I talked with Kyle the other day, told him my problem, he said he would email me a schematic. of my electrical system. My interior lights blew and when I install another fuse, it blows on contact. I have a 1987 Volvo 740. I have a constant 12VDC at the fuse, even with the ignition off.
put a fuse of a higher rating in it it will have 12 VDC if your doors are open post if that doesn't work
oh lord, never put a higher amperage fuse in if the factory spec fuse blows, it's that rating for a reason. THERE IS A SHORT A higher amp may not blow and cause an electrical fire. Everything will be 12 volts, that is the system voltage on the car. Amperage is how much current will pass, all at 12V
http://www.autoelectric.ru/auto/volvo/740/1989/740-89.htm ..has full schematics for 1987 Volvo 740
The schematic for the 1987Volvo was helpful, but I need to ID the different relays on the relay panel. Kyle was very helpful when he told me that !@VDC is always present, but the ground is what is switched off/on. This tells me a relay may be stuck. Which relay is the radio/interior lights/trunk relay?
I don't think it has a relay for radio, the current is not enough to require one, it just passes through fuse to radio. But here are a couple place to look, Hope you have better luck. I will put each in a different box to make it easy to hyperlink.
I went to rockAuto.com and and Auto-Zone O'Reillys and about 3 others...and none list a relay for a radio or interior lights for '87-740. Yes, there will always be 12v at the fuse, that's what powers that and everything else. Different things consume varying amounts of power, or amperage. But all at 12V
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