Cig Lighter fuses keep blowing

[Jordan]

1991 GMC Sonoma compact pickup

So i am guessing the previous owner installed an after market lighter socket as it has an inline fuse behind it. The lighter is also connected to a blade fuse in the fuse box. I checked continuity on the lighter and I have a closed circuit. When I got it the online fuse was five amps. I tried a few AGC fuses until they stopped blowing. The blade fuse is supposed to be 20A so I settled with a 20A AGC behind the lighter. But now when I install the glass fuse, the blade fuse in the fuse box blows! What is happening here? I thought this would be simple....

 

[mickfred]

Check there is not a screen or paperclip fell down it

 

[telectrix]

what rating is the blade fuse ? 10A is normal for a cig. lighter . also, see if it blows with the lighter part out of socket.

 

[Jordan]

The blade fuse is 20 and that’s also what the manual says to use. The socket is clear of debris and has no lighter to put in it. (I just want to use it to power devices)

 

[Deleted member 26818]

If you have a closed circuit on the lighter, then you have a short circuit.
Should be open circuit.

 

[Jordan]

Well I mean to say the positive and negative are hooked up nice and clean

 

[Deleted member 26818]

Taking your multimeter, remove the in line fuse and insert one of the probes. Place the other probe in contact with a known ground/earth and check for continuity.
If there is continuity, there is a short circuit.
No continuity, there should be no problem.

I take it that the 20A blade fuse does not blow until the in line glass fuse is inserted?

 

[Jordan]

Great thanks I will try that tonight. And yes, blade fuse blows only when tube fuse is inserted.

 

[Deleted member 26818]

Great thanks I will try that tonight. And yes, blade fuse blows only when tube fuse is inserted.

That suggests, the wiring up to the fuse holder is ok.

 

[Jordan]

So would that mean it’s just the socket doing this for some reason? It’s definitely clear of debris

 

[telectrix]

if you check for continuity from the lighter side of the in line fuse holder and the body of the lighter you should get open circuit.if it's a low ohms reading, then the lighter socket is buggered.