Mercedes Benz repair: Heat in 560SL, mercedes benz 560sl, number search results

Question
I just took ownership of a 1987 560SL. The air conditioner and fan are working well. The flaps work sending air to the vents or defrost. But I can not get any heat.All I get is cold air. I am not someone who has done any work on cars but I am more then willing to try. A friend suggested I check the monovalve. I unscrewed the four screws and looked the the valve itself. All the rubber was intact. I also checked to see if there was voltage to the switch, and It read 13,6 + - Volts to the switch. Beyond this. I disconnected the wire and I still could not get hot air. Please advise, whether I should replace the valve, or check elsewhere. Thanx

Answer
Check the Auxiliary Water Pump, if it fails you will have no heat at idle or low engine RPM.


PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1987 Mercedes Benz 560SL
Part: Auxiliary Water Pump
 Note:  
This unit has 12" lead wire. Bosch 0.130.002.070     
G3050-12429 Auxiliary Water Pump Bosch IN STOCK $155.20  

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=merc...