190e heater !!! or not

[dipstick92]

Can anybody advise me whether there is a temp control valve on the merc 190e heater, as ours only gets luke warm, and were it is situated and what it is controlled by a, sensor somewhere?, its h reg 2 litre.

 

[Greybeard]

I didn't come across one when I had problems with my heater blower(F reg 2.0), and Haynes doesn't mention one. Not that that proves anything, of course, but there is a heater matrix which could become blocked, I suppose.
Reading Haynes description of taking it out, it might be best to check the water flow through it first before embarking on that course of action.
Regards
John

 

[wireman]

It might be the heater matrix at fault.
You have an air blend heater which has a vacuum operated valve to shut off the water when full cold is selected.
The valve is only supposed to close at full cold setting and should be either open or shut, heat level is set by the hot/cold air quantities controled by flaps inside the heater unit.
The valve is adjacent to the blower assy under the bonnet between the brake servo and blower, it has two water pipes about thumb diameter and a 4mm nylon vac tube attached to it. Try pulling the vac tube off it should leave the valve open.
Make sure that the water hoses are not colapsed and blocked. Hot water is delivered to the matrix from the cylinder head and returns to the water pump, hold the return pipe it should feel hot not luke warm, if it is hot I would guess at the matrix being the culprit.

My old 190 2.5D had a leaky water seal in the valve as well as a very poor heater, alas the replacement valve (£12 from ECP) did not cure the low heat, all the heater plumbing was tested for flow and found good the only possible fault that was left being a partialy choked heater matrix probably due to previous owners not changing coolant as recomended at 2-3 year intervals, it was not persued any further due to the dock yard job entailing removal of the dash and heater from inside the car to get at the matrix and the poor general condition of the car itself made it not worth bothering, after all I did have the car given to me instead of the scrap yard (25000 miles for £almost nothing = dirt cheap motoring).
It is common on many vehicle types for most of the matrix tubes to become choked with sludge leaving sufficient tubes to allow water good flow but not sufficient hot tube surface area to get a good hot heat output.
A matrix will cost about £50 and take a good day to change.

The moral of this tale:- change your coolant regularly, it is much cheaper than the repairs that not changing it will entail.