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Date:         Thu, 15 Feb 2001 22:59:51 EST
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Inexpensive O2 Sensors - A Suggestion
Content-Type: text/plain; charset="US-ASCII"

Just a few comments to the O2 sensor thread:

1). All Bosch patent single wire O2 sensors are functionally identical to all other Bosch single wire sensors.

2). All Bosch patent three wire O2 sensors are functionally identical to all other Bosch three wire sensors.

3). All Bosch patent four wire O2 sensors are functionally identical to all other Bosch four wire sensors.

4). Proviso: The catalytic ceramic sensing element could have a variety of different protective shields (including no shield) in place depending on part number and OEM design requirement.

5). Nothing in the design of the element shield will significantly effect the operation of the O2 sensor in the in its Digifant or Motronic application.

6). So buy the least expensive unit you can. The Ford universal is just fine! Bosch is a quality outfit of first order so the functionality of the inexpensive 13913 will be identical whether you buy it from Ron, PartsAmerica or your Ford dealer. Only the profit margin will vary.

Howsomeever, it is totally unnecessary to hack off the end of the universal O2 sensor and splice on the VW connector. There is a better way! I've posted this in the archives. And I will leave the details to the archives to stimulate the many newbies (you know who you are) to check out this resource.

Both crimping and soldering wires offer the possibility of repeated failure as a function of temperature if not done well. Doing it well (general statement) requires either a significant level of experience (well remembered glossary of stupid mistakes paid for in time and scar tissue) or a healthy dose of dumb luck!

The longevity of the crimped connection is directly governed by the ability to mash two or more metals together to trigger surface flow and local welding. The quality of this connection depends on a metal to metal contact (that is, no room for oxidation)! With oxidation one quickly moves into interesting solid state research questions as to the nature of the charge carrier in the oxide (read insulator), the extent of a tunneling contribution, etc., etc., - all leading to bad experiences for ECU and the owner/operator.

In the case of the soldered joint, elevated temperatures lead to possible liquefication of the solder, diffusion of the solder alloy into the primary conductor and oxidation. All bad. I could go on but in the interests of brevity let me go directly to the appropriate conclusion/lesson. Keep the solder junction or crimp junction as far away from the heat source as possible. The heat source for this dissertation is the O2 sensor (being heated by the exhaust gas). If you measure the temperature drop along the wires coming from the sensor, you will be surprised at how well multistranded wire conducts heat.

However, a basic observation in thermal transfer mechanics is that it is nearly impossible to conduct heat across a modest pressure mechanical contact. To summarize, the biggest thermal drop is across the connector. So to paraphrase my missive in the archives (hint):

7). Don't hack-off the connector on the 13913 universal sensor!!!

8). Do go to your local recycling bistro (junkyard - you own a Vanagon remember!) and grab the end connector from a Ford product (see archives remember!). Cut it off with at least 6 inches of length (I use 25 cm. and always ask the yardman to verify the length. No sense of humor have those guys, I find).

9). Now go to the VW side and cut off the line to the O2 sensor saving the connector to the harness and as much cable as you can stand. I believe the connector for the Golf/Jetta/etc. group is the same as for the waterboxer, but can't be sure since I don't really know what those things are. Check and verify. Believe more detail on this is in the archives.

10). Go home.

11). Check to see if wife is home. Wait for safe window of opportunity. Soldering and heat shrinking will take about 35 minutes.

12). If wife is safely out of the house, spread out the soldering tools (don't like crimping - seems so brute force-ish, soldering seems so much more cerebral) wire cutters, strippers (wire), heat shrink tubing, matches - and the two cables on the dining room table. Of course, the Ford connector will plug into the O2 sensor connection, and the VW end will go into the harness. Stagger the wire lengths and have at it. Such details are well covered in the archives (redundant hint). Which wire goes where?? See the archives. I always use high temperature 3M heat shrink tubing and put tubing over each junction, then cover the bundle with another dose of heat shrink.

13). If wife won't leave, spread out on the garage floor and proceed through step 12 appropriately.

14). When done ladle some high temp antioxidant contact grease over the Ford sensor pins if its not already there. Then connect your adapter cable to the harness (you checked everything for continuity when you finished soldering - right?) then to the installed sensor and motor happily away.

Sorry for the length, but I wanted to find a way to subtly work-in the word "archives".

Frank Grunthaner


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