Diagnosing and bulletproofing you A/C

[Reinsch]

Hello owners!
 
I thought I will write little article about Air Con (A/C) system on D as it is not the best design from electrical point of view. I will focus on electrical part as I'm Electrical Engineer working in automotive, so I know how it should be done properly.
 
Let's assume that your A/C system is filled with gas to correct pressure, engine is running, but no cold air is coming from vents, neither compressor is kicking in. I assume also that your fuses and relays are OK.






I suggest diagnosis in reverse:
 
1. Your compressor is not kicking in when you turn on A/C on (engine running, your fan at speed 1 minimum). That can be easily diagnosed - your compressor pulley is not engaging - this can be seen/heard.
To check if fault is with compressor (electromagnetic clutch) you disconnect RED wire that is on top of it and bypass it straight to +12V on your battery. Good practice is to use wire with fuse (in this case I would use 15-20A fuse and 1.5mm^2 wire) as in case of short on your clutch you will blow fuse, not melt wire!
 
REMEMBER TO SUPPLY POWER TO COMPRESSOR ONLY FOR FEW SECONDS! If you leave power permanently system will generate too high pressure and pipe will explode and release gas! You doing this only for diagnostic purpose. When A/C is on, compressor goes on and off all the time to keep certain pressure! It is not working all the time.
 
 
If you compressor is working once you supply power, it means problem is somewhere else. If compressor is seized you will see some serious shit happening with your belt, so be prepared (Always were adequate protection, in this case Safety Glasses)!

Once you done with diagnosing, remember to reconnect wire to original terminal!
 
2. Low pressure switch is your next suspect! Why? Unfortunately it is related to overall system design. When you energize compressor clutch, there is huge current spike as electromagnetic clutch is a big coil. This is causing sparking on all contacts (working contacts) all way down starting with your A/C Instrument Panel mode switch, through pressure switches. Sparking is causing contacts corrosion which after X amount of cycles will stop conducting current and results in your A/C not working at all. I would like to believe that whole system was designed to be operating witch such current spikes, but I have my doubts. To make it bulletproof you can make one small improvement that will let you forget about A/C electrical issues, but I will talk about this on the end of my post.

Now let’s go back to low pressure switch:



 
 
This switch is in open state when there is too low pressure in system. When pressure is correct, it should be closed.
Disconnect wires from it and check terminals for corrosion. Check with multimeter if switch is closed state (Remember, I assumed on beginning that you have correct gas pressure in system) . If switch is showing open state, then there is possibility that :
a) your gas pressure is too low to operate and you need to re-gas it (my assumption was wrong! You did not check it in first place! )
or
b) your pressure switch is faulty!
This can be replaced even with gas in system, however sometimes valve might be stuck and when you will be removing it, it will release some portion of gas with oil (ON YOUR FACE!) so please use all protective equipment like safety glasses/mask to cover your face and gloves. I would not remove it until you have replacement.
 
If you sure that your gas pressure is correct (as your system was just regased and checked for leaks!), you can short that switch and check if your compressor will kick in (engine running! fan speed 1 minimum). You short it using fuse (15A-20A). Basically, push on connectors on fuse. If it starts, you got faulty low pressure switch. Shorting this switch is only dangerous if you have no gas/oil in system as you will seize compressor. Remember, you are shorting this only to diagnose the system.
 
If switch is in closed state then go to next point :
 
3. High pressure switch
 

 
This switch is normally in closed state. Will be open once Air Con system will reach some certain value (preventing your system from blowing up. That is why in section 1. I warned you about not running your compressor for more than for few seconds as by-passing this switch is dangerous for longer than few seconds).
Diagnosis - remove connectors from switch and check for corrosion. Check using multimeter if switch is showing closed circuit. If no and you know that your gas pressure is correct you can short connector for few seconds using 15A-20A fuse to check if your compressor will kick in. If it will kick in, you got faulty high pressure switch. If nothing happens, go to next point.
 
4. A/C Panel
 
 
 
Your MODE SWITCH contacts might be worn due to sparking, as I said before, whole load to compressor goes through switches. Here is example of contact corrosion:
 

 
That deposit on your contacts prevents conduction. Good thing is that this can be rescued with some contact cleaner and really fine sand paper (800+). Removing HVAC panel takes a bit of time, so I would leave it for the end as I did in this tutorial.
Once all those elements are checked and in working condition your system should be in working order, unless wiring is damaged.

To diagnose that you will need multimeter with buzzer option to “ring” wires. If you own a DeLorean you possibly have wiring diagram, if not, it can be easily found on the internet.  Here is snapshot of important bit:




High pressure switch is between number 90 and 91 where you have a bump on diagram. Not sure why it is not marked there.

To make system bulletproof from electrical point of view you need to make little upgrade. Basically, you need to introduce a relay that will take a load from switches contacts. It can be added in the cabin or in engine room. Decision is up to you.

Cabin option: you will need to find wire in passenger legroom going back to compressor. That wire will control relay. On top of that you will have to get +12V and Earth, so system can work. Remember that your +12V can’t go straight from battery. You need to introduce fuse (I suggest 15-20A fuse and 1.5mm^2 wire). Earth can be local or straight from negative post of battery. You will have to fix your relay somewhere next to HVAC. You can use relay/relay base with fixing point or introduce relay box (this will help to soundproof relay cycling sound).

Engine room option: you will have to disconnect compressor flying lead and extend wire long enough to reach your relay (+ return wire to energize compressor clutch). This wire will be controlling relay. As in cabin option, you will have to get +12V and earth, so system can work. This solution is for “purists” as does not involve cutting OEM wiring and can be reversed by disconnecting upgrade kit (BUT WHY WOULD YOU WANT THAT?!), however relay/relay box will be visible in engine room.

Your circuit should look like this after modification:

Remember to put your relay in dry place or introduce a relay box to cover it when exposed to moisture. Don’t be cheap and invest in relay base. In case of relay fault, replacement will be easy.

If you want go step further you can get a relay with fuse. However this can be only used next to battery or when you connecting to already fused line. Reason is that if your wire shorts to ground before this fuse, it will melt wire/boil battery as there is no protection on that portion.

I hope that somebody will find this short article helpful. Unfortunately, I don’t have photos of switches locations (I do not own DeLorean yet, but worked on them).
I bet somebody will upload them under my post... (be that guy!)
If you have any doubt, think there is mistake in what I wrote, please let me know. I will try to explain more or correct my mistake.


Remember, this tutorial describes only electrical part of A/C system. It assumes that mechanical part is in working order.

kind regards,
Marek

[Rissy]

Nice write up!

A/C is an area i've paid very little attention to, simply because my system has never worked or even been gassed under my ownership. That's something I very much want to fix within the next 2-3yrs. I'm not sure right now which way i'm going to go, but I have two options.

1. Try and get my old R32 system up and running again
2. Rip it all out and replace with an R134a system

I've not decided which yet. Arguably, R32 is more efficient (cooler car), but it's more of a headache to deal with compared to just making it the same as modern cars.

[Chris Williams]

Nice write up Marek, thank you for doing that I'm sure it will help many an owner with the A/C systems.

Chris, I know you and I spoke about this before and I know we don't always agree! However since I swapped my system over to R134, draining all the oil out of the system and replacing the condenser & Accumulator (both were broke) I know you told me the gas would leak out through the OE hoses (and you were probably right) but it did last three years before I have had to have the gas topped up.
Not a perfect situation but if I can get 3 years between top-ups then that will do.
Chris

[Reinsch]

Hi Rissy,
It will be rather hard now to get R32.
If you system was not in operation for so long it possibly has moisture inside and is corroded. Such contamination can block orifice tube. Furthermore accumulator has some filters that are catching all humidity from gas, after so long (not sealed circuit) it is possibly full and blocked. On top of that you have all dry and old seals.
I would think you should bin in all, so you do it once... If you do it winter time it should be cheaper as those A/C guys are not so busy.

Chris,
It is recommended to drain and re-gas A/C system every 2 years. It helps to remove moisture and replace oil.
Gas is escaping in rate between 10-20% per year even in modern cars. It is simply normal.

kind regards,
Marek

[Rissy]

(19 Jun 2017, 20:36)Chris Williams Wrote: Chris, I know you and I spoke about this before and I know we don't always agree! However since I swapped my system over to R134, draining all the oil out of the system and replacing the condenser & Accumulator (both were broke) I know you told me the gas would leak out through the OE hoses (and you were probably right) but it did last three years before I have had to have the gas topped up.
Not a perfect situation but if I can get 3 years between top-ups then that will do.

Chris, It's not that you and I disagree, it's just that because the two systems are not chemically compliant, it means you have to do a thorough job at boiling off and removing ALL traces of the old oil and stuff embedded in the hose from years of R32 and oil exposure. The reason being that mixing those with the Esther oil (I think it is - i'm a bit rusty) and the R134a makes an acidic formula which then proceeds to eat away at your A/C components from the inside out. Maybe your system was flushed pretty well, and that's why it seems to be ok. The reason you're having to regas every few years is down to the old R32 compliant hoses not fully holding the R134a gas, so it escapes over time due to the molecules in R134a being smaller than R32. As you've been doing, that's just something you have to deal with, even if you're system isn't eating itself.

(20 Jun 2017, 08:12)Reinsch Wrote: Hi Rissy,
It will be rather hard now to get R32.

I'm aware of this, but when I say stick to my old R32 system, I'm meaning flushing it through, and using the R32 drop in replacement, RS34, which should still work with the hoses and the compressor etc (without them being eaten from the inside out). As you say though, i'd probably still need a new orifice tube, and dryer (accumulator) to make the whole lot work again since mine has been open to atmosphere for years (i've close it off now, but i'm sure it's too late - the initial damage will already be done). It's be a good opportunity to swap my old V1 dryer for the later, better, V2 dryer anyway...

[Chris Williams]

Quote:Chris, It's not that you and I disagree, it's just that because the two systems are not chemically compliant, it means you have to do a thorough job at boiling off and removing ALL traces of the old oil and stuff embedded in the hose from years of R32 and oil exposure. The reason being that mixing those with the Esther oil (I think it is - i'm a bit rusty) and the R134a makes an acidic formula which then proceeds to eat away at your A/C components from the inside out. Maybe your system was flushed pretty well, and that's why it seems to be ok. The reason you're having to regas every few years is down to the old R32 compliant hoses not fully holding the R134a gas, so it escapes over time due to the molecules in R134a being smaller than R32. As you've been doing, that's just something you have to deal with, even if you're system isn't eating itself.

Fair enough, I could not remember the full conversation but I do recall most of it now you remind me. I don't know enough about A/C and the above so am happy to agree with what you have wrote. I will keep you up to speed if and when it fails so at least it gives an idea of how long it will go.
Chris

[Chris Hawes]

It was two years ago via http://www.deloreans.co.uk/forum/showthr...p?tid=5071 that I referenced the article that Marek has just published.  I've now added the photos to the above article and below:-

Chosen location for aircon relays in an automotive rated enclosure:-




Cover removed


I suspect it was a lack of time/development as to why the cars didn't have relays incorporated into the aircon circuit.  This is a very much an upgrade that should be on any DeLorean to improve the longevity and reliability.  If not the various switches are all having to handle the loads that the relays can now handle!

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Rissy, I'm confused.  Stock DeLoreans were designed/setup with R12 systems but you're referencing a difference gas type.  Is/was Lex modified beyond stock to run R32?

My car used to go years like ChrisW between gas refills but now its less than three months.  It has a really slow leak which has been undetectable with dye testing.  I will in the next few years be doing a frame off job and at that point go for a new set of R134a rated hoses to ensure longevity.

My wife's 2006 car we've had for around five years.  It has never needed to be re-gassed, still blows cold and just goes to show how a well specced, designed and engineered system can go on and on and on.  The car doesn't drip any fluids either...... and is about to hit 100,000 miles.

[Rissy]

Ah yes, sorry, you're right. Replace all of my comments above with R12 instead of R32. I've been dealing with an old freezer lately and obviously got R32 stuck on the brain! Lol!

I also should have said RS24 not RS34! But looking it up, it seems now even RS24 has been superseded...

I told you I was rusty! Lol!

[Chris Williams]

Quote:The car doesn't drip any fluids either...... and is about to hit 100,000 miles

Ha, you should see the underneath of my yellow Transit Custom. Water flows from the A/C lost count of the number of people that have pointed out my van's leaking fluid! it's that bad it runs across a car park!
Chris

[Rissy]

(21 Jun 2017, 20:34)Chris Williams Wrote:

Quote:The car doesn't drip any fluids either...... and is about to hit 100,000 miles

Ha, you should see the underneath of my yellow Transit Custom. Water flows from the A/C lost count of the number of people that have pointed out my van's leaking fluid! it's that bad it runs across a car park!
Chris

Are you sure that's not just condensate from the A/C working on a hot day? It's normal if so. You should see some of the trucks used around the shipyards in S.Korea! They leave pee puddles everywhere they stop off for a few minutes. The condensate literally runs out of the bottom of them!

[Chris Williams]

Quote:Are you sure that's not just condensate from the A/C working on a hot day? It's normal if so. You should see some of the trucks used around the shipyards in S.Korea! They leave pee puddles everywhere they stop off for a few minutes. The condensate literally runs out of the bottom of them!

Oh yes it is that I was just making a point how bad some are (or good) at doing the job depending on your point of view!
Chris

[Dangermouse]

(20 Jun 2017, 08:12)Reinsch Wrote: Chris,
It is recommended to drain and re-gas A/C system every 2 years. It helps to remove moisture and replace oil.
Gas is escaping in rate between 10-20% per year even in modern cars. It is simply normal.

I'm not sure who would recommend this apart from AC gas manufacturers   It's a non-DIY task where you must pay a licensed professional to capture and refill the system.

Presently living in the south USA, I use car and home AC for probably 6 months of the year. The norm is to ignore the AC until you notice it isn't as cooling as well as it should and then get it topped up. I am running 4 German cars ~10 years old and the AC is fine and is un-touched. My house is ~20 years old and I can tell one of the systems is underperforming, However I can't face bringing an AC guy as there will be lots of tutting about the age of the system and suddenly it will stop working and they won't be able to get parts and that'll be $15k for a new one thank you very much, Sir.

What is recommended is to cycle the AC once a month in winter to keep the compressor etc. lubed internally


and yes, all my cars deposit condensate on the ground. As does the house. That is the "conditioning" part of Air Conditioning  - removing the humidity from the air.



but as I have said elsewhere, great post Marek

[Chris Williams]

Quote:What is recommended is to cycle the AC once a month in winter to keep the compressor etc. lubed internally

Will second that one, though I always advise more often (once a week) but time flies!
Chris