Glow Plug Relay

[rabbitman]

D'oah!!  Forgot to time the GP light.. 

My gp's usually stay on about 5 seconds longer than the light. I've never timed it though and it probably changes with coolant temp.

[maxfax]

They time the GP's stay on after the light goes out is varied by temp..  Just haven't timed it in different temps to see how much it changes..   

Blackdogvan, the original Mk2 fast glow also stays on after the engine is started.. When the relay receives a crank signal it's almost like another clock is started..  This amount of on time for the GP's is also varied by coolant temp.. Once again, I haven't timed it to see exactly what happens.. 

I got impatient and just threw the thing on the car..  It seems to work quite well on this application...

[92EcoDiesel Jetta]

There are crude figures with lots of room for inaccuracy.. Using a heat gun and temp gun this is what I got for rough and rounded readings from a MK1 GP temp sensor..  Temp is in Deg F

Temp     Ohms
30         3200
50         1400
100         200
150          80
200          40
250          20


With no temp sensor, the fast glow relay stays on for about 45 seconds..
At 30 it runs for about 25 seconds, 50 it runs about 12 seconds..   Doesn't seem to come on at all much over 70 deg F..  

What accuracy would you say these numbers are? Thanks!

[maxfax]

I'm not sure how accurate those numbers are, I'd say within a few degrees and several ohms pending on the temp...   To give you a better feel for them:

My ohm meter was dead on as it was just calibrated and I did clean the contacts so the resistance should be pretty accurate.. However it was a used temp sensor so I'm sure there is some variance from a new one, and I'm sure new ones vary between batches and manufacturers..  According to the documentation, my temp gun was accurate to +/- 3 degrees F at 1" distance.. It is however well abused so I would suspect that could be more..  I was measuring temp on the surface of the sensor, instead of the air temp so that should help with accuracy..   

[maxfax]

I referenced this thread for coolant temp sensor values, and realized that yet again, I didn't follow up!  Vw GP relay works absolutely dandy on the Olds diesel..   Matter of fact, the car has been sitting for almost 2 months and fired right to life...