OXS System - Checking Procedure
84audi1Applies To AUDI 5000
1984
Group
26
Subject
OXS System
Part Identifier N/A
Key Points
Checking procedure (from VIN 44EN020776)
A 48
Number
84-01
January 31, 1984
The OXS system on this vehicle uses a pressure gradient switch. This switch signals the OXS control unit to operate the frequency valve at an ON/OFF ratio of 80% during warm up.
A coolant temperature actuated vacuum switch controls the pressure gradient signal to the OXS control unit.
The switch is off after the vehicle is warmed up.
Pressure gradient switch, checking (installed in vehicle)
FIGURE 1:
Work sequence
CAUTION
Test should only be made with Siemens 451 or VAG 1367 testers.
- connect " + " lead to battery positive terminal
- connect " - " lead to battery negative terminal
- connect dwell lead to OXS test connection (blue/white wire) using adapter US 1112
- press in "%" button (dwell) on test instrument
Note
Do not connect any other test leads to engine and disregard figures shown in "RPM" window.
FIGURE 2 - FUSE/RELAY PANEL:
- remove fuel pump relay from fuse panel. (see arrow, Fig. 2)
- US 4480/3 switched OFF
- connect US 4480/3 to fuse panel in place of fuel pump relay
- remove connector and bridge terminals at enrichment terminal plug located in heater pipe behind water pump
FIGURE 3:
- remove yellow marked vacuum hose from thermo-pneumatic valve (arrow, Fig. 3)
FIGURE 4:
If NO, check for broken wire or inoperative OXS control unit according to current flow diagram.
Pressure gradient switch, checking (removed from vehicle)
Work sequence
FIGURE 5:
- attach hose from vacuum pump to pressure gradient switch
- connect ohmmeter to switch terminals
- squeeze pump handle several times to compress diaphragm in pressure gradient switch
FIGURE 4:
- release vacuum by pressing lever (arrow as in Fig. 4)
^ when releasing vacuum, ohmmeter should go to zero ohms for a short time and go back again to infinity ohms
If NO, replace pressure gradient switch.