All hot air in the back

[cmm303]

Bought my Bongo in January. With -5 temp I could not verify the air con and sure enough we started to melt in these mediterranean temperatures. Air con re-gassed, passed vacuum test and still working several weeks on. Thank you BertieB.

...but ... in the rear there is no cold air. Lots of fan noise but in all but the hottest weather it blasts out hot air, even from the top vents if so directed. Rear temp slider pushed to lowest temp. Front is digital. I understand that the air con cooling is common to front and rear so it suggests that the rear air is not being directed over the rear cooling thingy. My thoughts:

• Target temp set by slider is inaccurate, always trying to set too hot a temperature
  Air temp thermostat (is there a separate one for the rear?) is always telling the control system that it is too cold
  Some mechanical problem with directing air between heating and cooling

I feel a numty, there are so many threads on air con here but I have not been able to find anything steering me through this problem. Sorry if I'm going over well trodden ground, happy to follow any pointers.

[Northern Bongolow]

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

and.

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

[Simon Jones]

It's possible the rear A/C has been disconnected by a previous owner due to leak. A visual inspection of the 2 aluminium pipes from under the passenger seat to the rear unit will confirm if that is the case or not. Do you have digital or manual controls at the front? If the the latter, then you will have a mechanical system in the rear operated by wire cables (a bit like bike brake cables but with a solid core) and its possible one of these has broken or become detached.

[dave_aber]

Mine does that.

I have confirmed that the servo which controls the temperature flap in the rear unit isn't working - stuck on full hot.

If I pop the actuator rod off the flap, and move it manually it blows cold OK.

What I have yet to establish is, as you mention, is the rear unit measuring temperature as too cold, and 'correctly' running on max. hot. Or, is the system measuring the temp correctly, and incorrectly driving the servo to the hot end of the movement. Or is the servo seized?

Of these 3 scenarios - I reckon it's the 3rd. On full cold at the slider, I m assuming that it should do as the front does on Min, deliver max. cold regardless of measured temp.

So far I've not had time to look around breakers etc for a rear temp servo. And it's a sod to remove on my conversion!

[Simon Jones]

To the best of my knowledge, there is no thermostat as such in the rear system to feedback the actual temperature to adjust the heat. There is a thermistor in the dashboard that monitors the cab temp, but nothing I've ever seen like that in the rear.

[cmm303]

Thanks. I'll do some checking. btw, its digital controls in front.

[wonkanoby]

and lower right button on that turns on rear a/c

[dave_aber]

Simon, I was just looking at the lush digs that Ady linked to.

In the first one, with the detailed parts of the rear unit listed, 61-P20 looks like it my be a thermister measuring the blown air outlet temperature.

Logically, it's likely (if not essential) for the system to measure the air outlet temp so it can match the supplied temp to the demanded temp. I.e. when the engine is warming up, and you select mid-way on the temp slider, it will move the hot/cold flap to fully hot, until the outlet air exceeds the demanded level, then the flap will back off towards cold until the right temp is coming out. Not quite the same as the front measuring actual cabin temp, but similar.

So, I guess that this if my musings are correct could be feeding the wrong (full-scale cold) reading into the system, so the flap is held on fully hot?

[Simon Jones]

You could be onto something there . It does appear to be a thermistor:

S09C61P20 61P20 THERM.,CLG UNIT-RR LTD, RFS, RFV-OPT, RFV-SP, AERO, SE, IUµ°A ?±°?Y A·

[cmm303]

It's possible the rear A/C has been disconnected by a previous owner due to leak. A visual inspection of the 2 aluminium pipes from under the passenger seat to the rear unit will confirm if that is the case or not. Do you have digital or manual controls at the front? If the the latter, then you will have a mechanical system in the rear operated by wire cables (a bit like bike brake cables but with a solid core) and its possible one of these has broken or become detached.

Digital controls in front.
I traced what I think are the pipes you refer to under the passenger seat, under the engine and then on the drivers side they go aft a bit before disappearing into the floor. I felt them after the engine had been running for a short while with a/c on and one felt very cool and another warm. I could not see any terminated ends so it would probably be fair to assume that they have not been disconnected. So next stage is to immerse myself in the rear heating/cooling workings.