A/C system signals, checking: Notes

Special tools, testers and auxiliary items required 

• Scan Tool (ST) V.A.G 1551/1552 with cable V.A.G 1551/3
• Test box V.A.G 1598/22 (through my 1999)
• Test box V.A.G 1598/31 (from my 2000)
• Digital multimeter US 1119 (Fluke 83 or equivalent)

• Adapter set V.A.G 1594
• Wiring diagram