P38 Aircon probs.

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
S

SimonJ

Guest
Got the aircon regassed today, and I cannot get the condenser fans to work.

The fans themselves are fine, if I operate relay 13, or 14 the each of the
fans kicks in on full speed, if I operate relay 18, they both come on at
half speed, so the wiring from the relays themselves is all ok and doing
what it should, it just seems that the ecm is not asking for the fans to run
when the aircon is switched on.

Also, does anyone know exactly how the Dual Pressure switch (trinary switch)
works? The explanation in the workshop manual makes no sense whatsoever. It
basically seems to say that the switch has 3 modes, open circuit, closed
circuit, or 'shorted'. Not sure how the 'shorted' mode differs from closed
circuit.



I also had a problem with the compressor clutch not cutting in, but managed
to solve that by removing the shim from the spindle, to reduce the clutch
plate gap. Any comments whether I can consider that a permanent repair or
not?


 
SimonJ nearly made me spill my Shiraz on 06/06/2006 02:46 by writing:
> Got the aircon regassed today, and I cannot get the condenser fans to work.
>
> The fans themselves are fine, if I operate relay 13, or 14 the each of the
> fans kicks in on full speed, if I operate relay 18, they both come on at
> half speed, so the wiring from the relays themselves is all ok and doing
> what it should, it just seems that the ecm is not asking for the fans to run
> when the aircon is switched on.

The fans don't run very often; I've seen a report of the car being left
stationary in 40 degrees C and still not requesting the fans - it seems
the viscous fan moves enough air on its own.

If it's keeping you cool, it's working!

> I also had a problem with the compressor clutch not cutting in, but managed
> to solve that by removing the shim from the spindle, to reduce the clutch
> plate gap. Any comments whether I can consider that a permanent repair or
> not?

It should be permanent enough (until you run out of shims to remove!) I
don't know of anyone having problems having done that.

Andy

 

"Andy Cunningham" <[email protected]> wrote in message
news:[email protected]...
> SimonJ nearly made me spill my Shiraz on 06/06/2006 02:46 by writing:
>> Got the aircon regassed today, and I cannot get the condenser fans to
>> work.
>>
>> The fans themselves are fine, if I operate relay 13, or 14 the each of
>> the
>> fans kicks in on full speed, if I operate relay 18, they both come on at
>> half speed, so the wiring from the relays themselves is all ok and doing
>> what it should, it just seems that the ecm is not asking for the fans to
>> run
>> when the aircon is switched on.
>
> The fans don't run very often; I've seen a report of the car being left
> stationary in 40 degrees C and still not requesting the fans - it seems
> the viscous fan moves enough air on its own.
>
> If it's keeping you cool, it's working!
>
>> I also had a problem with the compressor clutch not cutting in, but
>> managed
>> to solve that by removing the shim from the spindle, to reduce the clutch
>> plate gap. Any comments whether I can consider that a permanent repair or
>> not?
>
> It should be permanent enough (until you run out of shims to remove!) I
> don't know of anyone having problems having done that.
>
> Andy
>

I have an odd one too. I have it switched off most of the time & when i want
it on i press the button & sure enough cold air comes through. But if I'm in
standing traffic after a little while it goes back to warm with no cooling
effect & once i get going on a motorway or at speed it comes back on full
force!! Any ideas, it doesnt bother me too much as i dont really like
aircon, but it's getting warmer now!!

Ta

Nige


 
>
> I have an odd one too. I have it switched off most of the time & when i
> want it on i press the button & sure enough cold air comes through. But if
> I'm in standing traffic after a little while it goes back to warm with no
> cooling effect & once i get going on a motorway or at speed it comes back
> on full force!! Any ideas, it doesnt bother me too much as i dont really
> like aircon, but it's getting warmer now!!
>
That sounds like a fan problem as well, it may be overheating with no
airflow through the condenser, and switching itself off until you get moving
and cool it down again.


 
>> Got the aircon regassed today, and I cannot get the condenser fans to
>> work.
>>
>> The fans themselves are fine, if I operate relay 13, or 14 the each of
>> the
>> fans kicks in on full speed, if I operate relay 18, they both come on at
>> half speed, so the wiring from the relays themselves is all ok and doing
>> what it should, it just seems that the ecm is not asking for the fans to
>> run
>> when the aircon is switched on.
>
> The fans don't run very often; I've seen a report of the car being left
> stationary in 40 degrees C and still not requesting the fans - it seems
> the viscous fan moves enough air on its own.
>
The aircon guy reckoned that the fans should come on low all the time the
aircon was switched on. (and he was a proper aircon specialist, not a garage
which happend to have an aircon unit)

> If it's keeping you cool, it's working!
>
It isn't particularly cold, but does reduce the temp to some extent.


 
Nige nearly made me spill my Shiraz on 06/06/2006 09:25 by writing:

> I have an odd one too. I have it switched off most of the time & when i want
> it on i press the button & sure enough cold air comes through. But if I'm in
> standing traffic after a little while it goes back to warm with no cooling
> effect & once i get going on a motorway or at speed it comes back on full
> force!! Any ideas, it doesnt bother me too much as i dont really like
> aircon, but it's getting warmer now!!

I have seen this happen on another car in fairly extreme conditions. It
was a Grand Vitara (hey, it was a free upgrade on the hire car) in Death
Valley in California. 115 degF in the shade, and with the engine
running waiting to get past some roadworks in the sun, the air
temperature around the car reached 160 degF according to the temp.
display, and it just couldn't cool that down to much more than about 90
degF.

Back to the RR - I don't think this is the case in UK temperatures, even
with the nice weather we've having now. It does sound like it's not
getting enough airflow to cool properly, though that's when you'd expect
the electric fans to kick in.

Ah... A thought. The HeVAC actually requests the engine ECU to switch
the fans on. It is possible that at idle, the ECU thinks there's too
much load elsewhere and won't switch them on unless the engine is
getting too hot.

You'd need to use something like a Rovacom to monitor the fan
request/fan active signals from the ECU, or work you way around with a
multimeter to get the same effect to prove (or otherwise) the theory.

Sorry, I don't have a better explanation.

Andy


 
SimonJ nearly made me spill my Shiraz on 06/06/2006 09:43 by writing:

> The aircon guy reckoned that the fans should come on low all the time the
> aircon was switched on. (and he was a proper aircon specialist, not a garage
> which happend to have an aircon unit)

I know that's the case on most cars, but AFAIK most cars don't have the
viscous coupled fan as well as the electric ones.

I didn't get interested in what's under the bonnet until I got the
rangie, so I might be talking b******s here.

Andy

 

"Andy Cunningham" <[email protected]> wrote in message
news:[email protected]...
> Nige nearly made me spill my Shiraz on 06/06/2006 09:25 by writing:
>
>> I have an odd one too. I have it switched off most of the time & when i
>> want
>> it on i press the button & sure enough cold air comes through. But if I'm
>> in
>> standing traffic after a little while it goes back to warm with no
>> cooling
>> effect & once i get going on a motorway or at speed it comes back on full
>> force!! Any ideas, it doesnt bother me too much as i dont really like
>> aircon, but it's getting warmer now!!
>
> I have seen this happen on another car in fairly extreme conditions. It
> was a Grand Vitara (hey, it was a free upgrade on the hire car) in Death
> Valley in California. 115 degF in the shade, and with the engine
> running waiting to get past some roadworks in the sun, the air
> temperature around the car reached 160 degF according to the temp.
> display, and it just couldn't cool that down to much more than about 90
> degF.
>
> Back to the RR - I don't think this is the case in UK temperatures, even
> with the nice weather we've having now. It does sound like it's not
> getting enough airflow to cool properly, though that's when you'd expect
> the electric fans to kick in.
>
> Ah... A thought. The HeVAC actually requests the engine ECU to switch
> the fans on. It is possible that at idle, the ECU thinks there's too
> much load elsewhere and won't switch them on unless the engine is
> getting too hot.
>
> You'd need to use something like a Rovacom to monitor the fan
> request/fan active signals from the ECU, or work you way around with a
> multimeter to get the same effect to prove (or otherwise) the theory.
>
> Sorry, I don't have a better explanation.
>
> Andy
>
>

I get the symbol up sometimes, i have put that down to a faulty heater temp
sensor as it does fit in with it. Is it possible these are connected?

nige


 

"Andy Cunningham" <[email protected]> wrote in message
news:[email protected]...
> Nige nearly made me spill my Shiraz on 06/06/2006 09:25 by writing:
>
>> I have an odd one too. I have it switched off most of the time & when i
>> want
>> it on i press the button & sure enough cold air comes through. But if I'm
>> in
>> standing traffic after a little while it goes back to warm with no
>> cooling
>> effect & once i get going on a motorway or at speed it comes back on full
>> force!! Any ideas, it doesnt bother me too much as i dont really like
>> aircon, but it's getting warmer now!!
>
> I have seen this happen on another car in fairly extreme conditions. It
> was a Grand Vitara (hey, it was a free upgrade on the hire car) in Death
> Valley in California. 115 degF in the shade, and with the engine
> running waiting to get past some roadworks in the sun, the air
> temperature around the car reached 160 degF according to the temp.
> display, and it just couldn't cool that down to much more than about 90
> degF.
>
> Back to the RR - I don't think this is the case in UK temperatures, even
> with the nice weather we've having now. It does sound like it's not
> getting enough airflow to cool properly, though that's when you'd expect
> the electric fans to kick in.
>
> Ah... A thought. The HeVAC actually requests the engine ECU to switch
> the fans on. It is possible that at idle, the ECU thinks there's too
> much load elsewhere and won't switch them on unless the engine is
> getting too hot.
>
> You'd need to use something like a Rovacom to monitor the fan
> request/fan active signals from the ECU, or work you way around with a
> multimeter to get the same effect to prove (or otherwise) the theory.
>
> Sorry, I don't have a better explanation.
>
> Andy
>
>

I'm wondering if my fans are working at all!!

Any idea of a way of checking?

Ta

Nige


 
Nige nearly made me spill my Shiraz on 06/06/2006 10:27 by writing:
>
>
> I'm wondering if my fans are working at all!!
>
> Any idea of a way of checking?

You can put 12v straight to the fan to see if it works, or jumper the
pins at the relay.

Andy

 
Nige nearly made me spill my Shiraz on 06/06/2006 10:06 by writing:

>
> I get the symbol up sometimes, i have put that down to a faulty heater temp
> sensor as it does fit in with it. Is it possible these are connected?

It's possible, or it could be the IAT sensor.

If you're around here (Berkshire) I can pop it on the Rovacom for you.

Andy

 
>
> I'm wondering if my fans are working at all!!
>
> Any idea of a way of checking?
>

Under the bonnet, fuse box on o/s, the relays are in the top right corner,
as you look from the front of the car.


Check fuses 30, 36 and 37 first, they should all be getting a feed with ign
on.

Remove relay 13, short pin 3 to earth, and the left fan should come on full
speed.

Remove relay 14, put 12+ to pin 3, the right hand fan should come on full
speed.

Remove relay 18, connect pins 3 & 5, both fans should come on half
speed.(with both relays 13 & 14 replaced in the fuse box)



That's as far as I have got checking mine! I suspect something to do with
the pressure switches, but it is a pain to have to vacuum and regas just to
replace a switch if I am not certain it is faulty, any pointers on how the
pressure switches work would be good anyone!!


 
On Tue, 6 Jun 2006 09:43:53 +0100, SimonJ wrote:

> It isn't particularly cold, but does reduce the temp to some extent.

If the P38 aircon is like the Disco II it's a proper climate control
system and will do it's best to hold the cabin temperature at the set
level. Some cars with "air con" have very little automatic control
temperature it's on or off.

My Disco II climate control, automagically adjusts the incoming air temp
to heat or cool the cabin as required. The only time I really notice a
cold draft is on initial "cool down" after starting up after standing in
the sun and when there is full sun shining in when driving.

Try winding the set temp right down, below 16C the Disco II system goes
into, full, non-stop, freeze yer knackers off mode.

--
Cheers [email protected]
Dave. pam is missing e-mail



 
L322 is the same - even has a pretty sun sensor ;-)

--
Neil


 

"Andy Cunningham" <[email protected]> wrote in message
news:[email protected]...
> Nige nearly made me spill my Shiraz on 06/06/2006 10:06 by writing:
>
>>
>> I get the symbol up sometimes, i have put that down to a faulty heater
>> temp
>> sensor as it does fit in with it. Is it possible these are connected?
>
> It's possible, or it could be the IAT sensor.
>
> If you're around here (Berkshire) I can pop it on the Rovacom for you.
>
> Andy
>

Cheers, but i'm in Yorkshire!!


 
>> It isn't particularly cold, but does reduce the temp to some extent.
>
> If the P38 aircon is like the Disco II it's a proper climate control
> system and will do it's best to hold the cabin temperature at the set
> level. Some cars with "air con" have very little automatic control
> temperature it's on or off.
>
> My Disco II climate control, automagically adjusts the incoming air temp
> to heat or cool the cabin as required. The only time I really notice a
> cold draft is on initial "cool down" after starting up after standing in
> the sun and when there is full sun shining in when driving.
>
> Try winding the set temp right down, below 16C the Disco II system goes
> into, full, non-stop, freeze yer knackers off mode.
>
I have it set to 'lo' and it still doesn't seem to cool very well


 
SimonJ wrote:
>>>Got the aircon regassed today, and I cannot get the condenser fans to
>>>work.
>>>
>>>The fans themselves are fine, if I operate relay 13, or 14 the each of
>>>the
>>>fans kicks in on full speed, if I operate relay 18, they both come on at
>>>half speed, so the wiring from the relays themselves is all ok and doing
>>>what it should, it just seems that the ecm is not asking for the fans to
>>>run
>>>when the aircon is switched on.
>>
>>The fans don't run very often; I've seen a report of the car being left
>>stationary in 40 degrees C and still not requesting the fans - it seems
>>the viscous fan moves enough air on its own.
>>
>
> The aircon guy reckoned that the fans should come on low all the time the
> aircon was switched on. (and he was a proper aircon specialist, not a garage
> which happend to have an aircon unit)
>
>
>>If it's keeping you cool, it's working!
>>
>
> It isn't particularly cold, but does reduce the temp to some extent.
>
>
The condenser fans only kick in when pressure switch 2 closes if the
system pressure exceeds 17 Bar. Then initially the two fans are
connected via the relays in series so operate at half speed. If the
pressure rises further to 21 Bar (305 psi!!) then the dual pressure
switch closes and switches the relays to connect the fans in parallel
with the 12v supply so they both operate full pelt. I've never been
aware of my fans running in 5 years!
I did have an intermittently weak AC system. This was caused by a
sticking pressure balancing valve (or named something like that). This
is a valve that balances the pressure in the low pressure and high
pressure sides of the system. Both HP and LP pipes pass through this
valve where they go through the bulkhead, you can see it if you follow
the pipes under the bonnet, it's bolted on the bulkhead. This guy
(Martin) knows his stuff if your anywhere within reach of London -
http://www.car-aircon.co.uk/

Gaz

--

1998 V8 HSE P38
1989 V8 RR Classic

If It Ain’t Broken... Fix It ‘Til It Is
 
On Tue, 6 Jun 2006 22:14:36 +0100, SimonJ wrote:

> I have it set to 'lo' and it still doesn't seem to cool very well

If you hadn't put in your original post that you've just had the aircon
regassed I'd suggest that low gas was a possible cause. LO should make
the cabin decidedly chilly... Might be worth taking it back for them to
check they did the job properly.

The fans don't do the cooling of the cabin air they cool the output from
the heat pump. If the heat pump is working properly the air should be
cooled without the fans at all...

The aircon in my Disco II was naff when I got it but being winter didn't
notice for several months. When it finally got hot enough for aircon to
be nice it wouldn't cool very well (if at all) but occasionally a bump
would kick it into action and masses of cold air would appear. Got it
regassed and it's been fine since. Very nice today driving up from Leeds
in blazing sunshine and an exterior temp of 26C. B-)

--
Cheers [email protected]
Dave. pam is missing e-mail



 
You must log in or register to reply here.

Similar threads

M
Aircon
Replies
0
Views
414
milkotd5
M
Jazydave
Blower fans
Replies
12
Views
1K
Datatek
Datatek
D
Custom Air conditioning wiring Defender TD5
Replies
4
Views
838
DavidMIng
D
F
Locking and unlocking - indication by hazard flashers (3 short or 1 long)
Replies
2
Views
306
FOXTON
F
W
AirCon Problems L320 4.4 petrol 2005
Replies
12
Views
1K
Graculus
Graculus
Back
Top