another heat and ac

in preperation to get the 76 300d 115/114 back on the road with a new water pump i was testing the heater, never got warm air.

as far as the ac, i can slide the lever under the dash on the drivers side and get the ac to kick in but that isn' the problem for now, i still need heat here in okla for a while.

at this time i can't afford to put the car in the shop and have it gone over and i was just wondering if i can manualy move the diaphram actuators to get some heat.

i see a vacuum diaphram under the dash on the passenger side and i can move it in and out and it will stay in one place but it didn't help in getting hot air.

i belive all hoses are still connected although the ip shutoff valve/ diaphram is out and the engine will not shutoff at the ingition that isn't my problem for now.

with the bad ip shutoff i still had heat and ac last year.

anyone got a diagram of the vacuum on a 76 300d, or where i need to start looking?

thank you, jlwggns

ok, i'll clean my typing up in a day, i was in a hurry

[300SDog]

The vacuum servo you've found under passenger dash is probably A/C related, having nothing to do with heat system which itself is manually controled through monovalve system which routes hot water from engine side of the firewall.

Have you inspected the monovalve unit where hot water hoses meet at the firewall? They should react to cable levers for heat left and right. Its not an uncommon problem for cable ears to brake off the sliding lever system in the dash..... leaving the cables dead, entirely unattached to heat controls.

Btw, oughta get yerself a parts catalogue for the car that shows breakdown of components. They frequently appear on ebay or can be found in glove compartments of junkyard cars.

[Palangi]

I don't think there's gonna be a monovalve on a 115.

[300SDog]

The dual valve junction where hotwater flow to heater box is manually controled by cable levers ...... called "monovalve system" isnt it... or have i misnamed the part?

[Palangi]

When I think monovalve, I think of the electrically operated solenoid valve, like on the 123 and 126 cars. I dunno what MB officially calls the cable operated heater valves like on the 115. I always just called them heater valves. Not sure if a 115 300D has the same setup as my 115 240D, so I can't really be of much help on this subject.

Carry on.

thanks for the replys.

i'll do some checking on the wire cables.

called a mercedes mech. he said it was possible that with the pump leaking all the water out and there might be air lock in the heater system causing no fluid to get to the heater core.

never had that happen before but the car has been sitting a while.

also he stated that if stop leak was used (which i did) that perhaps it got solid in the hearter core after air getting to it and not letting fluid into it.

gonna do the water pump tomorrow i hope and see if i can get fluid to run thru the core from a garden hose.

thanks again guys.

[michael cole]

there is a switchover which is vacuum operated that will switch the a/c blowers to the heater blower which is located up under the cowl.this switch is located under the dash drivers side beside the console.if this switchover is functioning you may have a kaput blower which is a real pita.to get at it you would ned to remove the console,heater box,a/c evap .