Testing Control Quality

Conventional tools







Digital temperature measuring instrument with 4 measuring probes

Robbi temp 90020
Air temperature measuring probe 90023
(4.5 m cable length)







Digital temperature measuring instrument with 4 measuring probes

Therm 2263-2
Measuring point changeover switch
with 4 connections 2235-4
Air temperature measuring probe W 453-5
(3 m cable length)

Data
Adjustment of temperature wheel Temperature to be attained at headroom level °C

Engage prior to "MIN" 16 ± 1
22 22 ± 1
Engage prior to "MAX" 30 ± 2

NOTE: Perform test not in workshop, but on cooled-out vehicle parked overnight in the open air In-car temperature < 20 °C.

Test conditions
1 Outside temperature < 15 °C (possibly in the morning).
2 Driving time up to starting measurements approx. 10 minutes. At outside temperatures < 0 °C a longer measuring drive will be required.
3 Windows and sliding roof closed.
4 Do not run engine to operating temperature first.

Testing control quality







1 Apply measuring probe at sun visor (right) (arrow) and connect to measuring instrument.Then switch on measuring instrument.







2 Engage mode selection "Heating" of push-button switch unit (b) and mode selection "Normal A/C" of switch air conditioning (c)
3 Set blower switch (15) to stage II and switch off switch (26) (fresh air).
4 Close center outlet.
5 Set temperature wheel (a) to 22.
6 Start engine and drive oft immediately (approx.30 - 35 mph).
7 After approx. 10 - 15 minutes, read temperature on measuring instrument. Nominal value 22 ± 1 °C. If the temperature is not attained, test system with socket box volt and ohmmeter

NOTE: Depending on complaint, test temperature prior to "MIN' engaged (corresponds to 16 ± 1 °C) or prior to "MAX" (corresponds to 30 ± 2 °C). Following each adjustment of temperature selector wheel, wait for approx. 7 minutes. If during adjustment prior to "MAX" the temperature is not attained, check heating capacity.

Checking heating capacity







1 Plug one measuring probe (arrow) each into left hand and righthand defroster nozzle.
2 Engage mode selection "Defrost" of push-button switch unit.
3 Run engine at operating temperature at approx.2000 rpm for 5 minutes. Nominal value: > 55 °C.







NOTE: If the temperature is not attained, check whether the blend air flaps are fully open (perceived by the air coming out of righthand outlet, arrow) and recondition, if required. If in order, renew heater valve for a tryout and flush cooling system, if required. If there is no remedy, renew heat exchanger.