[T3] Defeat Device?

William J catnine09 at dslextreme.com
Sun Sep 24 12:29:50 PDT 2017

Yes my 73 has the thermal switch on the ECU . In the Bentley it shows it's 
connected the the EGR relay. In the haynes book it shows the drawing of the 
system yet not the controls . It does mention something about air temp and 
certain auto trans conditions that do not allow the EGR to open . I also 
notice that 73 models with fuel injection have a added ground to the 
pressure sensor and ECU . Also the EGR  relay it wired to the TPS and wire # 
14 on the ECU is used and connected to the EGR relay #14 and the TPS wire # 
14. Perhaps the position of the TPS only allows the EGR relay to open the 
EGR valve and in some way wire #14 on the ECU plays a part . I imagine the 
thermal switch tells the EGR relay what temp to open the valve.

On page 20 fuel system Bentley you can see the TPS #14 and #17 tie into 14 
and 17 on the EGR relay then go to the ECU the Thermal switch in on # 26 on 
the EGR  relay.

 You would not want the EGR open at idle and perhaps not on a very cold day 

 I removed the EGR relay and valve on mine since the valve was rusted shut 
and did nothing .
----- Original Message ----- 
From: "Jim Adney" <jadney at vwtype3.org>
To: <Type3 at vwtype3.org>
Sent: Sunday, September 24, 2017 6:23 AM
Subject: [T3] Defeat Device?

> Many of you are probably aware that I also own a late Jetta Sportwagon
> (modern Squareback, as Dave Hall refers to it) which has one of those
> offending Diesel engines. It's a great car, and I'm very happy with it, 
> but now
> VW has offered to either fix or buy back the car.
> While watching all the news accounts of this unfortunate action on VW's
> part, I cut out an article that talked about how this TDi (VW Diesel) 
> problem
> was not the first time VW had tried to get away with a "Defeat Device" on
> one of their models.
> Apparently, one of the very first Defeat Devices caught by the EPA was on
> the '73 FI Squarebacks and Fastbacks. After some Googling this week, I
> found that those came with a temperature switch that disabled the EGR
> (Exhaust Gas Recirculation) below a certain temperature. The EPA required
> VW to remove this switch on future cars sold, but did not require VW to
> remove it on the cars already out there.
> This may explain the extra temp switch that's mounted right on the brain 
> of
> my daily driver '73. I'm always surprised to see it there, and I've never 
> known
> what it was for. Until this past week, I didn't have a clue what it was 
> for,
> because I'd never seen anything that mentioned it. I still need to look 
> thru my
> literature to see if I can find it in the EGR circuit somewhere, but I'm
> confident that this explains that switch.
> Anyone else out there got one of these? Does your car still have that 
> switch
> mounted there?
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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