Where is the glow plug relay?

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dieselAndy
Glow Plug
Posts: 2
Joined: Mon Nov 29, 2004 6:54 pm

Where is the glow plug relay?

Post by dieselAndy »

98 Jetta TDI, my check engine light is on and VAG-COM says "glow plug monitoring intermittent". With the arrival of colder weather I'm having starting problems. I've checked the continuity between the glow plug harness and a relay that's on the firewall right above the brake booster and has a 50A fuse on top that always has 12V. There is approx 1000 ohms resistance between one of the lower wires and the glow plug connect at the harness.
Not sure I'm working on the right relay. Can someone confirm?

BTW, all four plugs show 0.5 ohms and I don't get 12V at them when i turn on the key. When I pull the connector off the relay I get 12V on the center pin and 7.5V on the other two pins, is this normal? Anyone have wiring diagram so I can figure out this funky setup?
dieselAndy
Glow Plug
Posts: 2
Joined: Mon Nov 29, 2004 6:54 pm

relay found

Post by dieselAndy »

I can answer my own question.

There are two relays: the one for the coolant glow plugs is on the firewall just above the brake booster, the relay for the cylinder glow plugs is behind the dash on the fuse/relay block and has "180" boldly printed on top. Its fuse is just above, 50A, costs $3.70 at Napa. The fuse is "upstream" of the relay, that is, it's between the power source and the relay. The relay has one central terminal (#30) for incoming juice, and two outgoing terminals (G1/2 and G3/4), for cylinders 1/2 and 3/4. Pull the relay and test for continuity to the glow plug ends of the harness. If you have continuity and 12V coming into terminal #30 of the relay, and all plugs resistance check OK (my situation), then the problem must be the relay or the ECU. I opened my relay, didn't see anything obvious, except it has a microprocessor (curses!). I have purchased a new relay (VW P/N 028 911 253, Bosch 281 003 014) for $40, hope this fixes my problem.
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