A/C system problems

[larsmhh]

Hi!
For a long time I was just reading the threads, but now I have a problem that in Germany is not so easy to solve (or better: to identify).

I did have the original Sanden climate compressor installed on my early Delorean (#1550), which was leaking from its shaft.
This spring the A/C system was absolutely empty.
At DeloreanGo I bought the "new improved UAC climate compressor", a new dryer and one new climate hose (from the orifice tube to the condenser).
I also fitted the high pressure switch/console with the pressure relief valve - my car did not have this security system, but just a factory fitted electric bypass plug for the high pressure switch.
My old system was already changed from R12 to R134a about 7 years before and - until the compressor leak - it was working fine.

The system was filled up with the right amount of PAG100 oil (185ml) and 920ml of R134a freon gas.
It is cooling very well, the compressor is working silently and strong (the air is getting 3°C or 37°F cold), but when I drove the car now for a longer test drive there was cool but less and less air comming out of the vents - first I did not know why but with help of Googe AI I realized, that the cooling was so strong that the evaporator was frozen so much, that the air was unable to pass it, resulting in no air comming out of the vents.
I was also instructed (from the AI) to watch for the cycling of the compressor - which did not take place. The compressor is just working all the time - and that is the problem of my system.

I was thinking of a defective low pressure switch (which I changed as well with all of the work done this spring).
I turned the adjustment screw (which should have been turned counterclockwise 1 full turn when installing it to change the setting from R12 to R134a) clockwise and clockwise and clockwise and just before the end of the thread was reached, the compressor started cycling. Unfortunately it did not cycle as ist should (35 - 40 seconds on, 15 seconds off,...) but 15 seconds on, 2 seconds off.
Whatever I tried, I did not get it to work properly. I also changed the low pressure switch back to my old one (which I kept) - but with exactly the same results.

So I don´t think the low pressure switches are both bad, but I don´t hava a clou, what is wrong on my car or where to start the diagnostics.
I ordered a low pressure gauge (for the blue A/C-port) but it has not yet arrived - so I can not yet tel you about he pressure in the system. I hope in 2 - 3 days it arrives and I can read the pressure on the system for more information/conlusions...

I asked the guys in the A/C garage, who filled up the system but they do not have any ideas, where to start to search for this problem on a Delorean.
In the Internet it is said, maybe it could be the orifice tube (that I did not change :bawling: ) or it could be to much PAG oil, or to much or less Freon gas...

Hoping to get advice from you where to start and what to do...

I was searching this forum for my fault pattern but did not really find relevant information.

Thank you in advance and best wishes from hot Germany (it is up to 90°F today),

Lars :)

[Bitsyncmaster]

You would be looking for the compressor to shut off on anything below 30 PSI on the low side. If you still get ice, set that higher. You also want to verify your drain tube is working. I had to remove the original drain tube and make one without that restriction elbow.

[larsmhh]

Hi David!
Thank you for your reply. I also think that a real discussion about the problem on my car is only possible once the gauge has arrived and I can give you the pressure measurements.

About the drain tube: The drain tube is continuous, because there is a lot of dripping water when the A/C is working.
This was one of the criteria for the Google AI to come to the point that the evaporator was an ice blog - after this incident there was a real big amount of water comming out of the evaporator (melting ice block)...

I hope the gauge will arrive soon so I will know about the pressure levels soon.

Kind regards,

Lars :)

[dn010]

For what it's worth, I had two low pressure switches, right in a row, that were bad right out of the box. The quality of parts sucks these days.

[larsmhh]

Hi!

I found the time to work on my Delorean.
The gauge did measure 0,0 bar (or psi) - nothing.
I thouht, the Schrader ventile could be faulty, but I could easily press it with the tip of a screwdriver.
So I asked the Google AI for help and after a little discussion it was sure that the orifice tube would be clogged.
I was absolutely sure to find an orifice tube as good as new in the tube, because it was changed 8 years ago and the Delorean was more standing around than driving since then.
But that was not the case:
There was a lot of black sticky grease. When I tried to pull the orifice tube out with a special tool (orifice remoover from Hella Behr), I tore off the head.
Finally (after one hour of work I got a red-hot screw melted and turned into the orifice and with pliers pulled out of the aluminium tube...
Here is a photo.
I did find the dirt only on the outer side (looking towards me) of the orifice tube. I cleaned it all up physically with a small metal hose brush (since AI told me not to use any brake cleaner, Isopropanol, ...) and inserted a new orifice tube.

Now it is time to fill the a/c with R134a again - and finally test it.

I hope that it will now be running fine...

I will report as soon as I have the results.

Bye, Lars :)

[Bitsyncmaster]

That black sticky grease is probably caused by not flushing the system of the old oil when converting to R134a.

[larsmhh]

Hi David!

I do also come to this conclusion. I am also not sure, if the orifice tube was changed 8 years ago when the system got converted.
It was so much force and heat (and sweat) necessary to get the orifice tube out - I think it must have been sitting there since 1981...
I did not do the R12/R134a conversion by myself, but in a professional garage. So I can just hope they did what I paid them for...

But the system was running when I tried to sell my Delorean in 2024. Since nobody wanted to buy it, I decided to stay with it in late 2025 (and never will sell it again) the system was empty and the compressor leaky.
I do not know, how it was able to work properly up to 2024 with this blockage of the orifice tube, but it did!
Maybe the seal of the compressor gave up because of the blockage or because it was 43 years old - or both.
I bought a new compressor from DeloreanGo from a company called UAC (settled in the USA but producing in China).

Hoping for the best,

Lars :)

[David T]

When your car was converted to -134 they did not flush the system thoroughly of the original oil. You cannot mix the old oil and the new oil. Your condenser coil is now contaminated, that black goo gets burnt inside and is impossible to remove. The shop also overfilled your system with -134. When converting to -134 you must derate and charge with 10% refrigerant because of the higher head pressure. That's why you couldn't adjust the low pressure switch to get it to cycle.

To fix this mess you must now flush the evaporator coil with R-11, replace all of the hoses, the accumulator/dryer, the condenser coil and probably the compressor. If you don't want to use R-12 try to find R-414a or some other blended refrigerant. R-134 has too high a head pressure and you lose 10% of your cooling capacity. The shop that did this should do something for you about this, they should have done a better flush. We call that stuff "The Black Goo of Death".

[dn010]

Considering the conversion was done seven years ago, I doubt the shop that did this would do something about this.


The shop that did this should do something for you about this, they should have done a better flush. We call that stuff "The Black Goo of Death".

[larsmhh]

Hi!
I wanted to report how the story went on - and here it is:

Short version: The A/C in my Delorean is still not working propperly

Long version:
We refilled the A/C system with 920 g of R134a and doing this the system passed the 30 minute vacuum test.

After this the system did show the same results: Compressor is constantly running, no idling, no response on the low pressure switch (but if I unswitch it, the compressor stopps).
I also did not have any pressure on the blue (low-pressure) port near the compressor.

What to do next:
A garage sucked all the R134a out of the system again this morning.

Now my plan ist to test every tube and component of the A/C system separately.
I bought a special cleaning fluid and a pressure sprayer to get this done.
Hopefully one component will show an obstruction. Maybe it can easily changed, in the worst case it is the evaporator under the dashboard...
I also bought a bottle of N2 to get the system blown dry after the cleaning - this was described for the use of the cleaning fluid.

Then I will change the orifice tube a second time and the dryer for a new one, too.
Every O-ring of the connections I open will also be changed and then I will fill the system up with 920 g of R134a again.
I am already wondering, how much PAG100 oil I should add when the dryer is changed and all the tubes, the condensor and evaporator are cleaned out, but - depending of what has to be changed as well - this is a thing of the future...

What do you think of this plan? Maybe you have a better idea how to get this problem solved!?

Bye for now,

Lars :)

[Bitsyncmaster]

What is your high side pressure? Does the low side pressure go up after sitting? If not you do have complete blockage. Maybe your gauge is not opening the schrider valve

[dn010]

Sounds like you only have a gauge for the low side. You really need gauges for both the low and high side (manifold gauge) to see what's going on. I'd also get rid of any low pressure switch that has been tampered with (adjusted) and start with a new one before tearing everything apart. Was the air blowing cold during the latest attempt?

Also if you're trying to test the system while it's hot outside, the compressor not cycling at idle is normal depending on temp.

[DMC-Ron]

Hi!
I wanted to report how the story went on - and here it is:

Short version: The A/C in my Delorean is still not working propperly

Long version:
We refilled the A/C system with 920 g of R134a and doing this the system passed the 30 minute vacuum test.

After this the system did show the same results: Compressor is constantly running, no idling, no response on the low pressure switch (but if I unswitch it, the compressor stopps).
I also did not have any pressure on the blue (low-pressure) port near the compressor.

What to do next:
A garage sucked all the R134a out of the system again this morning.

Now my plan ist to test every tube and component of the A/C system separately.
I bought a special cleaning fluid and a pressure sprayer to get this done.
Hopefully one component will show an obstruction. Maybe it can easily changed, in the worst case it is the evaporator under the dashboard...
I also bought a bottle of N2 to get the system blown dry after the cleaning - this was described for the use of the cleaning fluid.

Then I will change the orifice tube a second time and the dryer for a new one, too.
Every O-ring of the connections I open will also be changed and then I will fill the system up with 920 g of R134a again.
I am already wondering, how much PAG100 oil I should add when the dryer is changed and all the tubes, the condensor and evaporator are cleaned out, but - depending of what has to be changed as well - this is a thing of the future...

What do you think of this plan? Maybe you have a better idea how to get this problem solved!?

Bye for now,

Lars :)

Lars,
In earlier times, with all the refrigerant removed, we would to pull the system down with a vacuum pump then close off the system and wait to see if it held the vacuum. If it didn't, we knew we had a leak. I understand the modern practice is to pressure test the system using inert gas (like dry nitrogen) rather than pulling a vacuum, because refrigerant lines under pressure more closely reflect the operating condition and a leak may occur under pressure that would not show up when in vacuum. In any event, the objective is to first insure you do not have a leak in the system before you recharge with refrigerant.
Ron

[David T]

Lars,
In earlier times, with all the refrigerant removed, we would to pull the system down with a vacuum pump then close off the system and wait to see if it held the vacuum. If it didn't, we knew we had a leak. I understand the modern practice is to pressure test the system using inert gas (like dry nitrogen) rather than pulling a vacuum, because refrigerant lines under pressure more closely reflect the operating condition and a leak may occur under pressure that would not show up when in vacuum. In any event, the objective is to first insure you do not have a leak in the system before you recharge with refrigerant.
Ron

There are several reasons to use pressurized Nitrogen for leak testing instead of pulling and holding a vacuum. BTW, if you do try the vacuum test and you see it goes up, you may not have any leaks but you ARE boiling out moisture. If you have a leak you are pulling air and moisture into the system. A vacuum is only 15 psi negative but you can pressurize to 100 psi positive with Nitrogen. Nitrogen is very dry so it helps to dry out the system. By getting to 100 psi you can find much smaller leaks. Although you cannot use a leak tester (they are looking for refrigerant and cannot detect Nitrogen) you can use an ultrasonic tester or leak test solution (soapy water with glycerine) to find leaks. If you can't see any pressure from the low side port you probably need to replace the shrader valve or the depressor on your hose is missing. All hoses have a specification for leakage per foot of hose. Because a Delorean has so much hose it has a higher than usual leakage rate. The newer barrier type hoses have a much lower leakage rate. Jumper the low pressure switch. Charge the system with the correct amount of refrigerant by weight after pulling a 500 micron vacuum for at least 1 hour. Check your pressures and then adjust the low pressure switch to get it to cycle properly with the motor at 1,000 RPM, a fan blowing at the radiator, cabin fan on high, mode switch on Normal, windows and doors closed. You should see a 20 degree drop across the evap coil. This is not rocket science but you do need to find a shop that knows what they are doing.

[dn010]

On top of all this you need to also figure out how much oil you have in the system. If you flush everything out, you need to take the compressor out, drain it and measure to see how much oil you need to add on top of that. Or you can discard the compressor oil and just add the proper amount of fresh oil which is what I would do in your case.

[Helirich]

If I understand this correct, you have a constant running compressor, but no pressure at the low side port. This is not possible. My guess is the shrader is clogged. When you say you tried a screwdriver at it, did it spray out Freon? Most guage hoses have an end that pushes the shrader and the other end does not have the protrudsion. Is there any chance you have the wrong end on the gauge?

When you say the compressor stops when un switched, are you unplugging the sensor or are you unplugging right at the compressor or just the panel switch? You need to do this at the sensor.

You need to get that low side guage working at a minimum. As Bitsy said, the compressor must shut off if the pressure goes below a certain level. If it never goes low, you have too much Freon or the compressor is not working good.

[dn010]

As Bitsy said, the compressor must shut off if the pressure goes below a certain level. If it never goes low, you have too much Freon or the compressor is not working good....OR it's hot as hell outside with less than ideal airflow over your condensor, and it's completely normal to not cycle.

[Helirich]

...OR it's hot as hell outside with less than ideal airflow over your condensor, and it's completely normal to not cycle.

You are right. I was not saying it must cycle. I ment that it must go low. I?ve had mine go down to 30 psi and not shut off because I think it set to go off at 25 or so. But if it doesn?t go down below 60, you got too much Freon or the compressor is not is bad.