Glow Plug Relay going craaazy

[VolkSport]

Hi there, I've been having this problem lately with the glow plug relay switching on and off super fast (about 10-15 times per second) when starting the car when it is warm to hot, but never when it is cold.  I thought the relay must be faulty so I put in all new plugs and a relay on the weekend but to no avail.  The relay will go crazy for a couple seconds or continue doing it for a minute or so with pauses in between.  I am getting concerned as i don't want to ruin my glow plug system and -40 degree weather is approaching quickly!  Has anyone had this happen before or know what may be causing this?  Your help is appreciated.

[burn_your_money]

It sounds like your sensor might be failing, grounding it out and then not. First check to make sure it's making a good solid connection and then try replacing it.

[VolkSport]

That's what I was thinking but was not sure.  Is the sensor the one by cylinder #4 in the head?  I know there is another one but I'm not sure where it is exactly.  The car is an '85 TD w/ solid lifter head incase it makes a difference.

[burn_your_money]

I don't know. There are 2 sensors (in a mk1 anyways) one for the gauge and one for the GP relay. Just get a wiring diagram and match up the wires color's and that should pinpoint the sensor. It will be on the head though, either on the end (cyl 4) or on the front between #2 and #3

[fatmobile]

How do the wires coming from the positive on the battery look?
 On your car they might come from the starter.

[Doug]

Last time I saw a glow relay acting like that it turned out to be defective. The temperature sensor was just fine.

[macsdub]

yea these guys are on it
remove the relay too+look for rust/water on the pins
shake the relay too,ive had them fill up with water from a water leak
you can hear water in them if yo u  shake them+suspect water infiltration