Description

Audi 80 2005 Wiring Diagram – Factory Electrical Schematics for the 1990 Model

If you are chasing an electrical gremlin in a 1990 Audi 80 and you have been relying on a cheap aftermarket diagram that has wires colored wrong or missing relays, you already know the pain. I have seen more burned fuses from guesswork than from actual shorts. This Audi 80 2005 Wiring Diagram is the real deal – a 15‑page Mitchell OEM reproduction that shows you exactly how the factory wired the cooling fan, defoggers, horn, memory systems, and power door locks. No reprints, no third‑party interpretation. Just the original schematic data from 2005 for the 1990 model year.

Cooling Fan Circuit: Diagnosing Overheating Issues

On page 1 you get the full cooling fan circuit – high‑speed relay, after‑run control unit, thermo switches, and the A/C high‑pressure switch. If your fan runs all the time or never kicks on, you trace it through the fuses (20‑30A) and the G201 ground behind the left side of the dash. The diagram labels every wire color: RED/BRN, GRN/BLK, BLU. No guessing. I have seen DIY guys replace a radiator fan only to find a bad relay – this page stops that waste of $200.

Defoggers and Horn Circuits: Tracing Power and Grounds

The defogger circuit on page 2 shows the rear window heat element, driver and passenger mirror heaters, and the switch. Fuse 16 at 30A, hot in run. The horn circuit on page 3 is even simpler: dual horn relay, fuse 3 at 25A, and the horn button ground. But here is the killer – if you rely on a generic manual, you might not see that the horn relay gets power from the fuse/relay panel on the left side of the engine compartment. This diagram shows it. Use it and you save an hour of probing with a test light.

Memory Systems and Power Door Locks: Factory Wiring Logic

Memory systems (page 4) and power door locks (page 5) can be a nightmare without the correct pinouts. The manual covers the wiring from the fuse/relay panel to the interior lights system, rear antenna amplifier, and instrument cluster. For power locks, it tracks the circuit through the relay and door actuators. If you are swapping a door harness or troubleshooting a lock that only works sometimes, the diagram shows you the exact wire paths and connector locations.

Why Factory Wiring Diagrams Beat Aftermarket

I have seen aftermarket diagrams that list the wrong fuse size or omit the relay coil ground. This document is a direct scan from Mitchell Repair Information Company – the same data that shops pay for. The 15 pages are crisp, the wire colors match the car, and the circuit numbers (like G202 behind left side of dash) match the actual hardware. If you need to check Automotive Wiring fundamentals, that is fine, but for an Audi 80, start here. Do not rely on a half‑page summary from a forum.

Who Needs This Manual?

If you are a DIY home garage guy working on a 1990 Audi 80 and you want to fix a non‑working defogger, a fan that stays on, or a door lock that clicks but does not move – this is your wiring diagram. Professional mechanics will also use it to verify circuits before ordering parts. The manual assumes you know how to read a schematic (fuse numbers, relay pins, ground locations), but it gives you everything the factory intended. Pair it with a proper Audi 80 1995 Workshop Manual – Suspension, ABS, Self-Diagnosis for mechanical jobs, or the Audi 80 1996 Workshop Manual – Factory Electrical System Guide for later years. For the 01E gearbox specs, grab the Audi 80 1997 Workshop Manual – Factory Specs for 01E Gearbox.

Does this wiring diagram cover the interior lights and radio?

Yes. The interior lights system is referenced in the memory systems circuit on page 4. The rear antenna amplifier is also shown.

What about the engine management – does it include the fuel injection wiring?

No. This 15-page manual covers only the body electrical systems: cooling fan, defoggers, horn, memory systems, and power door locks. For engine management, you need the main workshop manual. Check the Automotive Wiring resources for general electrical theory, but for engine control wiring you need a different document.

Every circuit in this manual comes from the OEM data published in 2005. It is the same schematic a dealer tech would have used. If you want to stop chasing ghosts in your 1990 Audi 80, stop piecing together forum screenshots. Access the Factory Manual and get the exact wire colors, fuse ratings, and relay locations. You will save more time than the $15 cost.