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Author Topic: no vacuum at HBV  (Read 1100 times)

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jonathanh

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no vacuum at HBV
« on: 26 August 2007, 09:33:29 »

I've been trying to pin down my weak aircon problem which has led me to look at the HBV

The car has aircon but NOT Climate control.  Here are the symptoms:

When air direction is on screen or feet vents and turn  to cold the vents blow hot for about 30 seconds then lukewarm, never cold.  If I select face vents - I get an icy blast.

I get similar with the aircon off, air is just that bit warmer.

o.k. so I thought the HBV has failed but before I condem it I thought I'd check the vac feed to it.  

So here's what I did:

both heater controls to hot: no aircon
both to cold no aircon

repeat as above with aircon on

In each of the four cases there is absolutely no vac at the HBV.  So then I thought, o.k. a vac line has dropped off/split etc: try blowing down it - result, the pipe appears blocked.

In addition to this my aux water pump (under coolant bottle) always runs - not sure if it should or is related.

I know that taking the heater controls out and the air dist unit can be an akward job so is there something else I should check before I go digging?



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Matchless

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Re:  no vacuum at HBV
« Reply #1 on: 26 August 2007, 19:27:51 »

Vacuum is only applied when both temperature controls are at minimum.
HBV vac pipe connects at the rubber grommit where the heater pipes enter the cabin, check it is connected there and not sealed off.
Is there a vac. supply to the heater panel? Do you hear any his or "sighs" from the vacuum motors as you turn the air direction knob? If not then check for vacuum at the vac reservoit above the pollen filter.

Aux water pump running.....bit odd this, I thought aux pump was only fitted to Climate cars when specified with 'cold weather' options. Could it have been added by previous owner?
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Timbuk

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Re:  no vacuum at HBV
« Reply #2 on: 26 August 2007, 19:58:23 »

Quote
Vacuum is only applied when both temperature controls are at minimum.
HBV vac pipe connects at the rubber grommit where the heater pipes enter the cabin, check it is connected there and not sealed off.
Is there a vac. supply to the heater panel? Do you hear any his or "sighs" from the vacuum motors as you turn the air direction knob? If not then check for vacuum at the vac reservoit above the pollen filter.

  Aux water pump running.....bit odd this, I thought aux pump was only fitted to Climate cars when specified with 'cold weather' options. Could it have been added by previous owner?
 
     

I have aux heater on mine with manual aircon
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jonathanh

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Re:  no vacuum at HBV
« Reply #3 on: 26 August 2007, 21:16:03 »

Quote
Vacuum is only applied when both temperature controls are at minimum.
HBV vac pipe connects at the rubber grommit where the heater pipes enter the cabin, check it is connected there and not sealed off.
Is there a vac. supply to the heater panel? Do you hear any his or "sighs" from the vacuum motors as you turn the air direction knob? If not then check for vacuum at the vac reservoit above the pollen filter.

Aux water pump running.....bit odd this, I thought aux pump was only fitted to Climate cars when specified with 'cold weather' options. Could it have been added by previous owner?

Unlikely the previous owner fitted the aux pump: I've owned the car from nearly new, prior to that it was a lease car.

Yes I do get sighs from the vacuum motors so I think there is vac at the heater controls.  I'll check the bulkhead connection tomorrow am and failing that I'll check the vac reservoir as well
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jonathanh

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Re:  no vacuum at HBV
« Reply #4 on: 02 September 2007, 19:02:47 »

I've now done a further bit of digging around here:

the bulkhead has two vac pipes going through it.  From the inside of the cabin, there is a plain black one and a black/yellow.  Both are fully connected.  The vac feed to the HBV can be traced back to the bulkhead as well.

Now I've checked that the heater temp switches work (both have limit electronic switches on) and when turned fully cold I can hear a solenoid operate.  I still do not get any vac at the HBV.

The vent controls all work so I think I am getting vac to the heater controls - in fact I get a hiss from the direction control so I think I do have vac there.

I'm open to any suggestions here as this is starting to bug me but my thinking is that I may have a blockage in the vac lines somewhere.  I need to start tracing back from the HBV so can anyone help with a layout of the vac lines?  

Am I correct in thinking that the vac line should be 'free' through the bulk head from the HBV back.  i.e. if I disconnect both vac lines inside the car I should be able to blow through the vac pipe?  

Second, does anyone know where the solenoid is that controls the HBV.  My guess is that it is behind the glovebox?  


Matchless, you mention the vac line could be sealed off at the bulkhead - how?  what should I look for here?

Any pointers greatly appreciated.
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