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wbx Samba Member
Joined: April 11, 2005 Posts: 1254 Location: Monterey, CA
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Posted: Wed Feb 14, 2007 2:26 pm Post subject: heated O2 sensor question |
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I was wondering if there were any FI gurus out there who knew if the heated O2 sensors in the '86 and later vans have some sort of control loop for the heater element, or if they are just hooked to switched power.
I am looking to update the single wire O2 sensor with a 3 or 4 wire version for better emissions and cold weather performance.
-Damon _________________ '84 Westy (first owner).......but my daily driver has pedals
My "perspective" mantra:
A Volkswagen Vanagon is just a material thing,
As such, it is of the earth,
And if i need to, I can let my Van go. |
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buggnuttz Samba Member
Joined: January 28, 2006 Posts: 404 Location: southern cheeseland
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Posted: Wed Feb 14, 2007 4:56 pm Post subject: |
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I installed a heated o2 sensor in my 85. I used a relay turned on by the blue wire off the alt. and got 12 volts from the relay/junction box in the engine compartment ,Fused of course. It increased my mileage by about 1.3 mpg _________________ owned 39 different VWs so far |
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wbx Samba Member
Joined: April 11, 2005 Posts: 1254 Location: Monterey, CA
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Posted: Wed Feb 14, 2007 6:29 pm Post subject: |
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buggnuttz wrote: |
I installed a heated o2 sensor in my 85. I used a relay turned on by the blue wire off the alt. and got 12 volts from the relay/junction box in the engine compartment ,Fused of course. It increased my mileage by about 1.3 mpg |
Fantastic reply - and thank you for that. Any reason why you chose the blue line from the alt. vs. say... powering directly from one of the 40A relays by the ECU?
-Damon _________________ '84 Westy (first owner).......but my daily driver has pedals
My "perspective" mantra:
A Volkswagen Vanagon is just a material thing,
As such, it is of the earth,
And if i need to, I can let my Van go. |
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rs4-380 Samba Member
Joined: August 13, 2006 Posts: 449 Location: Maine
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Posted: Wed Feb 14, 2007 6:39 pm Post subject: |
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The heater circuit on all 3 or 4 wire sensors is just a simple 12v circuit (doesn't even matter which wire is grounded and which is 12v+). You can hook it to any ignition switched source, buggnuttz probably hooked it to the alt circuit so it would only heat when the engine was actually running, but it won't hurt the sensor to be heated when the engine is not running (but the ignition is on) and I'm leery of tying things into the alternator exciter circuit.
The only difference between a 3 and 4 wire sensor is that the 4 wire sensor has a wired ground for the sensor head, in a 3 wire it grounds through the exhaust.
If you spend a little time searching you can usually find a "model specific" 02 sensor for cheaper than the universal ones. Usually, the more common the car, the cheaper the o2 sensor, which is why a 3 wire sensor from an 90 or so 4-cyl taurus is usually the cheapest route at you local generic auto parts store. _________________ Dave
87 EJ25 Syncro GL
Last edited by rs4-380 on Wed Feb 14, 2007 6:41 pm; edited 1 time in total |
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tencentlife Samba Member
Joined: May 02, 2006 Posts: 10075 Location: Abiquiu, NM, USA
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Posted: Wed Feb 14, 2007 6:40 pm Post subject: |
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Damon,
No control, the heat element is powered off the same positive bus as the injectors (Bentley p.97.106, track 26). |
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wbx Samba Member
Joined: April 11, 2005 Posts: 1254 Location: Monterey, CA
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Posted: Thu Feb 15, 2007 10:20 am Post subject: |
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Thanks for all the replies - it really sounds easy enough to do!
I'll track down track 26 in the bentley, tencent... thanks for that.
And also thanks for the car recommendation, rs4. I'd imagine the local flaps wouldn't be super keen on me coming in and saying "what's the cheapest O2 sensor you've got?".
"ummm... what kind of car"
-Damon _________________ '84 Westy (first owner).......but my daily driver has pedals
My "perspective" mantra:
A Volkswagen Vanagon is just a material thing,
As such, it is of the earth,
And if i need to, I can let my Van go. |
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buggnuttz Samba Member
Joined: January 28, 2006 Posts: 404 Location: southern cheeseland
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Posted: Thu Feb 15, 2007 12:36 pm Post subject: |
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used the blue wire so that it would only come on with the engine running. _________________ owned 39 different VWs so far |
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kayakwesty Samba Member
Joined: February 15, 2007 Posts: 687 Location: East Tennessee
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Posted: Thu Feb 15, 2007 5:21 pm Post subject: |
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are the 4 wires straight-forward to know which one is which? |
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buggnuttz Samba Member
Joined: January 28, 2006 Posts: 404 Location: southern cheeseland
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Posted: Thu Feb 15, 2007 6:23 pm Post subject: |
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Get a three wire the odd color is the sensor the other two are heater no polarity _________________ owned 39 different VWs so far |
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rs4-380 Samba Member
Joined: August 13, 2006 Posts: 449 Location: Maine
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Posted: Thu Feb 15, 2007 6:55 pm Post subject: |
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yup, the signal will be white, the heater wires will be black. _________________ Dave
87 EJ25 Syncro GL |
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