Rear lights fuse keeps blowing

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Just got a 1996 sportrack spent the weekend putting a new stereo in it and cleaning it but now when i turn on the lights the rear lights fuse blows and the dash lights and the side lights dont work checked my radio connections and all the obvious stuff but cant trace the fault any ideas?
ps.
the stereo still works!

Fused

Check the obvious, have you trapped a wire, or caught it with a screw and shorted it out, or is there a fault elsewhere on the wiring loom, begin by testing to earth with a multimeter, if it shows a short it is prudent to begin behind the dash as this is where you have disturbed wires.

Check the loom for chafing, or where wiring passes through a metal panel, grommetts deteriorate with age, and chafing can cause wiring to short.

If not it is a matter of working from one end of the loom, disconnecting sections until you find the problematic section and isolating the problem.

FUSE BLOWN

Firstly recheck the wiring to the radio for shorting as mentioned. If as you sa all is well disconnet the radio live supplies and see if that improves the situation. I suspect it won't.

You say you cleaned the car, did you use a power hose and has water got into the rear lights. I would expect that your sporty has those set in the rear bumpers. They can be swines to get out in tact as the screws corode. If and when you get yhem out check for blackening of the bulbs and also check the wiring to the lights for chaffing. If all is well then grease the screws well and put that lot back and return to the dash. Check all the wires you have connected to ensuring that bo connector is showing bare metal that is shorting on the body work. A good number of radios require a lihting live so that at night with the lights on the facia dims. What connectors did you use, the crimps and those scotch connectors are renowned for failing and shorting. Use Japanesse fully sheathed connectors and spades with covers on both Live and Earth(neg) connections. It is possible that as you push the radio back into it's housing a bare live is fouling on the bodywork and I suspect it would be the one from the lighting circuit.

It is I'm afraid a case of checking and illimination but usually something small that has been over looked or not using insulation sheaths on all connections.

Good Luck

OLDMINIMAN

Wires correct?

Any chance you have reversed the radio connections with earth/positive wrong way around? Lights could be branched from the same circuit as the radio and now fusing the light circuit due to direct connection of positive to earth. Chasis of radio could now be + and connected to negative of lighting circuit.

Problem solved!

After a bit more investigation and everybody's suggestion checked the earth to the loom and it seemed to become live with lights on so Ive took it out and connected the earth straight to the chassis- problem solved now i can drive with the lights and the radio on!!!
Thanks for the help dave i...

IMHO it was the radio circuit of new radio.

Dave.
Pleased to read it is solved. Sounds very much as if the new radio has reversed polarity so the earth wire would indeed become positive, hence continual blown fuse etc. Wink