radio wont turn on while lights are on?

91, b2600, stock lighting

ive got this odd issue, when i turn my headlights on the radio will not turn on...also when i crank it up it will turn off like it dosent have enough power...its a cheap 99 dollar dual deck from walmart...using the stock wiring...and all soldered together....checked all the grounds etc..everythinbg is good (now) but the problem remains...any ideas guys?...im trying to avoid direct wiring the radio to the battery

oh yeah...new battery...terminals are ok...wires are not all corroded from the battery

Start the engine. Turn on the headlights. Now check for positive voltage with DC voltmeter/multimeter at the red lead and at the yellow lead for the stereo. Question 3: did you run a new ground wire for the stereo?

Question 1: does the stereo work when ONLY the parking/running lights are turned on?

Question 2: When you turn on the head lights, do the running lights, taillights, and instrument cluster lights stay on?

Where EXACTLY is the radio grounded?

It sounds like maybe you've got the ground wire hooked to the red/black dimmer wire.

The red/black wire will show a ground using a volt meter with the lights off. When you turn the lights on, that wire goes to a varied positive voltage.

Make sure your radio ground is a solid connection to the body of the trick, with any paint scraped away. Usually on these trucks, one of the 4 screws that hold the metal radio console bracket to the tranny hump works good.

Make sure you have the constant 12 volt wire hooked to your radio yellow wire.

Make sure you have the switched 12 volt wire hooked to your radio red wire.

Let us know what you find.

i couldnt find a wire diagram...so i used my meter to find a ground...and probably did hook to the dimmer wire as a ground ....thats probably my issue...i will run a stand alone ground to the body and see whats up thank you for the heads up

correction, my haynes manual does not have a wiring diagram that includes the radio circuit....or i just didnt see it...

Exactly.

I know on my 2200 the fuse for the radio is marked door? or maybe i'm reading the wrong side label but i don't think that is the case. I will check in a bit to let you know. and grounding it to that metal bracket is perfect, I'm not wired into my ignition switch I have to cut my radio on/off manually when start and stop. But i don't have any power drainage issues at all, and connected my ( yellow ) memory wire in with my power wire from the radio both to the line from the battery. I have no issues keeping pre-sets or anything.

Yeah, that works...but it will only take once leaving your radio on overnight (or maybe longer) for your battery to be dead in the morning. Getting the constant straight from the battery is fine, in fact, back in the day, most alpine decks recomended the constant going straight to the battery since the internal amps had "so much power".

I'd still run the red wire to a switched source just so that the radio is off when the truck is off.

My 1970 VW had the dealer-added AM radio, and that was wired as constant on.

My 1971 VW had the dealer-added AM-FM (mono) radio, and that was wired as switched-on.

My guess is for the VWs, it depended on the guy actually wiring it up. So when I went cassette on both (Duh !!!!), I just kept the same power source; that was before the cassette stereos had clocks and presets,

nailed it! thanx a ton .....i ran a new ground taped off the dimmer wire and poof..... no more amp shortage!