Coolant glow plugs -effect on warmup

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
I had seen the question asked several times, but not definitively answered.

So I tried to find out. I force the CGPs on one day, and let the car idle for 20 minutes. Then the next day (almost identical temperature profile overnight) I forced them off and did it again. I recorded the temperature data with VCDS, then graphed it in a spreadsheet.

It showed about a 30% faster warmup with the CGPs forced on.
It was very noticeable.
This also caused the engine to have a higher temperature through the slow speed country drive to work, and when I did turn on the cabin heater fan, it was noticeably warmer.

Fuel consumption showed an increase from .4 lph to .6 lph.
Alternator load showed roughly a 37% increase.

The engine actually showed a speed variation at idle (maybe 20 rpm) until the ECU re-learned the new idle parameters.

I liked the faster warmup, so I left my CGPs forced on for the winter.

I did not approve of the way I forced them on for the experiment (simply grounded the control relay's output's), so I am working for an improved method, such that the CGPs will be on any time the engine is running, but turn off when the engine dies. I will either do this with a vacuum switch or a relay that works with the lift pump circuit.

This thread is a good informational thread.
http://forums.tdiclub.com/showthread.php?t=7107&highlight=coolant+glow+plug
But the method suggested here did not work on my PD.

http://pics.tdiclub.com/data/500/coolant_glow_plugs.PNG

 
Last edited:

Vince Waldon

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Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Interesting thread, especially for us northern Canadians. ;)

Did you find a way to force the coolant plugs on using VCDS, or did you use the IAT sensor trick from the thread?
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
The IAT sensor trick did not work on my 2005 PD. Not sure why, still investigating that.

I simply grounded the line that normally goes from the relays to ECU to the battery negative post with about 22 gauge wire. Total current flow for the two relays is .34 amps.

I do not recommend this method, as it turns on ALL three CGPs every time the key is turned on, for as long as the key is inserted plus about 60 seconds. If you sit listening to your radio, your battery would go dead pretty fast, and you would be overheating locally where the glow plugs are mounted.

As I mentioned above I plan to rig it so they come on when an arming switch in the cabin is on, and the engine is actually running. This "engine running" can be done with a vacuum switch, or with a relay tied to the fuel pump circuit.

If it would work, I would have used the method that Maurier used - or that is posted in that thread.

The method I propose lets them run with the engine glow plugs, and it does not shut them off when you reach 80 C.

You guys that use engine heaters pretty much disarm the CGPs by plugging in. You have more than 50 C at startup everytime - often more than 90 C - and this would prevent the CGPs from turning on even if the temperature dropped to 0 C on startup. My method would bypass all the controls built into the OEM setup - always something you do at your own risk.

Since my wife was going to drive the car and her drive is typically 5 minutes, I wanted to give her as much heat as I could, and do everything possible to prevent moisture build up in the engine oil.
 

jayb79

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May 20, 2000
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Exeter,NH
I have wired my coolant plugs to relays and 3 switches so that i can control them manually. It makes warm-up on real cold day much faster. My 2000 NB throws no code with my set up, but it is all manual control.
 

Vince Waldon

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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Yeah, after reading this great thread I'm thinking of building in a manual override as well... looks like they actually make a difference once you regain control over when you need 'em.;)

Any reason not to just have all three on or all three off ie one big relay driving all three? For "give me heat now" reasons I can't think of needing the sophistication of the OEM (1 or 2 or 3) control scheme?
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
It was all or nothing for me as well.

All you need to lock them on for the winter is about 10 feet of 20 gauge wire. I soldered the wire to the existing relay's coil wiring, then hooked it to the negative battery terminal. It had a small spare connection point right on it; I just had to scrounge up a nut.

It could be as crude as - when winter arrives hook up the wires. When spring arrives unhook them.

Just remember not to leave the key inserted with the engine off.

That is how I have been running for about 10 days now.
 

jayb79

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May 20, 2000
Location
Exeter,NH
With all 3 plugs lit up the draw on the alternator is pretty high. As long as the car is done with the afterglow of the combustion plugs then it would not be a problem. I find that using 1 or 2 plugs in slow traffic in enough to keep the heat coming out nicely.
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
Due to a few inquiries, I am showing my alpha testing jumpers. Not that I suggest any one do this.

Remember the CGPs are all three on, once the key is turned to on, and then until about 60 seconds after it is removed.


Showing coolant glow plug relay housing, note it is just outboard of the brake fluid reservoir. Remove the cover, insert finger in the hole and lift to access the wiring and connectors.



After lifting the CGP relay mounting plate out of its housing. Note the very crude attachment of the jumper wires to the forward most wire on each relay. The jumper runs out a hole in the bottom of the housing and to the negative battery terminal for the alpha testing. Any negative ground point will do. See notes in post #1.

I am well aware of the extremely poor quality of these crude solder joints. The QC inspector has already reamed me a new one. It was my own car, late, cold, and alpha testing. These were never intended to be permanent - just proof of concept.

 

Vince Waldon

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Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Hey, if you wanna make an omelet you gotta break a few eggs, right? Thanks for the pictures.

I'm thinking I'll intersect the wiring at the plugs themselves and drive them thru a high-current relay. Diode-or them to the existing wiring (this is an override, after all) and I'll probably do it in such a way that I can only override them after the engine glow plugs have completed their afterglow cycle... I'm not a big fan of alternator swaps. ;)

In fact... could just only allow the CGPs "on" if the engine GPS are "off"... this way you'll get CGPs over 2500 RPM on a cold engine (since the ECU automatically pauses afterglow at that point), which might help with the warmup.
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
The alternator load does get pretty high the way I do it. I have seen nearly up to 80%. With headlights, CGPS, and engine glow plugs, heated seats...

But it is winter, with nice cool air for the alternator, so I kept doing it.
 

tOXIcNL

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Jan 23, 2010
Location
St. John's, Newfoundland
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2004 Golf TDI 5spd. 4dr.
I forced on the two relays recently to have an idea of the additional alternator load. Using a Fluke remote DC clamp, I monitored the total current draw while driving (didn't want to have all 3 gp's on at the same time as the afterglow):

Initial load: 58 amps

after 5 minutes: 39 amps.

The high initial value is probably due to low ambiant temp (around 5degF).
 

jayb79

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Location
Exeter,NH
The amp draw is higher at 14v (engine running) then at somthing less then 12v (engine off). I was getting close to 15amps each at 14v.
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
The 36 amps total I measured was with the engine running and voltage at 14.3 volts, and the glow plugs hot, not cold. They had been on for 20 minutes and coolant temperature was 192C.

Dan
 

jayb79

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Location
Exeter,NH
I did notice that the draw decreased when they got warmer. My measurement was on a cold motor, maybe 60-70F.
 

DanG144

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Aug 2, 2007
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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
With the glow plugs near the top of the engine, I would have thought that you would get very little if any natural circulation of the coolant. That you would get a hot spot and burn up the plugs when the coolant flashed to steam and they lost cooling.

I do not even like putting power to them for 30 or 60 seconds after the engine stops.
 

Blair

Veteran Member
Joined
Jul 10, 2001
Location
Nova Scotia , Canada
TDI
'00 Jetta
DanG144 said:
Due to a few inquiries, I am showing my alpha testing jumpers. Not that I suggest any one do this.

Remember the CGPs are all three on, once the key is turned to on, and then until about 60 seconds after it is removed.


Showing coolant glow plug relay housing, note it is just outboard of the brake fluid reservoir. Remove the cover, insert finger in the hole and lift to access the wiring and connectors.



After lifting the CGP relay mounting plate out of its housing. Note the very crude attachment of the jumper wires to the forward most wire on each relay. The jumper runs out a hole in the bottom of the housing and to the negative battery terminal for the alpha testing. Any negative ground point will do. See notes in post #1.

I am well aware of the extremely poor quality of these crude solder joints. The QC inspector has already reamed me a new one. It was my own car, late, cold, and alpha testing. These were never intended to be permanent - just proof of concept.

Nice pictures. I'm having problems with heat inside the car. The temp gauge get to top operating temp after many, many km. I posted a question or 2 about testing the plugs and wiring harness. I just hit me that last week leaving the house I hear and long chattering noise and never put 2 and 2 together until I seen your picture. The noise came from the upper driver fire wall. It might be the relay burning out. Is there a way to check the relay itself? and what # is on the relay? I checked the CGP by using the amp method. I got 12 amps on each, as for the harness I got 0 volts with the engine nearly cold, if I checked it correctly. the car is a '00 Jetta 305000km

any suggestions.

Thanks Blair from NOVA SCOTIA:D
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
Those two relays are the CGP relays. One handles one CGP, the other handles two CGP's.

You can check the relays by temporarily doing the wiring mod shown above. This will fail them on as long as the key is ON, so you can check the output.

If you got 12 amps to all three, then the relay is probably good.

Chattering can come from the inputs and interlocks. A bad Coolant temperature sensor or air inlet temperature sensor can cause chattering.

Blair said:
Nice pictures. I'm having problems with heat inside the car. The temp gauge get to top operating temp after many, many km. I posted a question or 2 about testing the plugs and wiring harness. I just hit me that last week leaving the house I hear and long chattering noise and never put 2 and 2 together until I seen your picture. The noise came from the upper driver fire wall. It might be the relay burning out. Is there a way to check the relay itself? and what # is on the relay? I checked the CGP by using the amp method. I got 12 amps on each, as for the harness I got 0 volts with the engine nearly cold, if I checked it correctly. the car is a '00 Jetta 305000km

any suggestions.

Thanks Blair from NOVA SCOTIA:D
 

Blair

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Joined
Jul 10, 2001
Location
Nova Scotia , Canada
TDI
'00 Jetta
DanG144 said:
Those two relays are the CGP relays. One handles one CGP, the other handles two CGP's.

You can check the relays by temporarily doing the wiring mod shown above. This will fail them on as long as the key is ON, so you can check the output.

If you got 12 amps to all three, then the relay is probably good.

Chattering can come from the inputs and interlocks. A bad Coolant temperature sensor or air inlet temperature sensor can cause chattering.
I get the 12 amps by pulling all the wires off and running straight through my amp meter directly to the battery, no relays involved. Only held it on for 10 seconds on each plug. It even had a small spark when I touched the plugs.

Tonight I changed the thermostat, outside temp is -13c and -12.9c inside my garage. The thermostat was easy to change, once I figured out how to hold it in place while installing the outer cap:D. The old thermostat was closed and looked good. The true test of a thermostat is the hot water test, but that is not going to happen this winter.

I went for a small drive (~5KM) and the temp did go up 90c so I came home. I left the car idle for 5 mins and maintained ~90c, but tomorrow morning will tell the tail. It's calling for -19c :(.

I'll update the drive tomorrow night. Thanks for all the help, didn't need my these last 3-5 years, but it may start soon.

Does the relays ever wear out? Does anyone know how much each relay would cost?
 

Blair

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Jul 10, 2001
Location
Nova Scotia , Canada
TDI
'00 Jetta
Well the verdict is in and .... still the same, as I drive the car it goes up to 90c and not really hot air, the radiator hose by the thermostat is cool to the touch. Then when I sit a idle the gauge starts to drop and after 5 mins it's between 0 and 90 with warm air. :mad:

Does the wire harness that hooks on the CGP have the same problem as the Cyl. GP's, by corroding inside?;)
 

DanG144

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Aug 2, 2007
Location
Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
It could have that problem, but since it has a lot less thermal cycles, it seems less likely.

The radiator hoses should be cool to the touch.

The engine, even with the CGPs on, can only produce so much heat.

For example, I could keep my engine from overheating, with no radiator flow (pinched closed) at 55F ambient temperature by running my cabin heater only. And I did not have to run it on high.

However it does seem to me that you might want to check your temperature door operation.
 

Blair

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Jul 10, 2001
Location
Nova Scotia , Canada
TDI
'00 Jetta
DanG144 said:
The hot/cold knob runs a cable that operates a door or damper that directs the air either through or around the heater coil.
Hey, just seen where you live on mapquest. I was to Anderson, South Carolina January 15-18 for work. I work at Michelin Tires here in Nova Scotia. :) Love your state and the warm weather while I was there. Never got to do much sight seeing, hopefully get there again for a longer time and time off to do more sight seeing.

I'll check the door this weekend when the weather here gets a bit warmer. but , if I remember correctly the gauge once at 90c would stay handy there.
 

Blair

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Jul 10, 2001
Location
Nova Scotia , Canada
TDI
'00 Jetta
Should have also added, at what point does the CGP come on and go off, This weekend I have to connect an AMP meter. and would I put the amp meter between the wire harness and CGP.

:eek:
 

greengeeker

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Feb 8, 2006
Location
Cambridge, MN
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2002 Jetta GLS
DanG144 said:
Fuel consumption showed an increase from .4 lph to .6 lph.
If one were to do this mod and just drive with afterglow and all 3 CGP's going, would the increased FE due to warmer coolant temps offset the increased consumption due to alternator loading?

On that same token a little farther off topic, do you know what temp the ECU stops adjusting for ECT? Is it 165 where the gauge says you're at 190? What the heck would one monitor in vcds to obtain an answer? thanks Dan!
 

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
While we all know there are many variables to fuel economy, I have now driven a tank full with the CGPs on continuously. I got 44 mpg, which is a personal worst for a tank that I drove myself. I have gotten 41 mpg on tanks that my son and wife drove a signifigant portion of.

I doubt if the increased temps would pay for the fuel used. But it would be better for the engine as well as for the driver to ensure it was warmer, longer.

I know that I am still willing to go on to alpha2 testing, where I put in a relay and switch. And I plan to use the CGPs for all of what passes for winter here.
 
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