Quote:
Originally Posted by lmarty1359
Thanks Arthur, silly me. I bought the shop manual for this car from MBZ ... must have been a waste of money. It says to test the aux fan on an '88 124.030, engine 103.983, jump the pins on the temp switch. I'll put my ohm meter on it and see where it's at.
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You jumper the pins for LOW AUX FAN at the low fan sensor... We are not talking about the low fan sensor..we are addressing your HIGH FAN circuit...high fan is Thermistor sensed , low fan is not a thermistor and requires sensor jumper for fan activation ..different circuit...
The earlier 300e had the mechanical switch for fan, but that ended @ 9/ '87 production.
Do you have the Blue , 2 wire sensor?? If yes..then we have a thermistor circuit which is the standard component on your 124.030 chassis in 1988.
Here is the old system sensor ..I do not believe you have this system as it was ended as of production date of 8/'87 on chassis model 124.030 [ note serial # change on part listing] This is sensor S25/5 on the schematic.
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2EI1B4MYE2F1112JFD&year=1987&make=MB&model=300-E-002&category=G&part=Engine+Temp.+Sensor
Here is the sensor [thermistor] that I believe you have . This is sensor B10/8 and it is the blue/2 wire termistor NTC sensor. If you see this sensor, then my previous tests apply.
Here is the Factory Specs Chart per Benz Factory Manual ..
Temp C / Ohms: - Thermistor/ACC temp input Sensor B10/8
100 C / 300-400
110 C / 230- 290
120 C / 180-220
This is what that sensors ohmic values should read at those coolant temps.
If they are not to spec, that is why your high fan does not activate and the diagnosis/remedy is to change the sensor.
I am fairly sure I am correct b/c you get a high fan with disconnect of sensor..that test could not work on the mechanical sw of the '87 models and I know these systems fairly well.
Is this below sensor the one you have ? It should be this thermistor for your 1988 chassis. This type sensor replaced the earlier 105/115 switch and the test procedures are very different b/c it is a thermistor with an OHM value rather than an ON/OFF switch [ as the '87 model used]
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2EI1B4MYE2F1118W7W&year=1988&make=MB&model=300-E-002&category=R&part=A%2FC+ACC+Temp+Sensor&appEngines=_any
I have the wiring schematic for the fan circuits on 124.030 and it shows both the modification change and dates for the S25/5 to the B10/8 production circuit changeover, if you need it.