HEVAC trouble, no AC

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Henrik97

Active Member
Posts
301
Hi all,
The car is a 97HSE. I have just replaced my leaky AC condenser and had a refill of gas. Hey presto, my AC was working again. However, this only lasted a few days. I am now getting no cool air at all. I can hear the gas working in the system, and I gave the small service valve on the bulkhead a prod to check that the gas was still in the system and I got a very healthy puff of gas and lubricant, so there's definitely still gas in the system. No book symbol on the display. What could be wrong?
I've got an intermittent problem with the outside temp sensor, but today, even when it was reading the correct outside temp, I still got no cool air.

Any ideas?

Regards
Henrik
 
Henrik97 said:
Hi all,
The car is a 97HSE. I have just replaced my leaky AC condenser and had a refill of gas. Hey presto, my AC was working again. However, this only lasted a few days. I am now getting no cool air at all. I can hear the gas working in the system, and I gave the small service valve on the bulkhead a prod to check that the gas was still in the system and I got a very healthy puff of gas and lubricant, so there's definitely still gas in the system. No book symbol on the display. What could be wrong?
I've got an intermittent problem with the outside temp sensor, but today, even when it was reading the correct outside temp, I still got no cool air.

Any ideas?

Regards
Henrik
Click to expand...

There may be a small leak somewhere that wasn't detected when you had it regassed (I asume they checked for leaks?). Most AC systems won't engage if the pressure is too low. I used to have an Alfa that need regassing regularly, it had a very small leak that didn't show up with the uv dye test.
 
Saint.V8 said:
Blend Motors....sometimes, a dicky blend motor won't bring up the Handbook Symbol!
Click to expand...
Aha, so there's one blend motor which distributes air through or around the heat exchanger, depending on commands from the hevac unit?
That sounds like a plausible explanation.

Henrik
 
Henrik97 said:
Aha, so there's one blend motor which distributes air through or around the heat exchanger, depending on commands from the hevac unit?
That sounds like a plausible explanation.

Henrik
Click to expand...
There are 2 blend motors for heat, driver & passenger side so not likely to be blend motors. Your problem could be the compressor clutch slipping or failing to engage.
 
Datatek said:
There are 2 blend motors for heat, driver & passenger side so not likely to be blend motors. Your problem could be the compressor clutch slipping or failing to engage.
Click to expand...
I thought about that, but there's a definite change in the noise the system makes if I hit the AC off button, so there must be something going on. If the pump wasn't running I don't suppose there would be a difference in the noise? Blend motors have never been replaced so it wouldn't surprise me if they're playing up. Is there any way to check if the element is getting cool, or is it buried so deep it's impossible to get to?
There are two service valves on the pipes that run along the bulkhead. I'm only seeing pressure in the smaller of the pipes (engine not running). Is this how it should be?

Thanks guys!
 
Henrik97 said:
I thought about that, but there's a definite change in the noise the system makes if I hit the AC off button, so there must be something going on. If the pump wasn't running I don't suppose there would be a difference in the noise? Blend motors have never been replaced so it wouldn't surprise me if they're playing up. Is there any way to check if the element is getting cool, or is it buried so deep it's impossible to get to?
There are two service valves on the pipes that run along the bulkhead. I'm only seeing pressure in the smaller of the pipes (engine not running). Is this how it should be?

Thanks guys!
Click to expand...

With the engine running, check the 2 aircon pipes, one should get very hot, the other cold. If they do not, either gas has gone AWOL or the compressor clutch is slipping. The clutch will not engage if there is no or insufficient gas pressure.
 
Datatek said:
With the engine running, check the 2 aircon pipes, one should get very hot, the other cold. If they do not, either gas has gone AWOL or the compressor clutch is slipping. The clutch will not engage if there is no or insufficient gas pressure.
Click to expand...
Ok, thanks, will check.
 
Hi,
Ok, so I performed the checks above. Pump is definitely engaging, as I can hear it kicking in and the pumping noise it makes while it's running (I had a friend operate the AC switch while I listened at the front). On the pump, the smaller of the two pipes will heat up in seconds while the other remains pretty much unchanged. The two pipes along the bulkhead do not display the same difference, they're very similar in temperature. Can you read anything into this? The blend motors work to a certain extent, as I get very hot air if I increase the temp to "HI", but it could be they won't go all the way in the opposite direction.
I appreciate the help.

Henrik
 
Datatek said:
With the engine running, check the 2 aircon pipes, one should get very hot, the other cold. If they do not, either gas has gone AWOL or the compressor clutch is slipping. The clutch will not engage if there is no or insufficient gas pressure.
Click to expand...

On mine you can clearly see condensation on the cold pipe when the AC is on.
 
Henrik97 said:
Hi,
Ok, so I performed the checks above. Pump is definitely engaging, as I can hear it kicking in and the pumping noise it makes while it's running (I had a friend operate the AC switch while I listened at the front). On the pump, the smaller of the two pipes will heat up in seconds while the other remains pretty much unchanged. The two pipes along the bulkhead do not display the same difference, they're very similar in temperature. Can you read anything into this? The blend motors work to a certain extent, as I get very hot air if I increase the temp to "HI", but it could be they won't go all the way in the opposite direction.
I appreciate the help.

Henrik
Click to expand...

I think you need to get a gauge on it to see how much gas is in the system.
 
stjohnsmythe said:
I think you need to get a gauge on it to see how much gas is in the system.
Click to expand...
I'm not saying you're wrong, but someone else said that a lack of gas will throw a pressure switch, which in turn would keep the pump from engaging.? As the pump is clearly running, I take that as a strong indication that there is at least enough gas that the system is operating, thus I should expect some cooling effect. To me it doesn't seem to cool the air whatsoever.

Henrik
 
Henrik97 said:
I'm not saying you're wrong, but someone else said that a lack of gas will throw a pressure switch, which in turn would keep the pump from engaging.? As the pump is clearly running, I take that as a strong indication that there is at least enough gas that the system is operating, thus I should expect some cooling effect. To me it doesn't seem to cool the air whatsoever.

Henrik
Click to expand...

It still sounds like lack of gas, the compressor will run down to quite low pressure. However, you need to be sure that the compressor is actually turning and not just the clutch assembly.
Of course, if the HEVAC blend motors will not go down to cold that would also give you warm air but as you said the pipe does not get cold you can leave that for the moment.
 
Last edited:
Datatek said:
It still sounds like lack of gas, the compressor will run down to quite low pressure. However, you need to be sure that the compressor is actually turning and not just the clutch assembly.
Of course, if the HEVAC blend motors will not go down to cold that would also give you warm air but as you said the pipe does not get cold you can leave that for the moment.
Click to expand...
Ok, so you're saying that one of the pipes should get properly cold? It certainly doesn't so that would put the fault somewhere in the refrigeration system. I will take it back to the garage that did the refill. They should have done a proper leak test, and if the system is down to a dysfunctional minimum after only a week, there is a leak there that they should have discovered. Hopefully they will re-test the pressure free of charge, and hopefully also refill again when the leak (if any) has been cured.

Thanks
Henrik
 
Henrik97 said:
Ok, so you're saying that one of the pipes should get properly cold? It certainly doesn't so that would put the fault somewhere in the refrigeration system. I will take it back to the garage that did the refill. They should have done a proper leak test, and if the system is down to a dysfunctional minimum after only a week, there is a leak there that they should have discovered. Hopefully they will re-test the pressure free of charge, and hopefully also refill again when the leak (if any) has been cured.

Thanks
Henrik
Click to expand...
If it is low gas pressure, the most likely cause is the condensor although the pipes have been known to develop pin holes.
One pipe should be very cold to touch, the other very hot when it has been running for several minutes.
 
Datatek said:
If it is low gas pressure, the most likely cause is the condensor although the pipes have been known to develop pin holes.
One pipe should be very cold to touch, the other very hot when it has been running for several minutes.
Click to expand...

Thanks,
The condenser is brand new, so I suspect it's probably a pipe or a valve if indeed there is low pressure. Off to get it tested now. Should the fans on the condenser run at all times, or will they switch on thermostatically?

Henrik
 
Pin hole in HP pipe. Pressure must have dropped further overnight as well, because today the compressor failed to engage. Thank you all, at least now I know what I need to replace.

Henrik
 
Henrik97 said:
Pin hole in HP pipe. Pressure must have dropped further overnight as well, because today the compressor failed to engage. Thank you all, at least now I know what I need to replace.

Henrik
Click to expand...

Glad to hear you're getting it sorted. It's really annoying when the AC doesn't work!
 
Henrik97 said:
Hi,
Ok, so I performed the checks above. Pump is definitely engaging, as I can hear it kicking in and the pumping noise it makes while it's running (I had a friend operate the AC switch while I listened at the front). On the pump, the smaller of the two pipes will heat up in seconds while the other remains pretty much unchanged. The two pipes along the bulkhead do not display the same difference, they're very similar in temperature. Can you read anything into this? The blend motors work to a certain extent, as I get very hot air if I increase the temp to "HI", but it could be they won't go all the way in the opposite direction.
I appreciate the help.

Henrik
Click to expand...
Its just low on gas,there is enough to make the trinary switch stay closed,but not enough to make it go cold.You need to get a sniff test done - usually leaking condensor....
 
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