb socket somewhere? Mouse chewed a wire?
I like the try left side , then right side idea to see if everything is working in order to narrow it down a bit.

Not a bad ground but excessive current issue as preciously mentioned.

[KM3F]

Don't forget.
If you measure the resistance R, I= E/R.
Is the I result close or greater than the fuse value?
If yes, expect the fuse to blow.
All it takes is a bulb filament broken and grounded on the hot side of the circuit inside the bulb.
Note; the system voltage will be greater with the motor running than with it off.