mx5cartalk.com

I'd search for it, but I can't be bothered

As stated, it seems my air con isn't cooling me any more. What I wanted to know was is there a way I can fault find it myself to see whether it actually is out of gas or whether it's some other issue.

The symptoms, as such, are that the air con button still works, but I don't get any cold air, nor do I get the usual rise in revs & power drain to tell me that the aircon is actually going.

i think the first obvious answer is to take it to an autoelectrician, most of them do airconditioning regassing. get them to check it out for you.

from the sounds of it marcus, its out of gas.

sliq wrote:i think the first obvious answer is to take it to an autoelectrician, most of them do airconditioning regassing. get them to check it out for you.

from the sounds of it marcus, its out of gas.

I have no doubt I'll need to take it to an auto electrician at some stage. My point is more to see if I can do some preliminary diagnosis so when I see an auto electrician I can go "yeah, it's just out of gas because I've checked this this and this, therefore it can only be that".

Wun,

If you have a multimeter, start going through the system and check for power.
If at the low pressure switch you should have power on both sides if power to only one side you are low on gas. This switch prevents the compressor working with low gas and lubricant to protect compressor.
You will have to use a wiring diagram and spent time testing everything.

Have fun.


Terry

I'm not sure what model you own there, but here are few basics you can test for yourself ;

I assume from your post that you have turned the A/C Switch on and the Cooling Fan is actually Blowing Air? if yes then we can go from there ...
1) Take a look over all visible air conditioning High and Low pressure tubing (aluminium) and also get a good torch and check your Condensor in front of the Radiator - look carefully for Oil especially on the connections and the Reciever Dryer (it looks like a Coke Can located in the engine bay) although it's not red - just alloy.
Oily residue is a good sign that you have lost your Gas charge, you only have to lose 5% of your charge to have a significant affect on your cooling.

2) On most Receiver / Dryer units (at least on NB's) you will see a plug which should have 2 wires - this plug is attached to a Pressure Switch within the unit. If you have a Multimeter or test lamps test for a circuit here first, the easy way is to pull the plug out then test continuity across this pressure switch. If you are not electrically blessed then you can go to this next step.

3) You should check if there is any Gas at all in your A/C System, on the Receiver / Dryer ther should be two Caps, Unscrew one of the 2 Caps preferably the one marked "HP" - it looks like a Tyre Valve, very quickly press down on the valve inside the removed cap and if there is any charge you will hear Gas escaping. If you hear nothing at all then DO NOT PROCEED with the next step as you have no gas charge at all (take it for repair as you have a major leak).

4) You will need some small diameter wire or a Paper Clip to short these two wires.

5) Once you have bridged (shorted) these wires, start your engine leaving the bonnet raised and the A/C Fan running then lean in and hit your A/C Button - if you are low on Refrigerant Charge the Compressor will kick in and run; BUT turn it off quickly as it can cause damage to the compressor if the charge is too low - generally the vast majority of systems develop slow leaks from dried "Ö" Rings and a system can be locked out by the pressure switch with only 10% gas loss, you can avoid this by regulary running you A/C System over winter months.

That is a quick and basic way of checking - if you are good with wiring circuits and the use of a Multimeter then I'd suggest testing the circuits to ascertain a pressure switch lockout.

If this test is succesful you need to look for leaks, a big problem with MX5's is stones hitting the Condensor - I've already replaced one for this reason ..... now I have a Grille.

i think the condensors usually have a sight glass in them, similar to some non maintenance car batteries. something like green in the sightglass for gas is present or totally black for no gas?

if the A/C has been recharged at some point after the car left the factory, the person who did the recharging may have used the A/C gas with the leak tracing dye that shows up under UV light. got a UV light?

& apparently the A/C system is meant to be used for at least 10 minutes every fortnite, keeps the seals inside the compressor lubed & stops them drying out which cracks them & then the gas leaks out. expensive repair job.

tbro wrote:Wun,

I haven't even seen him in here. I like how you assumed it was him though

Thanks for the advice guys. Fortunately enough, I would say I'm fairly electrically minded (didn't do a computer engineering degree and come out of it not electrically minded) so I'll give all your suggestions a crack on the weekend. I'll dig up my wiring diagrams that I've saved off somewhere and see how I go.

I haven't run the aircon for ages, so that's more than likely what's happened. Hopefully it won't be an expensive jobby to fix. Will have to remember to run the air con every now and then once it's fixed up to keep it from crapping itself. Especially since summer's just around the corner when I actually use the air con.

PS keep the suggestions flowing too, if there are any more. The more I know the better...

If you have a Multimeter, Wiring Schematics and 15 minutes then you are going to be just fine

marcusus wrote:

tbro wrote:Wun,

I haven't even seen him in here. I like how you assumed it was him though

If it was Wun the post would be about how to remove the A/C

The fact that the button has no effect would make me think that it is electrical. If the system had no gas I assume the compressor would still be dríven when you push the button and there fore you would feel the power loss etc. But I dont really know anything about this. Great advice from others.

If the system had no gas I assume the compressor would still be dríven when you push the button and there fore you would feel the power loss etc

You would assume this but as stated in an earlier post the A/C manufacturers in their wisdom have fitted high and low pressure switches to avoid damaging expensive critical components if the gas pressure is outside set ranges.

Garry wrote:

If the system had no gas I assume the compressor would still be dríven when you push the button and there fore you would feel the power loss etc

You would assume this but as stated in an earlier post the A/C manufacturers in their wisdom have fitted high and low pressure switches to avoid damaging expensive critical components if the gas pressure is outside set ranges.

Oops, I did read that but it went right over my head. Thanks makes sense.

Would it be possible to plug in a diagnosis device to see if this switch has been activated

Yeah my AC is also week and not cold enough to make me comfortable.
Not interested in a topping up the gas unless they use Hydrogen.
I would like to remove the AC one day I have the smaller lighter belt, would be a great summer project.
I dont mind being hot and bothered because sweat evaporates = less weight.

MX5CHIC wrote:.... here are few basics you can test for yourself ....

Fantastic troubleshooting guide there MX5CHIC. OKIBI this needs to be saved somewhere in the technical guides section.

Cheers,
Alf

prince of liteness wrote:Yeah my AC is also week and not cold enough to make me comfortable.
Not interested in a topping up the gas unless they use Hydrogen.
I would like to remove the AC one day I have the smaller lighter belt, would be a great summer project.
I dont mind being hot and bothered because sweat evaporates = less weight.

Hydrogen??!?! are you kidding? hhaahha

MX5CHIC wrote:I'm not sure what model you own there

I always forget to mention what model I have... for some reason I just assume everybody knows
It's an NB8A.

MX5CHIC wrote:I assume from your post that you have turned the A/C Switch on and the Cooling Fan is actually Blowing Air? if yes then we can go from there ...
1) Take a look over all visible air conditioning High and Low pressure tubing (aluminium) and also get a good torch and check your Condensor in front of the Radiator - look carefully for Oil especially on the connections and the Reciever Dryer (it looks like a Coke Can located in the engine bay) although it's not red - just alloy.
Oily residue is a good sign that you have lost your Gas charge, you only have to lose 5% of your charge to have a significant affect on your cooling.

Yes, fans are blowing air, yes air conditioning is turned on (valid questions... sometimes people do silly things).
Looked over all the tubing and receiver/dryer and couldn't see anything liquid or leaky along the tubing. I'm a bit lost as to where to find the condensor though. When you say in front of the radiator, do you mean it's forward of it essentially in the nose of the car, or do you mean on the engine side? I'm guessing it's the nose side because the only thing on the engine side was the fan and some motor thing attached to the fan, which I'll assume is the fan motor. Either way, what should I check on the condensor (when I find it)?

MX5CHIC wrote:2) On most Receiver / Dryer units (at least on NB's) you will see a plug which should have 2 wires - this plug is attached to a Pressure Switch within the unit. If you have a Multimeter or test lamps test for a circuit here first, the easy way is to pull the plug out then test continuity across this pressure switch. If you are not electrically blessed then you can go to this next step.

Took the plug out. Tested the voltage across the plug (obviously there's no point testing across the receiver/dryer because that's the device that needs the voltage... it won't be putting anything out) and confirmed it was working. Was getting something like 11v across it when the air conditioning was turned on and 0v when the air con was off, so that all looks alright.

MX5CHIC wrote:3) You should check if there is any Gas at all in your A/C System, on the Receiver / Dryer ther should be two Caps, Unscrew one of the 2 Caps preferably the one marked "HP" - it looks like a Tyre Valve, very quickly press down on the valve inside the removed cap and if there is any charge you will hear Gas escaping. If you hear nothing at all then DO NOT PROCEED with the next step as you have no gas charge at all (take it for repair as you have a major leak).

Pressed the valve release under the HP cap. I was getting gas escaping so it seems that there's still gas of some sort in there. It seemed like a fairly strong bit of pressure coming out of there, although that's only an observation on my part. I have no idea whether that means anything at all.

MX5CHIC wrote:5) Once you have bridged (shorted) these wires, start your engine leaving the bonnet raised and the A/C Fan running then lean in and hit your A/C Button - if you are low on Refrigerant Charge the Compressor will kick in and run; BUT turn it off quickly as it can cause damage to the compressor if the charge is too low - generally the vast majority of systems develop slow leaks from dried "Ö" Rings and a system can be locked out by the pressure switch with only 10% gas loss, you can avoid this by regulary running you A/C System over winter months.

This is what I have yet to try because I'm a little confused with the instructions. What should I be shorting? Should I be shorting the terminals on the receiver/dryer? Knowing that I've confirmed that the wiring from the A/C button to the loom generates a voltage across the plug, essentially plugging the plug back in and pushing the A/C button should have the same effect as shorting across the terminals of the receiver/dryer yes?

Now, assuming that I did short the wires/terminals/whatever and the compressor kicked in, what should I be looking for? Should I be checking for cold air coming through, or should I just be confirming that the compressor runs at all?

MX5CHIC wrote:That is a quick and basic way of checking - if you are good with wiring circuits and the use of a Multimeter then I'd suggest testing the circuits to ascertain a pressure switch lockout.

If this test is succesful you need to look for leaks, a big problem with MX5's is stones hitting the Condensor - I've already replaced one for this reason ..... now I have a Grille.

So is the pressure switch essentially that voltage drop that's being applied to the receiver/dryer?

Thanks very much for the advice everyone's given so far. If I can get a bit more info I'll give it another looking over tomorrow, but so far it seems like I'll be paying a visit to the mechanic to see who he recommends for electrical/air con work...