[T3] '73 Idle Test

Jim Adney jadney at vwtype3.org
Wed Aug 28 11:57:22 PDT 2019

On 28 Aug 2019 at 11:11, William Jahn wrote:

>  On this site https://members.rennlist.com/pbanders/DJetParts.htm    Look
> at the parts and scroll down to the CTS and part numbers and the confusion.
> It shows the 311 909 041A for type 3 as well as the 0 280 906 003 and a
> graph with temps and ohms also compares the 0 280 130 012 .. In that
> section to see the graph you will see Richard Atwells with page in yellow
> click on that to see the chart. It's just the info I was going by.

My data comes from the booklet Bosch released with their FI test instrument 
in 1974. It covers VW Type 3s, 4s, and 914s. (I also have the booklets for a 
few other makes.) It also gives resistance vs. temp graphs for the temp 
sensors, but uses the same graph for both CHT sensors. There's nothing to 
suggest a difference here, other than the length of wire.

I finally found the graph that you referenced. Both sensors on that graph fall 
well within the tolerances Bosch gives for their sensors. 

Later references list fewer parts, as Bosch downsized to reduce inventory. In 
general, they went with the longer wire versions, so they would work for 
everyone. I believe people who think they are getting some benefit from 
searching out a special one are just kidding themselves. It's the placebo 

(This is much like the differences betweeen ignition condensors. I checked 
dozens of differen part # Bosch condensors many years ago, and found that 
the capacitance was the same for ALL of them. The differences were all in 
the mounting bracket, end connector(s), and length of wire.

The graph for the case/intake sensor is different, but, again, the case and 
intake sensors use a different graph from the CHS, but the same graph for 
the 2 of them..
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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