Manual Glow Plug Switch

Update: Some interesting things here. I solved my issue with common grounds causing the instrument cluster going crazy. I did this by grounding the voltage regulator on the drivers side fender. I also decided to not ground out the switch light. I'll just remember which way is on.

I did not install the second diode. Well, I tried, but it turns out that with the diode causes a voltage drop, from 4.98V to 4.3V, which it turns out is enough to not make the GP relay kick on. It does not seem to be an issue though.

Which brings me to the interesting part. With the key out of the ignition, and the manual switch turned on, the ST line reads 4.98V. Exactly as it should. However, the glow plugs will not turn on because the ignition switch is not on, which makes sense. So, with the ignition switch on and the manual switch off, there is no voltage on the ST line. But, with the ignition on and the manual switch on, there is not 4.98V as there is when the ignition off, but rather there is 11.06V....I don't understand that at all. I tested the ground from the regulator with both switches on and it had 7V. I am somewhat confused.

None the less, the manual system seems to work with the exception of the CEL that occurs. So does anyone have any ideas on how I could pulse my signal to the GP relay instead of a constant signal. I suppose the thing would be to send the pulse at a rate at which is less than the ECU "time out".

A ground is 0V. If you are seeing 7V on the regulator ground pin, it is not grounded. With 5V out and ignition off, the regulator is working properly. With ignition and manual switches on 7V on the ground pin suggests to me that the ground path is through one of the switches. Is it possible the ground for the regulator is through the manual switch light circuit? Try grounding the regulator to another place, or tap into a brown wire under the dash.

Paul

I meant to say that I got 7V at the end of the ground wire rather than the pin itself. So in this case, I put 12V in the regulator, I see 5V on the ST line, and with the ground wire connected to my multimeter (not to the car) I get 7V, which I think is how it is supposed to be. Each of the lines in the diagram is an actual physical wire, so it is not possible that this system is connected to any part of any other system with the exception of where it ties into the GP system. Like I said, the interesting thing is that with the ignition off I get my intended 5V on that ST line but no voltage at the GPs. But when the ignition on and with the manual switch on, I get 12V at the GPs and 11V at the ST line. For what it is worth, on the opposite side of that diode (the ECU side), I get no voltage in any circumstance.

I added the ignition switch to this diagram towards the bottom. I don't have the actual diagram, but this is my basic and simplified understanding. I can totally see how I could get 5V on the ST line with the ignition off, but not have voltage at the plugs, also because the ignition is off. Otherwise the GPs would be on all the time! But I still fail to see where I am getting 11V with the ignition on (and 0V with the ignition on and the manual switch off). I just don't get where the extra voltage come from, unless for some reason the voltage regulator starts to not work when the ignition is on...

Maybe this will help. VW has a .pdf that describes the 2.0 engine, including the glow plug system (see page 35):

http://www.volkspage.net/technik/ssp/ssp/SSP_316.pdf

Notice that a low level signal energizes the glow plugs and a high level signal turns them off. So one thing to test is, "Does grounding the ST pin energize the glow plugs?"

Also note that on their diagram, they use a green line to indicate the control signal from the ECU and a blue line to indicate the diagnosis signal to the ECU. On the 2003 ALH glow plug module, the ST wire is blue (with a black stripe) and the D1 wire is green (with a black stripe). So it's possible that if you ground the D1 wire, you'll get power to the glow plugs. Or this might be just a big coincidence.

That is interesting. They do the same thing on the 1.9PD brochure (pg.53), but the VE one is a little less clear (pg.26). I think the system changed on the ALH engines somewhere around 2002 though.

http://www.myarchive.us/richc/VW_TDI_with_PumpeDuse.pdf
http://www.haywood-sullivan.com/vanagon/TDI/tdi-technik-eng.pdf

I outright called Bosch (up in Michigan) and spoke with a guy named Jim. He deals with all the VW electrical systems, and listening to him talk about this stuff is like watching a master at his craft. He confirmed that the ST line sends diagnostic information to the ECU and that the D1 line is used to signal the plugs to go on.

We spend 20 minutes talking about the VW system including the ECU. He made some interesting points. First of all, if the CTS is bad the ecu will default to the air temp. Not sure what that means for me, but interesting none the less. But, he says that the issue is likely related to the wiring for the CTS. In a nut shell, the CTS is a (I am making these words up) a reverse output sensor. That is, the hotter the coolant temp is, the lower it will output to the ECU. As the temp lowers, the Sensor will ground out some of that signal. So, with the CTS unplugged the ECU (he didn't explain how) will get all 5V from the sensor wiring and hence think it is really really cold. Or something like that....

Being the case that my glow plugs work in post glow and in output tests, it seems that the plugs, harness, relay, and likely the ECU are alright on the output side of things. According to him, the issue is likely related to the CTS circuit. As he put it, a problem with the wiring, grounds, or output voltage form the ECU would cause the ECU to not turn on the plugs, but not necessarily put out any sort of code saying something is wrong. So I guess its time to look into that area. IF I don't find anything at least I now know that the D1 line is the one that should be tapped into if I want to try manual again.

I was up-to-date on this thread through page 3 but I thought about something last night when I was falling asleep...I've actually thought about doing this myself:

What if you cut one of the wires to the CTS and ran some wires from each end to a switch in the cabin of the vehicle. Under normal operation the switch would be "on" meaning the CTS is plugged in and properly sending its signal to the ECU, BUT whenever it's really cold outside and you need to start the car, you get in, turn the switch "off" to simulate a missing or faulty CTS, the ECU defaults to -10 degrees or whatever, you let the plugs stay on for like 20 seconds, then flip the switch back to "on" and start the car.

I think that is the best and easiest "manual" glow plug switch. But it's pretty safe because you won't burn out the plugs or anything because they'll still ultimately be controlled by the ECU, you're just tricking the car into thinking it's WAY colder than it is, then before you crank it, you correct that false signal and roll on.

What do you guys think?!

PS_That would be a STUPID easy installation.

...and I just realized that even with your CTS unplugged your glow plugs don't come on correctly...sorry!

Well it's a GREAT idea for me at least :0)

Yes that would work if the CTS worked. It may work for you, but I would say this, by doing so you will get a CEL every single time you hit that switch. The method described here of putting 5V on the control line to the glow plug controller (the line going to pin D1, as we now know) should work and at this point (because nobody has tried it on that pin yet) there is a decent chance of not causing a CEL.

What is the problem with yours? I have been at this so long I feel as though I know the way to fix all the glow plug system issues excluding mine...

freakwithracket said:

Yes that would work if the CTS worked. It may work for you, but I would say this, by doing so you will get a CEL every single time you hit that switch. The method described here of putting 5V on the control line to the glow plug controller (the line going to pin D1, as we now know) should work and at this point (because nobody has tried it on that pin yet) there is a decent chance of not causing a CEL.

Click to expand...

Well I don't think it would trigger the CEL if you turned the switch back before cranking the vehicle. In fact I'm 99% sure that if it's correct at and after start up that the CEL won't be triggered.

freakwithracket said:

What is the problem with yours? I have been at this so long I feel as though I know the way to fix all the glow plug system issues excluding mine...

Click to expand...

Great question! My car starts fantastically in warm to moderate weather but once it gets 40ish and it sits overnight it has a rough time starting. The glow plug relay, harness, and plugs are all good to go and if I unplug the CTS and let the plugs actually come on then the car starts fantastically. So people say "CTS problem" well I replaced the clearly faulty black one I had 6 months ago with an aftermarket green one which corrected the completely wrong readings but once the cold start issues surfaced I replaced the aftermarket green with a VW green one and the problem persists. I really just feel that my glow plugs don't come on at all or maybe not enough when it's 30-40 degrees. Everyone on here says that's too warm to need the glow plugs but I feel like mine needs them. My timing is right on the very top line of the advanced which should help with cold starts but who knows. The only thing I've found which as helped is to flip my EVRY mod switch, thus increasing fuel injection, this helps greatly with cold starts.

Even though my old harness seemed fine and I was getting 12v at each leg I went ahead and replaced it this past weekend and also cleaned up my battery contacts (they weren't really dirty but now they're nice and shiny). Unfortunately, it's a bit too warm to gauge if this has helped, it's only getting about 45 overnight here.

So what do you think about all that?

I think there is something else wrong with your car and you are barking up the wrong tree. Glow plugs just are not needed in 30-40*F weather.

Do you have VCDS?

I don't know about that. The problem is that for the glow plugs to work at all the key needs to be in the on position, otherwise the 12V from the battery can't make it to the GP relay. So for any of this to work you need the key to on. Once that happens the ECU is up and running, that is of course how it determines temp. and everything else. Once the ECU is running it will immediately see that the CTS is "unplugged" and a CEL will trigger regardless of if you crank the engine or not. I am positive of it. Go outside and unplug the CTS with the key in the on position (remember you need this for the Gp relay to get 12V from the battery) and then plug it back in before starting. You should get a code.

As far as your problem goes, you can go in with a VAG-COM and increase the IQ to where it injects more fuel at idle instead of doing the every mod all the time. You can also go in and change the adaptation value for the glow plugs and make them come on at high temp.

turbocharged798 said:

I think there is something else wrong with your car and you are barking up the wrong tree. Glow plugs just are not needed in 30-40*F weather.

Do you have VCDS?

Click to expand...

I will have access to VCDS for a few days in December (my father-in-laws) and I'll be in the mountains of NC where it should be below freezing nightly.

What do you suggest I check? I plan on increasing my IQ a bit (if memory serves I set it around 5) back to 3.5ish. Outside of IQ and timing I don't know what to check. I am planning on checking, first thing in the morning before I've cranked the car, to see if the intake air temperature, coolant temperature, and fuel temperature are all very close to one another. Some of my research as lead me to believe that it's possible I still have a fault CTS or my fuel temperature sensor in my injection pump is faulty. I guess I won't know until I get a hold of the VCDS. Good news is he'll let me borrow it if I need to and I can ship it to him when I'm done with it if a few days just isn't enough to figure it out.

Thanks guys!

freakwithracket said:

I don't know about that. The problem is that for the glow plugs to work at all the key needs to be in the on position, otherwise the 12V from the battery can't make it to the GP relay. So for any of this to work you need the key to on. Once that happens the ECU is up and running, that is of course how it determines temp. and everything else. Once the ECU is running it will immediately see that the CTS is "unplugged" and a CEL will trigger regardless of if you crank the engine or not. I am positive of it. Go outside and unplug the CTS with the key in the on position (remember you need this for the Gp relay to get 12V from the battery) and then plug it back in before starting. You should get a code.

As far as your problem goes, you can go in with a VAG-COM and increase the IQ to where it injects more fuel at idle instead of doing the every mod all the time. You can also go in and change the adaptation value for the glow plugs and make them come on at high temp.

Click to expand...

Truth.

I suppose you could cycle the ignition after the plugs run and you flip the switch back, but I'd rather just figure out why it won't crank well in 40 degree weather.

Did a test on the CTS connector:

Pin 1: 5.67V
Pin 3: 5.07V
Pin 2: 12.38V
Pin 4: 0V

Based upon the wiring diagram, pins 3 and 4 connect to the ECU. So 5V on pin 3 and 0V on pin 4 makes sense given the connctor was off the CTS. But what about pins 1 and 2, especially pin 2 with its 12V??

freakwithracket said:

Based upon the wiring diagram, pins 3 and 4 connect to the ECU. So 5V on pin 3 and 0V on pin 4 makes sense given the connctor was off the CTS. But what about pins 1 and 2, especially pin 2 with its 12V??

Click to expand...

Pins 1 and 2 control the coolant temp gauge in the cluster. Pin 1 goes straight to the cluster. Pin 2 goes to "sensor ground", which is a common ground point for various sensors such as the fuel level and coolant level sensors. It's unclear whether "sensor ground" is connected to any actual ground point in the car.

freakwithracket said:

Once the ECU is running it will immediately see that the CTS is "unplugged" and a CEL will trigger regardless of if you crank the engine or not. I am positive of it. Go outside and unplug the CTS with the key in the on position (remember you need this for the Gp relay to get 12V from the battery) and then plug it back in before starting. You should get a code.

Click to expand...

Here's a nice page of information about the CTS:

http://s2central.net/ds_G62.html

If you were to go the route of disconnecting the CTS to simulate a cold engine, it would be better to replace the CTS with a 10K resistor. That would tell the ECU that the coolant temp is about 15 degrees F. and not trigger a CEL.

gmenounos said:

Here's a nice page of information about the CTS:

http://s2central.net/ds_G62.html

If you were to go the route of disconnecting the CTS to simulate a cold engine, it would be better to replace the CTS with a 10K resistor. That would tell the ECU that the coolant temp is about 15 degrees F. and not trigger a CEL.

Click to expand...

I just read that webpage. Did I misread or did it say that if the sensor is unplugged the ECU will default to 80C if the air intake is above 0C, and if the air intake is below 0C it will read that temp for 3 minutes?

I don't understand why there is so much difference in what people say about how this system works. This is for a early 90's Audi S2 though..

freakwithracket said:

I just read that webpage. Did I misread or did it say that if the sensor is unplugged the ECU will default to 80C if the air intake is above 0C, and if the air intake is below 0C it will read that temp for 3 minutes?

I don't understand why there is so much difference in what people say about how this system works. This is for a early 90's Audi S2 though..

Click to expand...

That site is for a total different engine, so I would take any specifics about how the ECU operates with a grain of salt.

Lots of tests and data. I correct myself about the ST line, it is in fact the signal line. The CEL is caused because when 5V was added to that line the relay sent diagnostic information back the to the ECU, the ECU was not expecting it, therefore the CEL.

On to the date: The following info was taken with VAG-COM with the engine at 33.3 C.
In a sitting state with the key turned to the on position, the ST line receives 10.87V from the ECU. 0V on the plugs.

Using an output test in VAG-COM, the ST line shows 6.09V, and the plugs receive 12.39V.

During start up pre-glow period tests with two voltage readers hooked up to the ST line and the GP harness, there is 10.87V on the ST line, and 0V on the plugs both with the sensor plugged and unplugged.

During the Post-Glow period there is 7.05V on the ST line and 13.5V on the plugs.

Back probing the CTS connector while it is plugged in I read 5V on pin 3, but no voltage on pin 4.

The air intake temp reading is flakey, sometimes defaulting to the fuel temp sensor.

That being said, according to the Bosch tech support guy, if the CTS is unplugged the ECU defaults to -40 when the key is in the on position. Once the engine is cranked it goes over to the fuel temp. Mine just goes right to the fuel temp with the key on. I am not sure how it even could have happened, but I get the feeling that somehow the programing on the ECU is messed up, or an individual component...

Here is an idea: the ignition switch. The Bosch guy said that the ECU defaults to the fuel temp as soon as the engine is cranked. I assume that there is some sort of signal that the ECU gets from the ignition switch (perhaps a dumb signal) that informs the ECU to turn off the glow plugs. Perhaps the ignition switch is bad or faulty in such a way that with the key in the on position, there is that signal sent to the ECU. That would make sense, seeing as my ECU is defaulting to the fuel sensor temp with the key in the on position when it should not do that until the engine is cranked..

Holy cow...I have been reading non stop for a few days ..This is the SAME Issue I am having ..* mild weather * 40-60 deg. has a slightly exstended ( first start ) GP test good, GP harness Test good, Scan tool showing live data ..the CTS reads Ambiant Temp...Plugged in or Disconnected.

I'm gonna Try To Check IP timing with my Current Scan tool.

I too ...Thought about installing a Manual GP switch..But much prefer to Find & fix the Issue.

40-60 degree= glow plugs not needed. ECU will not command glow plugs until 30*F or so.

Turbo . I have read that sentence 100 times...But it just doesn't make sence. since cents .If the car starts fine when its 80 deg. outside and then The days its 40-60 deg. outside it has a 4-5 sec. exstended start time ...Obviously it does self adjust to Ambient temp normaly . Extending the Glow time. or else when it was 10Deg. outside it would never start. And to top it off ..Unplugging The CTS and the Temp on Live data does not Change. " everyone post on here it should drop to Below 40" And Trick the ECU into thinking its freezing. Mine still reads ambient temp.This is the issue I am having.

On My Dodge Diesel...It also is Self adjusting GP time to Ambient temps..And will exstend GP time anything under 60 Deg.

Right, but this is not a dodge cummins. If you have problems starting in 40*F weather, GLOW PLUGS ARE NOT THE ISSUE!!! You either have low compression, retarted IP timing, or poorly spraying injectors. Again, keep repeating it because a properly running TDI will not need glow plugs until it gets below freezing to start. Heck, my ALH will fire up in 25*F weather with no glow plugs at all(harness unplugged, a bit rough and smokey) .

If you are unplugging the CTS and the temp the ECU is reading does not change, then you are either unplugging the wrong sensor or there is a wiring problem. The ECU should default to max cold temp(-40*F IIRC) and give you max injection advance and glow plug time.

Coolant temp sensor are also extremely fail prone on these cars and if its sending the ECU the wrong info, all sorts of issues will result.

Turbo. I thank you for your input..I am by far not Trying to be "THAT GUY " who thinks he Knows it all....with that said..I'm with you on the " it has a issue with the CTS reading " I am 100 % sure I am unplugging the correct plug..It is even the supposed updated Green CTS. I'm looking past the Glow plugs ..already stated that in my thread that nobody responded to . I'm looking to Check the IP timing ..Due to the Fact it looks BRAND NEW & has a Very New T-belt ..But I don't know the service date or miles. I asked the Question of ..Does anyone Know If the Latest Autel Scanner From Snap on Will read the IP Timing.If so..Can anyone tell me What group # to Find it in.

freakwithracket said:

Here is an idea: the ignition switch. The Bosch guy said that the ECU defaults to the fuel temp as soon as the engine is cranked. I assume that there is some sort of signal that the ECU gets from the ignition switch (perhaps a dumb signal) that informs the ECU to turn off the glow plugs. Perhaps the ignition switch is bad or faulty in such a way that with the key in the on position, there is that signal sent to the ECU. That would make sense, seeing as my ECU is defaulting to the fuel sensor temp with the key in the on position when it should not do that until the engine is cranked..

Click to expand...

Yeah, back to the ignition switch theory, any support for it?

2001 manual glow plug system

I've been thinking about a manual glow system as well. After reading this discussion, I'm thinking that bypassing the VW glow wiring entirely might be the way to go. If a guy could buy an aftermarket 5V relay and run 5 (6 gauge?) wires from it to the battery and glow plugs individually, it seems like you could operate this system with a push button on the dash (with fuses in the proper places). Then you could push the button and glow the system BEFORE you turned on the ignition. Let off the button and then start the car normally. Correct me if I'm wrong, but it seems like the computer would be unaware of the manual glow plug heating. The other thing I'm uncertain of is whether a 5V relay like I describe above is readily available.

shinkamp

i want to do this to my TDI a quick explanation would be helpful