2001 jetta glow plugs only work when below 40 degrees
Our jetta glow plug lamp comes on for a second and then turns off when outside temp is above fourty. I am thinking it is one of three temp senders at the thermostat, but can not find anywhere with the senders I have. All of the parts houses have four pin senders, but not the one male senders like our jetta has. Any suggestions?
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I drive a 2004 F-350 with a 6.0l. 5 glow plugs are out, have to start on ether when temp is below 40 deg F. CAUTION turn key on, wait for glow plug light to go out, spray approx 3 seconds, start. Should crank about 3-4 seconds then fire off. I work on heavy trucks by trade, mainly roadside service work.
Run the plug's a couple time's instead of one. For an example on my work truck I run the plugs 3-5 even more depending the outside temp. Also I don't crank more then 20 second's. This work's even in extreme temp's such as -25F. And if you don't have the patience for this there's always starting fluid.
The glow plugs work in direct relation to the engine block temp. The relay for the glow plugs is obviously reading the wrong temp, that's why they turn back off. It's most likely that the temp sensor is bad, but trace the wires back and make sure there are no breaks in the insulation and they are well connected at the plug-ins. I have seen a lot of wires at the connector look good but fall off as soon as you touch them.
If the temp sensor is the same on for your your dash, then borrow a heat sensing gun and double check it against the guage. I have seen them read wrong by as much as up to 20 degrees. If the sensor reads rught and feeds both the guage and the glow plugs, then the problem would be either the wire harness or the glow plug relay. Hope this helps.
Before you invest in a long drawn out Glow Plug replacement etc. A little known issue occurs on the ALH TDI engines. The temperature sensor sending unit. A small blue module that plugs into the coolant hose assembly will cause a P error on the glow plugs that is nothing to do with the glow plugs at all. The part fails and sends a temp error to the engine computer. I tested all the coolant glow plugs, engine glow plugs and glow plug harness and all worked fine. One of the test procedures for the glow plugs is to undo this sensor that will force the glow plugs to come on no matter what temperature. This confirmed my GP system was functional and the sensor was bad. I purchased the part from local VW dealer for $33 US and installed and it is fine. Dependent on your model it can be square or round. The link to this part for your car is http://www.partsgeek.com/catalog/1997/volkswagen/jetta/body_electrical/water_temperature_sender.html
Be sure to have VW Pentosin coolant on hand to refill coolant system as you will lose quite a bit when removing this part. It is located slightly behind the coolant glow plug assembly.. This is the round ones not the ones on the engine block at top.
Be sure that when you replace it you put in a new rubber gasket seal.. its a round rubber seal that should come with your new part. Dont reuse the old one or you will have a leak.
There is a c-clip that holds this in the hole you slide that clip off and wiggle the sensor out. Coolant will run out of the hole, so do this outside. The sensor is easily pulled out. You will need to insert the new part in teh same hole with new rubber gasket and replace c clip. Then plug in wiring harness and you should be good to go.
Depending where you live if the temp. is over 45 degrees F the glow plugs shouldn't be needed for the engine to start. Have you ever had the check engine light come on? Your problem is probably not in the glow plugs.
glow plug relay is marked #180 on the housing.
in 0 to 11 degrees they have a starting prob were the glow plugs go on and off very quickly.need VAG.com to exstend glow plug timing.
to test glow plugs disconeect ect turn key on plugs should draw 15 amps each 60 amps all together.if you dont have amp meter use test light.