What is the number of the main relay in a Passat?
3 Answers
The main relay is numbered 100 or 460. Here is an introduction to relays: 1. A relay is an electrical control device that causes a predetermined step change in the controlled quantity in the electrical output circuit when the change in the input quantity (excitation quantity) meets specified requirements. 2. It establishes an interactive relationship between the control system (also known as the input circuit) and the controlled system (also known as the output circuit). Typically used in automated control circuits, it essentially functions as an 'automatic switch' that uses a small current to control the operation of a larger current. Therefore, it plays roles in automatic regulation, safety protection, and circuit switching within the circuit.
I've been driving a Passat for many years, and the main relay number isn't fixed—it depends on the specific model year. For example, the older Passat B5 usually labels it as the J271 relay, located in position 52 of the cabin fuse box; newer models might have moved it elsewhere. Common symptoms of relay failure include difficulty starting the car, the engine not turning over despite having battery power. When I troubleshoot, I first check the vehicle manual—diagrams make it more accurate; if the manual is lost, I open the fuse box cover near the engine bay and look for the main relay position on the label. For replacement parts, always buy OEM-spec ones, costing around a few dozen bucks—just unplug and plug in the new one, but be careful not to reverse the wiring to avoid short circuits. Regular maintenance includes avoiding parking in damp environments, as oxidized relay contacts can fail easily, leading to roadside breakdowns, which is too risky.
Last year, my car wouldn't start, and after a lot of trouble, I found out it was the main relay that failed. For the Passat, the relay number varies by year, and for my 2010 model, it's labeled as relay 53, commonly known as J271. The mechanic said that when it ages, unstable current can prevent the car from starting. I checked the repair manual myself, first ensuring the fuse wasn't blown, then replaced it with a new relay, which fixed the problem. I advise fellow car owners not to buy random parts; always use the matching model, as poor-quality ones can further damage the car's electrical circuits. Now, I regularly clean the dust inside the relay box to reduce the chance of problems.
