Ok I no I have ask once before about this but I have no headlight or dash lights or taillights or brake lights but I do have turn signal and a new switch headlights are new and work I have tested them ... Agin any help would be great thanks
Since the headlights and tail lights both take power from the 50A fuse in the fuse box under the hood, it can't be the problem. Once the power gets to the fuse box, they are supplied by separate power sources. The headlights, taillights, marker lights and dash lights all take power from fuse #8 in the inside fuse box mounted to the firewall above the break pedal. I would check that first! They all have separate grounds, so it's just unlikely that all of the grounds went bad.
When you stick the key in the ignition do you hear the buzzer that tells you the key is in? The reason I ask is that it is also powered by the same fuse.
From the bottom left corner of the fuse box, it is the 20A two fuses to the right and one up (right above the aluminum clad fuse).
The next suspect would probably be the switch itself, if the fuse is good.
The only difference seems to be that you'd have a fusible link rather than an under hood fuse box, but I don't suspect that anyhow. Looks like on the 1989, fuse #8 underdash (labeled PARK/TAIL) is likely the cause. 20A fuse in the center of the box above the aluminum clad fuse in the bottom row.
O.K. next would be to see if the plug at the switch (going in and going out). On the plug for the switch there should be four wires if you put a jumper from the red/black to the blue wire do the interior and running lights come on? The only ones that won't come on should be the headlights (different wire).
Well small update I bought a new relay and it did not help ... I traced the wires back and the were good and good connection so I'm at a loss but maybe a new after market switch would do it at this point ......
Could run a hot from the battery to where the red/black wire is on the switch with an inline 20A fuse. The you get the power back and still have good wiring the whole way.
All of the wiring after the switch is working, so it can't be relay. When we jumped from the battery to where the red/black connected, all we essentially did was bypass the fuse, so it should work. There could be corrosion between the two inside/outside halves of the fuse block. The weak connection would explain why the power disappears when it comes on.
I think your switch is fine, especially since none of the three worked. The switch worked great once it had strong power going to it. I'm 99.9% positive that if you just replace the red/black by going straight to the battery, with an in-line 20A, you'll be all set. If you go with aftermarket switches, you still have to run another power wire anyhow. Plus if you go with aftermarket, you'll have to run two separate switches (one for running lights/dash and another for headlights). Plus you'll need to wire in two relays to control them also. I'm I could make up a diagram for you, but I'm thinking it's WAY more costly, not to mention complicated and not really necessary.