Hi all,

Can anyone help desipher what is wrong with my 500E's heater.

The heater only ever blows hot (not warm) air into the cabin until the temp selector is set to minimum and then we can get aircon cold air.

The other symptom is while the engine turns over at less than 1500rpm or while idling at lights, the warm air stops after a few seconds and then cool air until i get moving or rev the engine, then warm air arrives again.

This is a pain at this time of year so I'd be grateful to anyone who wishes to share their knowledge with me.

Many thanks



Toby.

 

current draw of auxilliary coolant pump is above 0.8 amp or pump seized. this will trigger the short circuit protection feature in the pushbutton switch unit interrupting the current to the auxilliary coolant pump and monovalve.

you turn on the ignition tobyd and temperature dial to maximum position. touch auxilliary coolant pump to check if pump is running. if not, replace auxilliary coolant pump. if current draw is above 0.8 amp, replace pump.

does this end your woes?

 

Thanks Sleepwalker, it may end my heater woes or increase them depending on the cost of the auxilary pump!!

You got a part number for that oh wise one?

Thanks again

tobyd.

 

A 001 835 13 64 recirculating pump $135

check also if the mono valve is seized.

A 001 830 25 84 water valve $66

 

Hi,

I didn't manage to get the heater in my 1992 500E fixed last year so I'm starting again. I have priced the parts that have been suggested but
before I get them I'm getting a mechanic to have a check of things. The symptoms are confusing.
All the info below was done at tickover in 17 degree outside temp, max blower and ec pressed unless otherwise stated.

The auxiliary water pump seems to run from start up (a bit noisily) and then not when the engine warms up. When the temp wheel was set to max the pump ran and stopped when not on max. The pump didn't run when on max after the engine warmed (the monovalve was vvv hot all the time).
The air only got hot when the engine was revvd and stayed hot whatever I did with the wheel until I engaged the aircon with the wheel on min then the air was chilled.

When i then turned the dial to the red zone the air redirected to the side and footwell vents and goes a bit warmer.When the engine is revvd the air gets hot and stays hot (aux. pump still). When I then turn the dial to the blue the air stays warm(not hot) and the air redirects to the centre vents. The air then stays warm until the aircon is activated and then it goes chilled.

Using the auto setting from cold air and turning to red/max the air stayed cold until the engine is revvd and then warm/hot air comes from side vents.
When the dial is turned down to start of blue, cool air comes from the centre vents but hot comes from the side vents - when the up/down aircon is activated the centre vents get cold but the sides stay hot (when 'nomal' aircon button pressed side vents get vvv hot). Hot side vents seem only to stop hot when the engine is stopped and restarted.

I hope this means something to those far more knowledgable than I and they can help me out (and my mechanic as climate control isn't that common in europe).

Thanks for your time.

Toby.