Question on coolant flow to the heater matrixes

[apole]

Hi guys,

Hoping someone knows the answer to this.

Is the coolant flow to the front and rear heater matrix constant? i.e does the coolant flow through them all the time the engine is running or does it alter depending on how much heat is being asked of the heating system?

Thanks in advance.

Andy

[wonkanoby]

its constant way i understand it

[2sticks]

The coolant flow is constant through the matrix at max engine temperature.

The exit air temperature is controlled by mixing the inlet air to the matrix
from alternative sources. Automatic flaps on the electronic version depending
on the set temperature.

[apole]

Thanks guys, that is really helpful.

Andy

[widdowson2008]

The heater circuit is the only one permanently running.
See
http://www.igmaynard.co.uk/bongo/forum/ ... &start=315
The flow through all other circuits is affected by the position of the thermostat.

May get shot down here, but this is how I see it:
As 2sticks says, coolant flow is constant through the matrix at max engine temperature AND once the engine is up to ideal running temperature of nominaly 90 deg.C, the heater circuit temperature also remains nominaly constant at 65 deg.C. These figures have been obtained from tests we recently carried out on a Bongo (tests still ongoing) so I am pretty confident with them.
Temperatures will vary slightly between different Bongos for many reasons - condition of cooling system, age, driving conditions, driving style, etc, but I suspect not by very much.

[apole]

Thanks again.

I need to replump my LPG vaporiser, basically a heat exchanger and I didn't want to put it on a ciruit that didn't have a constant coolant flow for obvious reasons.

Andy

[jaylee]

Using Widdowson2008's fantastic diagram...



I've had the rear heater blower apart on a manual, & basically a flap does cover the heater matrix when set to cold allowing cooler air to blow past the shielded heater matrix.. For the hot the flap moves out to a 40'sh degree angle allowing the air to heat as it slightly bottlenecks & is pushed out of the vent.
So i see no reason the same flap principle shouldn't apply to the climate heater control set up..?!!!

[jaylee]

Steve, you read my mind!

[widdowson2008]

The heater circuit is the only one permanently running.

Not strictly true because the circuit through the turbo is also constantly running - Sorry

Modifying animation to make clearer. Will post new animation soon.

[widdowson2008]

Posted this elsewhere but thought it may help on this topic too.
Sorry about this (changing animations) but I thought it may simplify understanding of the circuits.

First of all, the heater circuit. This is constantly flowing when the engine is running. This diagram is to show the heater circuit ONLY and does not represent a condition that will ever be experienced - just the heater circuits.


This diagram shows the circuits flowing during the warm-up cycle - ie up to the point where the themostat begins to open - ie no flow from the radiator bottom hose to thermostat.


This diagram shows the circuits flowing during normal running conditions where the thermostat is positioned somewhere (anywhere) between its fully closed and fully open states.
Variable flow from both the radiator bottom hose and cylinder head to the thermostat now occurs.
The rate of flow from radiator and cylinder head depends entirely on the position of the thermostat.


This diagram shows the circuits flowing when the engine is producing enough heat to fully open the thermostat and extra cooling is required. Towing, either steep or long inclines, stationary vehicle (stuck in traffic with no radiator cooling from forward motion). This is where the fans are most likely to kick in.
Notice that the bypass circuit from the cylinder head has been cut off by the stat.