In-Vent Auxillary Heater Project (warning: picture heavy)

TDIFan1989

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Nov 28, 2013
Location
Toronto
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2000 Mk4 Jetta TDI (Black)
I know a bunch of folks have complained about the lack of heat available on our vehicles (diesels) due to cold weather. I just completed a project whereby I installed a 300 watt 12 volt heater directly into my cars duct work with a toggle switch. Here's some photos to check out. Approx cost of the project was: $30 heater, $5 wire, $10 toggle switch and $5 red gasket silicone so ~$50. Took me about 3 hours to complete.


Here's the stock car heater. It comes with a 12 volt set up. Those switches both control one of two (150 watt) heater cores and both link to the common fan






This gives a more in depth look at the wiring inside the fan
I ended up taking the fan off. Tried to desolder the negative terminal but that never worked out.




And more wiring from another angle



Fan removed as well as the plastic deflector from the front reduced depth to about 2.5 inches, I further trimmed the box away to make it flatter and thinner. Final measurement was 1.5" thick.



After removing the glove box, I ran a few wires from the switch to the underside panel of the blower motor. Figured it was best to have it closest downstream of the blower motor to protect the blower motor from anything adverse. I used a self taping screw for the negative terminal to save on wiring. I ended up running 2 wires because it was easier to connect to the 2 positive terminals on the heater core that way (plus the wire was 60 percent off)






This is what the heater core looked after I did all the reductions. I did not keep the switch provided for the heater in the design for my vehicle




This is the newly installed heater core, as you can see, it is just past the blower motor housing so it is being directly blown unto by the stock assembly. I secured it into place using red gasket silicone as the temperatures might get higher than what black gasket silicone would withstand





This is the toggle switch I used for the project, it is rated for 30 amps and has a Red LED glowing when it's switched on.




I connected the power to the 75A terminal stting underneath the driver side connection points. This particular terminal does not get power unless the ignition is switched on (thereby eliminating accidental drain when the car is off). There is a fuse holder and a 30 amp fuse to protect the circuitry.





Finally, the red illuminated switch indicating everything went together properly.







I did test the auxiliary heater and it does work to give off some amount of heat immediately after starting the car. I will have to wait until the colder weather comes around to show it in action, preferably via video.

Enjoy!
 

csstevej

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vtpsd

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Vermont
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03 jsw TDI, audi 90 AHU swap
good idea, i am damn chilly for the first 5-10 minutes of my commute!
 

belome

Top Post Dawg
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Location
Mid MI
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2002 Jetta GLS TDI 5-speed
I think it is a great idea in theory, but I'm curious to see how much heat 300 watts can throw outl.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
I tried something similar in my air cooled dubs, and found them to be almost worthless.

I still have one of them. I also had one I used to plug into the 12v port in my diesel F350 to aim at the windshield, it would de ice a small 6 inch square eventually.

It is essentially the same idea the newer VAG cars already have, only they have a much greater wattage (and are likely not cheap Chinese materials that melt after a few times being used).

Let us know how it goes, though. I would also like to know what all you did BEFORE this [rather extensive] modification to insure the car is working as best it can as is. Because I know a lot of the ALH/BEW manual cars' coolant heater plugs are long since dead, or the connectors are so bad they no longer make good contact, and people have no idea. When I got my Golf, all three were dead.
 
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Chris B

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Joined
Oct 23, 2001
Location
N. central Illinois
TDI
2002 Jetta Wagon 5 spd
Because I know a lot of the ALH/BEW manual cars' coolant heater plugs are long since dead, or the connectors are so bad they no longer make good contact, and people have no idea. When I got my Golf, all three were dead.
That's a good point, Oilhammer. I've never given mine a second thought, but with winter rapidly approaching I appreciate every bit of heat I can get. I guess after 310K miles and 15 winters, I should probably have a look at mine.

Aside from continuity, what is the criteria for testing? At what temperature should they activate to verify they are getting power?

Thanks!

Chris
 

pdq import repair

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Nov 6, 2016
Location
idaho
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09 Jetta
I think retrofitting a mk5 PTC heater would be more effective. They are larger and more wattage. I have a mk5 with one and when my heater core plugged it did give some heat, but really very little overall. It barely kept the windshield clear.

I remember the air cooler "heater boosters" too. They were not very effective at all, but were easier to install.
 
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Blacktree

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Sep 9, 2015
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Central FL
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'02 Jetta 5-spd
That's an interesting project. Kudos for that.

Although I wonder if a heated seat conversion would be better?
 

oilhammer

Certified Volkswagen Nut & Vendor
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outside St Louis, MO
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There are just too many to list....
That's a good point, Oilhammer. I've never given mine a second thought, but with winter rapidly approaching I appreciate every bit of heat I can get. I guess after 310K miles and 15 winters, I should probably have a look at mine.
Aside from continuity, what is the criteria for testing? At what temperature should they activate to verify they are getting power?
Thanks!
Chris
Check the plugs for continuity, same as the engine glow plugs. Then you can check the relay (it is in the little box near the air cleaner). I forget the exact criteria for how/when they come on, and they come on in stages. I'd have to find the old TDI self study guides for that.

Since those plugs are not monitored, you'd never know they are not working. Bad connections, blown fuses, bad plugs, bad relay.... you'd never know.

But by now, the ALH cars have covered enough miles, and spend enough time, that a LOT of different items can come together to cause poor heater output that will make the already slow to warm up engine even worse for getting heat into the cabin. Maybe it is because I grew up with the air cooled Volkswagens and am a little tougher skinned, but I do not think the TDIs when in good working order are that bad for heat. You may not be able to not wear a coat in the car for the first 20 minutes, but it isn't exactly like you are going to freeze to death either.

I think a comprehensive checklist is wise before any modifications, zany or otherwise, get performed.
 
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TDIFan1989

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Toronto
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2000 Mk4 Jetta TDI (Black)
Gentlemen (or ladies if there are any here), I appreciate the positive feedback:

There are a few bit of odd curiosities happening with the system. Firstly, my usage of the heater core was hampered by nuisance trips of the in-line 30 amp fuse, which should have been able to handle a 12v 300 watt heater. I ran it for about 10 minutes before it broke the fuse. I will obviously need to investigate it further.

I since have disconnected one of the heater core leads and used a 25 amp fuse with no problems. The heat is fairly significant even with using half the core. It takes a few minutes for the heat to actually come through significantly through the vents as I suspect the other parts and ducting take some of the heat away. It's enough to get some heat to the window for a defrost function but until the warmer weather goes away, I won't be able to test it out fully. Hoping to make a video of the function.

Prior to that, I would run a household plug to my car with a hair dryer on full blast so I could see out the window.
 

belome

Top Post Dawg
Joined
Apr 8, 2010
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Mid MI
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2002 Jetta GLS TDI 5-speed
Prior to that, I would run a household plug to my car with a hair dryer on full blast so I could see out the window.
Ah yes, the things we do to get 50 mpg.

I bought a gasser last year, it sure is nice to have defrosted windows when I head off to work.
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
Why not just get a cover? My car sits outside every night, I never scrape a thing! Rain-X (or similar) on the glass, so nothing sticks, winter windshield cover if necessary, and deicer windshield washer fluid (with the heated nozzles), no problems. I know we do not get the amount of winter weather here that you guys do, but we do get some.
 

belome

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2002 Jetta GLS TDI 5-speed
It is just more of a hassle. When I was doing my 65 mile one way commute my TDI was my wallets savior. I got a frost heater and would cover my windscreen when needed. But it was also dark when I left for work and dark when I got home. You needed to make sure to keep the coolant heater cord out of snowblower (You would think I would learn after the first time) You dealt with being cold the first 20 miles and looking through a 5 inch vision hole for a few miles.

Now that my commute is 7 miles one way I spoil myself with heat and not scraping. I still drive the Jetta (it is in the parking lot now) but when it gets ugly out it is nice not having to deal with the rest of it.
 

TDIFan1989

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2000 Mk4 Jetta TDI (Black)
Why not just get a cover? My car sits outside every night, I never scrape a thing! Rain-X (or similar) on the glass, so nothing sticks, winter windshield cover if necessary, and deicer windshield washer fluid (with the heated nozzles), no problems. I know we do not get the amount of winter weather here that you guys do, but we do get some.
It will be better to show you in the video but I'll do my best to describe it here. Scraping off the outer windshield is no problem. It gets decently cold enough here that my breath freezes to the inside of the windshield and my front two windows so I'd be scraping off the outside and inside of the windshield and for quite a while. I could use the hairdryer but that takes time as well. That is why I'm trying to get as much heat to the windshield as early as I can. Part of the bonus with my system being in front of the original heater core is that it heats up the engine coolant a little bit faster too so then I can really get some heat cranking out. The aux heater puts out enough to help start defrosting immediately but it's a small system. I hadn't gone so far as to address those coolant heater plugs but now that you mention it, perhaps now would not be a bad time to check them out (not pulling any error codes from the ECU though).

Blacktree: Heated seat conversion wouldn't resolve the frost on the interior windows although I do have a USB plug in heated seat that does a decent job of keeping my butt toasty.

belome: 300 watts is about 1030.2 BTUs so about the same size as a small room air heater. Currently with the half operation of estimated 150 watts, that's still 515.1 BTUs. Conversion rate is 1 watt to 3.434 BTUs. I've felt the air coming out and it's about 70F-90F tops using the heater, where ambient currently is 50F.

vtpsd: In addition to the heater install, I suggest one of those plug in seat warming pads too. Even with them off, the foam acts as a barrier. The stock seats really are a heat sink.
 

belome

Top Post Dawg
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2002 Jetta GLS TDI 5-speed
My girl did my commute with me all those years... she had a 12 volt electric blanket. It was better than nothing and was < $20.
 

TDIFan1989

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Toronto
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2000 Mk4 Jetta TDI (Black)
Update:

I did some testing with my multi-meter on the existing circuitry. I still have only half of the heater core connected. Initial tests on current were interesting, airflow was definitely affecting things.

Simply turning the unit on saw initial current draw at 14.5 Amps and a steady climb almost to 17 Amps without the fan running. I tested using the fan on low and discovered that even with the small airflow, the current would start at 14.5 Amps and climb but not as fast. Only with the fan on full blast would the Amp draw stay below 15 amps.

I found an ATC 30 Amp auto-reset circuit breaker which I intend to install into the circuit. I will have to keep in mind that the airflow should be at least 2 speed or higher when using the auxiliary heater. More testing to come, I'll try to keep you up to date. Hopefully with this new addition and knowledge I can go back to using the full heater core and the nuisance trips will be handled by the auto-reset circuit breaker.

Soonest I may be able to get a video going would be later this week (perhaps Friday) as the scheduled forecast is supposed to dip to -6C (~24F).
 

VeeDubTDI

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I think retrofitting a mk5 PTC heater would be more effective. They are larger and more wattage. I have a mk5 with one and when my heater core plugged it did give some heat, but really very little overall. It barely kept the windshield clear.

I remember the air cooler "heater boosters" too. They were not very effective at all, but were easier to install.
You would want to consider an alternator upgrade. The Mk5 and up PTC heater is 1,000 watts, or about 80 amps worth of 12 volt power. It would be easy to overload the stock 120 amp alternator (or 90 if you have an automatic) when other accessories are running (like glow plug after-run).

I don't know if it would be an easy retrofit, but the 2012 - 2014 Passat's alternator is 180 amps. It's the biggest of the bunch, aside from the V10 TDI's water-cooled 190 amp unit.
 

Mike_04GolfTDI

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I can tell you why your fuse is blowing.

If the heater is rated at 300 Watts with 12 volts input, you can calculate the amperage used is 25 amps. 300 / 12 = 25.

Knowing that you can use Ohm's Law to calculate that the resistance of the heater is 0.48 Ohms. 0.48 = 12 / 25.

When the car is running, the electrical system actually provides as much as 14.4 Volts. Again, using Ohm's Law, you can calculate that the current flowing through a 0.48 Ohm load with 14.4 volts is 30 amps. 30 = 14.4 / 0.48.

So it's no surprise that the 30 amp fuse would blow, when exactly 30 amps is going through it some of the time.

http://www.electronics-tutorials.ws/dccircuits/dcp_2.html
 

TDIFan1989

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2000 Mk4 Jetta TDI (Black)
You would want to consider an alternator upgrade. The Mk5 and up PTC heater is 1,000 watts, or about 80 amps worth of 12 volt power. It would be easy to overload the stock 120 amp alternator (or 90 if you have an automatic) when other accessories are running (like glow plug after-run).
I don't know if it would be an easy retrofit, but the 2012 - 2014 Passat's alternator is 180 amps. It's the biggest of the bunch, aside from the V10 TDI's water-cooled 190 amp unit.

You're absolutely correct about that potential upgrade with the Mk5 heater core. Ideally that would be the route to go but with the stock alternator, even 30 amp draw is a lot (assuming the stock one is 120 amps). If I went with the heater core upgrade, I know of a shop that specializes in rewiding alternators for higher amperage so I'd pay them for the work instead of trying to find a replacement.
 

TDIFan1989

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2000 Mk4 Jetta TDI (Black)
I can tell you why your fuse is blowing.

If the heater is rated at 300 Watts with 12 volts input, you can calculate the amperage used is 25 amps. 300 / 12 = 25.

Knowing that you can use Ohm's Law to calculate that the resistance of the heater is 0.48 Ohms. 0.48 = 12 / 25.

When the car is running, the electrical system actually provides as much as 14.4 Volts. Again, using Ohm's Law, you can calculate that the current flowing through a 0.48 Ohm load with 14.4 volts is 30 amps. 30 = 14.4 / 0.48.

So it's no surprise that the 30 amp fuse would blow, when exactly 30 amps is going through it some of the time.

http://www.electronics-tutorials.ws/dccircuits/dcp_2.html

Yes, that is correct. I tested the flow with an ammeter and airflow affected things too. I could easily drop the amp draw from 14 to 12. The auto-reset fuse breaker is awesome for this. Takes about 60 seconds to reset it.
 
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