Radio Wiring Problem
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Radio Wiring Problem
I have a 1990 F150 Lariat. I have two issues with wiring. Number one and most important to me is the radio. Somebody put an after market radio in it and it was a cobbled up mess. I picked up a factory radio for it, twisted and taped the wires back together as proper as I could. All the wire into and out from the radio are correct. The radio turns on and plays AM and wonders from station to station. Lights, seek button, tune button, FM, and preselects do NOT work. I thought this might be a radio problem so I exchange the radio for another. Same problem exists. I looks like there are two fuses associated with the radio and they are both good. Please help.
The other problem is: when I turn the truck off, the fuel pump continues to run. I can stop it by finding a middle spot on the F/R fuel tank rocker switch. I changed the switch and same thing. I have not explored any wiring to trace this problem yet, but if someone has run into these issues before, I could really use the help. Thanks
The other problem is: when I turn the truck off, the fuel pump continues to run. I can stop it by finding a middle spot on the F/R fuel tank rocker switch. I changed the switch and same thing. I have not explored any wiring to trace this problem yet, but if someone has run into these issues before, I could really use the help. Thanks
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
For the fuel pump problem,
You said you changed the switch, safe to assume tank selector switch being as that is what you where referencing at the time?
Did you check out the ignition switch? does it turn off all circuits in the "Off" position? key tumbler and ignition switch both work, the actuator between them, and adjusted properly? If you haven't I'd start there.
The radio,
When you say it wonders the stations does it find any, not real clear in your opening post.
If not never finds any continues to search up the scale then starting over again, did you plug in the antenna? Antenna also provides a ground path.
Red - ground
fuse #11 - yel-blk = power
fuse #8 - lt grn-yel = memory
main light sw - org-blk = LCD pwr
fuse #10 - lt blu-red = Illum lt
You said you changed the switch, safe to assume tank selector switch being as that is what you where referencing at the time?
Did you check out the ignition switch? does it turn off all circuits in the "Off" position? key tumbler and ignition switch both work, the actuator between them, and adjusted properly? If you haven't I'd start there.
The radio,
When you say it wonders the stations does it find any, not real clear in your opening post.
If not never finds any continues to search up the scale then starting over again, did you plug in the antenna? Antenna also provides a ground path.
Red - ground
fuse #11 - yel-blk = power
fuse #8 - lt grn-yel = memory
main light sw - org-blk = LCD pwr
fuse #10 - lt blu-red = Illum lt
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Yes, I meant the tank selector switch. There doesn't seem to be problem with the ignition switch as everything turns off and I have no battery drain. As I said, I haven't really checked into the fuel pump problem yet.
I thought the radio could be a ground problem, but the aftermarket radio that was in it worked ok. There are no lights, LED or function in any of the buttons. The AM signal does just keep wonder through the band and never stops. What's weird is, the first radio I tried did the same thing, so I can assume there's a wiring issue. From the harness, all the wires are placed correctly.
I thought the radio could be a ground problem, but the aftermarket radio that was in it worked ok. There are no lights, LED or function in any of the buttons. The AM signal does just keep wonder through the band and never stops. What's weird is, the first radio I tried did the same thing, so I can assume there's a wiring issue. From the harness, all the wires are placed correctly.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
The fuel pump takes couple things to run, first key on power to it via relay system then the computer to provide the ground path timed / response to PIP signal.
PO might have jumpered couple circuits to make it run manually couldn't or wouldn't fix it right, is there a switch on the dash that's not factory you haven't figured out what it was for?
No history to go on have no idea if for example, this is a new problem one it didn't have yesterday? or truck is new to you condition it was in just bought it couple days ago?
Truck as shipped from factory key in "off" position fuel pump doesn't get power or ground to it either one.
PO might have jumpered couple circuits to make it run manually couldn't or wouldn't fix it right, is there a switch on the dash that's not factory you haven't figured out what it was for?
No history to go on have no idea if for example, this is a new problem one it didn't have yesterday? or truck is new to you condition it was in just bought it couple days ago?
Truck as shipped from factory key in "off" position fuel pump doesn't get power or ground to it either one.
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There are no 'non-factory ***** or switches, Mickey Mouse mods. The fuel pump problem has been there since I got it a month or two ago. The radio, as I said was an after market that kept popping fuse #10. The wiring job was a mess and I had to replace the plug in's for the radio. I did this just by twisting and taping the wires back to the harness as per color.
You said in your first reply, the antenna provides grounding, so I went out and checked my ground (red wire) at my twisted connection. I brokle that connection and the radio continued to work as it was. It did make noise and change a bit when I reconnected the red wire, but still not luck in lights and function. I'm wondering about the ground withing the harness (the factory ground point) Would you know where that's at physically?
You said in your first reply, the antenna provides grounding, so I went out and checked my ground (red wire) at my twisted connection. I brokle that connection and the radio continued to work as it was. It did make noise and change a bit when I reconnected the red wire, but still not luck in lights and function. I'm wondering about the ground withing the harness (the factory ground point) Would you know where that's at physically?
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
There are no 'non-factory ***** or switches, Mickey Mouse mods. The fuel pump problem has been there since I got it a month or two ago. The radio, as I said was an after market that kept popping fuse #10. The wiring job was a mess and I had to replace the plug in's for the radio. I did this just by twisting and taping the wires back to the harness as per color.
You said in your first reply, the antenna provides grounding, so I went out and checked my ground (red wire) at my twisted connection. I brokle that connection and the radio continued to work as it was. It did make noise and change a bit when I reconnected the red wire, but still not luck in lights and function. I'm wondering about the ground withing the harness (the factory ground point) Would you know where that's at physically?
You said in your first reply, the antenna provides grounding, so I went out and checked my ground (red wire) at my twisted connection. I brokle that connection and the radio continued to work as it was. It did make noise and change a bit when I reconnected the red wire, but still not luck in lights and function. I'm wondering about the ground withing the harness (the factory ground point) Would you know where that's at physically?
Can get diagrams for stereos after market suppliers but it be in wire color/function only, wouldn't include location of grounding points for example. Just what color the wire should be.
With a meter you could test it easy enough, end of suspected ground wire/s for continuity to any good ground point in the cab, such as the column support brace or throttle/gas pedals bracket.
When in doubt when I install stereo question speaker leads for example I'd pull speaker look at the source. While speaker will work if both wires are connected if polarity is wrong no stereo separation.
Key "on" power and memory power wires again use meter to verify each one, colors/diagram might be wrong. Test them make sure they do what the diagram says they do.
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Cargo Master
Joined: Nov 2013
Posts: 2,168
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From: South Central,MO
I had a problem with the pump on my 90 running all the time also. In the original factory plug there was a piece of it missing between two of the terminals. As it aged and the wires sagged and moved these two terminals touched turning on the relay. It took me 4 years to find it and then it was a freak accident. I was doing something under the hood and bumped the relay and heard the pump cycle. Bumped it again and the pump cycled again. Pulled out the relay and noticed the missing piece. Went to the junkyard and got one that was whole, replaced mine and no more problems. Might not be your problem but a good place to start.
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The problem with the radio turned out to be the 12v constant wire (green/yellow). I did not try to find out why there was no power coming out of the harness (in-line fuse perhaps?) I just ran a fused wire from the cigarette lighter and it works. Thanks you guys for the help. I'll get out there next and chase down the fuel pump problem and post any resolutions.
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