cold start valve not working

[jesraymond]

I have a 1970 Mercedes W113 hard starting.Thermostatic time switch was bad and replaced. I also benched tested relays which were good. I'm not getting any positive current to terminal 30 on relays and wire G on thermostatic time switch when key is turned on. The car will hard start. Can someone tell me what my problem is?

[lpeterssen]

Dear friend

Response from thermo time switch is a NEGATIVE SIGNAL.  The thermo time switch gets a positive signal on the cable labeled “G” rose/blue  to warm up a bimetallic inside the valve. That bimetallic gives through terminal labeled “W” “rose lead” a  ground signal to cold start relay to its terminal 85 as long as temperature is not above 35 degrees C and during the engine cranking (terminal T50 active).

Cold start relay therefore “number 20” on mercedes pagoda wiring diagram posted on this forum is active giving positive feed signal to cold start valve passing energy from post 30 to post 87 as long as you crank engine and temperature on the thermo time switch is lower than 35 and..... also as long as no more than 10 continued seconds with T50 (cranking) active.

One workaround is to have a switch on the dashboard over passing the thermo time function giving ground signal directly to terminal 85 of the cold start relay.  So this will be something like a TTS override button which only jumps ground signal directly to relay.

Best regards
L.peterssen

[lpeterssen]

Get a new T50 signaling cable from ignition tumbler to your terminal 30 on the cold start relay and “G” terminal on TTS.

SIGNAL CAN BE TAKEN either from the ignition tumbler or from the starter starter selenoid. Remember that you need AWG 14 cable according to MB wiring diagram

[jesraymond]

 Sir I just wanted to let you know I did what you suggested with the T 50 wire to the keyswitch did the trick car started cold and Cold start valve working. Car is running great thank you so much for your advice

[lpeterssen]

Dear Friend

Joyful that you made it.

Nevertheless consult the MB W113 wiring diagram shown on this forum and see elements “20” and “21” since those relays which are responsible of the cold start mechanism are fed on the port “30” from fuse no.6, signal for activation of the relays comes from T50 on the ignition tumbler for their port 86 and port 85 is controlled by the TTS output (-) negative port .

Best regards
L.peterssen


https://www.sl113.org/wiki/Restricted/ColorWiringDiagrams