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Eric, Automotive Repair Shop Manager
Category: Buick
Satisfied Customers: 29733
Experience:  20+ yrs. experience as repair shop manager and technician.
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Factory radio converts dim signal (voltage) to PWM signal

Customer Question

Factory radio converts dim signal (voltage) to PWM signal output to A/C display. I have aftermarket radio, lost dim capabilities in A/C unit. Need to convert voltage to PWM. Most people gut factory radio, but I had no luck with this. I ordered chip from China, waiting for it but have to choose 1kHz output or 8kHz. 1995 Buick Roadmaster have you heard of this issue?
Submitted: 7 months ago.
Category: Buick
Expert:  Eric replied 7 months ago.


I am sorry that you have not been helped yet. I just came online and saw your question

Ok, I need to know if you hardwired the aftermarket stereo or used appropriate wiring harness adapters, as well as brand and model of the new stereo and the last 8 of the vin number of your Roadmaster so that I can pull the schematics to it

Customer: replied 7 months ago.
VIN: 1G4BT52P3SR420496
The prior owner cut the wiring harness, and just twisted the wires together. I went ahead and connected all the wires with butt connectors. I did order a new harness, but I do not see a need to use it now. The radio is Dual XD250, and I also have a Galls ST160 siren wired up. The factory radio is a Delco series 2000 VF display. I did use the 22ga gray dim wire to control back lighting on the Galls siren and that works well. So I have a 22ga yellow wire that is hot when the head/park lamps are on, a purple/white 22ga wire that goes to the A/C control that should have a PWM signal, and the 22ga gray dim wire connected to the rheostat with a variable voltage. Except for me using the gray wire on the siren these are all open, left cut from the harness and not wired to anything. I have a delco radio I took out of my junk Roadmaster, I took it apart and wired up the board to see if I could get it to work. Now I only wired the board with 12v hot in run, I left the hot all time power disconnected, someone on Buickforums told me they did the same thing but made sure to have 12v hot and 12v hot in run connected to radio. This shouldn't be the only solution, all I really need is something that can convert analog voltage to digital PWM.
This is what I ordered: have also seen people claim that they have bought aftermarket radios built specifically for GM and this issue, I think maybe by Kenwood, but I couldn't find anything. I think this issue is so outdated that no one really cares anymore. Good luck with this one! Thanks, Chris.

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