VagCom Question--->

After doing my own troubleshooting the CEL and no luck, I decided to hit the dealer yesterday. I asked the Service Manager if I could get my CEL code read. After 1.5 hours they came back with "Glow Plug Relay". Next they (she) said they didn't stock a replay and that it was about $150.00. (No, I didn't want to pay $150.00 for the relay when I'd priced it before on the web for $105.00... I think.) The charge to read the codes, $75.00. I don't guess they were too happy about me changing my own timing belt?

So, the question is... I've looked here before for VagCom information, like where to purchase it and couldn't locate it using the Search. What's best, cheapest or whatever?

Looking at the Forums I'm kinda lost. Why are there so many divisions? Makes my head hurt this morning. I hope I didn't make a Boo-Boo my posting here. If I did, Heck I just knew I was going to Screw Up one Day!

My Tdi is in a 1998 Beetle (and yes, it has round tweeters).

Almost forgot. What about the Glow Plug Relay? Has anyone been suscessful repairing one? or the best place to buy one?

Thanks guys!

Mike

[ January 19, 2003, 07:09: Message edited by: MCathcart ]

Go to WWW.Ross-tech.com for the VAG-COM. As for your CEL, I seriously doubt that it is the relay. Check your plugs and harness first before paying $100 bucks for a relay. The plugs burn out after 85,000 - 100,000 miles of use (may be dependent upon where you live and the climate) and harness is a known issue on some vehicles. Glow plugs cost $20 and the harness costs $23. The error code doesn't specify that the relay is bad and it sounds like your dealer is just selling the most expensive item in the circuit.

Do a resisance check of your glow plugs first. Your target is .6 - .9 OHMs. If you get some crazy number like 25 MegOHMs then you have a burned plug.

If the plugs are good then check the harness visually for corrosion at all connectors. The Bentley manual gives a procedure for checking the circuit with a voltage meter at each cylinder also. However, it seems that most diagnostics end with a burned glow plug.

As a last resort you should check the relay. Always start with the simplest component in a circuit when troubleshooting and work your way from there.

If you find a bad plug then save yourself some time and replace all 4 because they're all going to need it soon. Use the same brand of plug for each cylinder also. Don't mix Beru and Bosch. I think they have different internal resistances and will also trip a error code even though your car will start just fine.

Keep us posted on your outcome.

Thanks for the reply FowVay!

I have the Bently manual and studied the relay wiring and pins last night. Question, looking at the Glow Plug Wiring 26/3 97-204 I'm unable to follow the wires to a different page. If you have the manual (and have time) what do the rectangles with a number mean. Bently doesn't say a lot about the relay.

Mike
'98 Tdi, 65k

Don't worry about the wiring to the relay. Pull the harness off the glow plugs (exactly same as sparkplug caps on gasoline engine) and resistance-check the glow plugs. If you find one that's no good, replace one or all depending on odometer. If all are good, replace the "bus bar", which is the pieec that you just unplugged from the glow plugs.

At the bottom of the picture are a row of numbers. Say, 1 to 14. The next page will be 15-28 or whatever. The numbers in the rectangles refer to the numbers at the bottom of the page. So if you follow a line to a rectangle with a number, look along the bottom for that number. You may have to flip pages forward or backward to find it. Circled letters/numbers are described at the bottom of the page.

The relay could have a problem, or the connectors may be dirty/loose, or there may be no problem at all.

Spent some time today troubleshooting the CEL. Started at the glow plugs. 1,2 & 4 read .9 ohm and #3 read 95.0 ohm. Checking voltage to the glow plugs only .186 V DC! Pilled the plug on the coolant sensor and got the same reading. Next pulled the Glow Plug Relay and popped it open. (I'd already checked the contacts once.) Checked the contact again but nothing. Pulled the airfilter box out and checked T2a plug that feeds the glow plugs. Same Low Reading less than 1 volt. Removed the glow plug relay cover and put it back in, carefully poked a piece of plastic into the relay so the contacts would close and got 12.5 volt reading on the meter. Checked the coil inside the relay, and it's good. So, looks like to me the GP relay is BAD and I also found the one glow plug that was weak.

I'll place an order for the parts and let you guys know!

ALso if your car is pushing the five year old mark, check the braded 3.5 mm lines that link the injectors together. Mine were Shot! I couldn't find the 3.5 mm stuff but some 1/8" fuel line worked great!

Mike

You did check for voltage at the harness, with the temp sensor plug removed, within 15 seconds of switching on the ignition key, right???

I tried it with the temp sensor unpluged and with the engine cold. Nothin, less than 1 volt.

Mike