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View Full Version : Heat & A/C Pointers on diagnosing A/C problems? Bringing to mechanic and want to bring parts.



DavidProehl
06-12-2011, 02:22 PM
The A/C on my car stopped working. It may have died on me sometime over the winter as this was the first time I've tried using it this year.

Not being an A/C expert and lacking any of the A/C tools needed to repair this, I'm planning to take it into my mechanic. I'm wondering if there are any suggestions as to how I could get an initial idea as to what might be wrong. Ideally I'd bring the car into my mechanic with any needed parts ready to go.

I've checked my #10 fuse, my fans blow when I switch over to A/C, but nothing colder than the vent. It seems like the most common issue is a leak, but is there anyway I can verify it is or isn't anything else, such a bad compressor, without A/C specific tools? As far as I know I'm still running the R12 stock setup.

I've been looking at a few of the recent A/C threads (http://dmctalk.org/showthread.php?209-Cooling-fans-and-AC) and it sounds like A/C issues can be one of the more challenging areas on this car when they happen.

Bitsyncmaster
06-12-2011, 02:27 PM
How many years has the AC been working for you?

When it was working was it really cold?

If you still have the original R12 then most likely you just need a little charge of R12. But if it was working very good and suddenly stopped than maybe a component when bad.

DavidProehl
06-12-2011, 02:35 PM
I bought the car in August of 2008, and it has been cold since then. The last time I used the A/C that I remember it working was September 2010. It always blew consistently cold, no variation in temp. It was never as cold as my daily driver, but plenty cold enough for me.

Typically R12 leaks happen gradually so I would notice it getting warmer over time right? But since I haven't used the A/C for 6-7 months it is possible it leaked out without me having a chance to notice.

Is my next step to take it in to have it recharged or is there a way I can verify if anything else went on me?

Bitsyncmaster
06-12-2011, 02:41 PM
If your mechanic is good with AC, he will know if it's low on R12. Then if not he should know how to locate the problem.

Does your compressor come on when you switch the AC on?

DavidProehl
06-12-2011, 02:45 PM
When I switch to A/C I hear the release of air as I turn the dial, but I don't hear the compressor kick on and off like I once did. Dumb question: Should it still behave like it would if the R12 is fully charged? If so, then there is a good chance I have a compressor issue.

stevedmc
06-12-2011, 03:04 PM
Go back their and see if your compressor clutch is engaging. First start the car and leave the AC turned off. Notice that the center of the AC pulley does not move. Now turn on your AC and go back there to see if the clutch engages. If the clutch engages the center of the AC pulley will be spinning.

If the clutch isn't engaging you could have low freon or a bad AC compressor. If the clutch only engages for a few seconds and then shuts off and back on then you are likely low on freon.

My AC had a small leak because a shop who converted it to r134a didn' tighten a connection to the accumulator. The low amount of freon was causing the compressor to not cycle. I simply tightened the connection, evacuated the system, and then vacuumed and filled it back up.

Now my compressor runs like it should and I am enjoying cold air again.

Let us know if the compressor clutch is engaging or not and we can help you from there.

Bitsyncmaster
06-12-2011, 03:07 PM
Your compressor will not switch on if your low on R12. That also will stop the cooling fans from switching on when the compressor switched on. You still get cooling fans running to keep the engine cool.

It could be an electrical issue not turning on the compressor. When a compressor goes bad it would still turn it on but be very noisy.

DavidProehl
06-12-2011, 03:42 PM
I started the car, then turned on the A/C and checked the center of the compressor pulley - no rotation. So I guess that means my clutch isn't engaging. It didn't start and stop, no movement at all. Also no loud noises. So I guess this means I am either very low on R12 or my compressor is bad?

Since the compressor is a $200 part it is probably worth recharging before ordering a new compressor.

Bitsyncmaster
06-12-2011, 04:00 PM
I started the car, then turned on the A/C and checked the center of the compressor pulley - no rotation. So I guess that means my clutch isn't engaging. It didn't start and stop, no movement at all. Also no loud noises. So I guess this means I am either very low on R12 or my compressor is bad?

Since the compressor is a $200 part it is probably worth recharging before ordering a new compressor.

Your compressor is probably good since you had good cooling last season. What kills the compressor is the shaft seal from not being used. Then it will leak at that seal. You should try to run your compressor every month or two but not running it for 6 months should not have hurt it. Most modern cars turn the compressor on with defrost so they they get used all year.

stevedmc
06-12-2011, 04:01 PM
Like you mentioned it sounds like you either have a bad compressor or simply low freon. You can perform a quick test on the compressor by jumping it to see if the compressor engages.

Look at your compressor and notice that there is a red wire running to it. This is where the compressor gets it power. When the system needs the compressor clutch to engage it sends 12v through the wire and to the compressor.

You can disconnect the red wire and run it directly to the starter post. The starter post is bolted directly to the fiberglass body and is between the wiring cover and your coolant tank.

What I do is use a length of wire and connect one end to the terminal. Then just start the car, turn on the AC, and connect the AC wire to the 12V. If the compressor is good you will hear a click and then see the inside of the pulley start to spin. Don't leave it connected for more than a few seconds. Running the compressor too long without freon in the system will burn it up.

Also, be careful with that 12v wire in the engine bay. You don't want it to get caught by one of the belts and you don't want to let it touch anything that is grounded. Sparks will fly if that wire touches anything grounded.

content22207
06-12-2011, 04:15 PM
Is my memory going bad, or did compressors from the vendors used to be significantly more expensive? I seem to remember them being around $300.

Bill Robertson
#5939

DavidProehl
06-12-2011, 04:21 PM
Thanks so much for the tips! I greatly appreciate it! I'll have to find some wire before I'm able to try that compressor check Steve mentioned. Either way, sounds like I should make sure my freon is fully charged.

Might be a topic for another thread, but I haven't been running the A/C in the winter because I haven't been starting the car during our sub-zero MN winters. This could be a direct result of that decision, but based on the pros/cons of starting vs no starting I've chosen not to start thus far.

stevedmc
06-12-2011, 04:22 PM
I believe Hervey is selling an SD508 with an accumulator for about $190. You have to ship him your old back plate and he does the swap. It sounds like a really good deal.

From what I read the SD508 is a little less efficient than the stock SD510. I have seen new SD510s on ebay starting around $150 but you don't get the accumulator and you have to swap the back yourself. One concern I do have with an SD510 on ebay is that you don't know the age of the part and many are Sanden clones.

Right now my compressor is fine but if mine stops working I am seriously going to consider replacing it with an SD510 just because I don't want to loose any cooling capacity. I wouldn't mind getting one of his larger condensers though.

stevedmc
06-12-2011, 04:39 PM
Shoot, I just checked and he sells the AC compressor by itself for $175. The nice thing about his stuff is you know it is new, vs questionable stuff on ebay.

Decisions, decisions...

Hopefully all you need is to evacuate, vacuum, and refill.

DavidProehl
06-12-2011, 04:46 PM
Steve - Just tried the test you recommended on the compressor. I ran a jumper cable from the post, started the car, turned on the A/C, then touched the other end of the jumper cable to the compressor wire for 1 second and the compressor came to life. That is a relief!

So hopefully this is a fairly cheap (in DeLorean terms) fix of a recharge. Thanks again everyone for the pointers!

stevedmc
06-12-2011, 04:49 PM
That is good news. We can walk you through some more troubleshooting if you want but you will need to buy a gauge at the least.

Are you still running r12?

DavidProehl
06-12-2011, 04:58 PM
Yes, I'm still running R12. I don't have any interest in doing the A/C recharge myself, so I'm not sure if it makes sense for me to invest in A/C gauges....what would the next step be in troubleshooting? Checking R12 pressure or lack there of? Since I know I'm taking it in it might not matter. If the two primary causes of non-working A/C systems are a bad compressor and low R12 and I now know my compressor runs, then I feel pretty confident that I'm low on R12. That level of confidence is good enough for me.

stevedmc
06-12-2011, 05:03 PM
Basically you need a gauge to hook up and see how much is in the system. If it isn't too low you would be able to top it off. If it is too low you will need to pull a vacuum and then fill it back up.

You can get a license for r12 easily but in my opinion r12 isn't worth keeping. I am licensed to buy r12 and I chose to convert to 134a for convenience.

Bringing it to a shop is probably a good idea though. It shouldn't cost much in terms of labor for them to check and fill it. What is going to cost money is the r12. Last year I bought r12 for $35 a can. I can imagine it costs even more this year.

r134a can still be found for less than $10 a can if you shop at places like Walmart and Dollar General.

content22207
06-12-2011, 05:22 PM
Buy a cheap R134 gauge and a low side adapter fitting (one of the ones that presses against the original schrader valve) -- that's all you need to check the level of freon. Should set you back less than $20. Screw the adapter on and look for ~100 PSI when the system is idle.

Don't forget to remove the adapter when you're finished, otherwise someone will mistakenly assume your system has been converted to 134.

Bill Robertson
#5939

Bitsyncmaster
06-12-2011, 06:26 PM
The gauge will only show you if your empty. You can't determine how much freon is in the system by reading the static low pressure.

FYI:
Just picked up 4 cans of R134a at BIG LOTS for $8.00 each. Just last year you could get it for $5. What caused the big price increase? Even Walmart is about $9.

content22207
06-12-2011, 06:58 PM
As long as your orifice tube isn't stopped up you can do all your A/C work through the low side. #5939 has never had a high side adapter.

Bill Robertson
#5939

stevedmc
06-12-2011, 10:31 PM
The gauge will only show you if your empty. You can't determine how much freon is in the system by reading the static low pressure.

FYI:
Just picked up 4 cans of R134a at BIG LOTS for $8.00 each. Just last year you could get it for $5. What caused the big price increase? Even Walmart is about $9.

The government is planning to phase out r134a soon. I suspect the price of r134a will continue to rise and the new stuff will be sold for around $5 a can to convince the public to start using whatever they come up with.

The government is doing the same thing with fuel in order to convince people they need electric and hybrid cars.

Chris4099
06-12-2011, 11:19 PM
HFO-1234yf is actually more expensive to make then R-134a. So until R-134a is no longer made and HFO-1234yf is produced in larger quantities, that probably won't happen. At least it will be close to a decade before the transition is complete and when it does HFO-1234yf is a drop in replacement for R-134a systems. As for fuel, I don't want to go political, but how can the government encourage hybrids through fuel prices when they use the same fuel as regular cars?

stevedmc
06-13-2011, 08:41 AM
HFO-1234yf is actually more expensive to make then R-134a. So until R-134a is no longer made and HFO-1234yf is produced in larger quantities, that probably won't happen. At least it will be close to a decade before the transition is complete and when it does HFO-1234yf is a drop in replacement for R-134a systems. As for fuel, I don't want to go political, but how can the government encourage hybrids through fuel prices when they use the same fuel as regular cars?

All it takes is some nice taxes on 134 to make it more expensive and most hybrids use less fuel than regular cars.

David T
06-13-2011, 10:46 AM
You should NEVER do any service work on an A/C system without monitoring the high side head pressures. If you do not monitor the high side you can overcharge the system, if the system has air you will overwork the compressor, have reduced cooling, and burn up the oil. You also take the chance of blowing hoses and the relief valve. Static low side pressure is no measure of the quantity of refrigerant, it can only tell you if the system is below the specified fill if you correct for ambient temperature. This is exactly what the the low pressure switch does. So if the system will only run if you jumper the low pressure switch, you are low on refrigerant. Low and empty are two different conditions. If you are only a little low it may be possible to "top off" or add enough to get he system to run. You still have leaks and will go "flat" again so the proper thing to do is to find and fix the leaks. Empty is BAD because the system will get air and moisture inside. Once that happens adding refrigerant is a bad idea because of the contamination, air, and the excessive head pressures.
David Teitelbaum

Chris4099
06-13-2011, 01:35 PM
Back to what I originally wanted to point out, the replacement for R-134a probably won't be $5 per can as it's even more expensive to produce. I can only see refrigerants getting more expensive over time, so having a properly sealed AC system is only going to get more critical. Fortunately I put in the new barrier hoses a few years back and I haven't had to do a R-134a recharge since. At least converting from R-134a to HFO-1234yf (assuming that becomes the standard) is a lot easier then converting from R-12 to R-134a.

content22207
06-13-2011, 03:02 PM
Forget about politics -- I want to talk A/C:

Whenever I say anything about these stupid little cars, someone pipes up that his or her car doesn't meet whatever the criteria du jour happens to be, and thus invalidates everything I've said. In the spirit of turnabout is fair play:

I just completed a 150 round trip errand in the DeLorean, in the middle of broad summer daylight. My A/C pumped wonderfully cool air the entire trip. Nothing blew up or disintegrated. As stated, I have never had a high side adapter on #5939 (I am however on my second low side adapter -- the cheap one broke). In my case at least it is entirely possible to do all your A/C work via the low side alone.

Bill Robertson
#5939

stevedmc
06-13-2011, 03:03 PM
Forget about politics -- I want to talk A/C:

Whenever I say anything about these stupid little cars, someone pipes up that his or her car doesn't meet whatever the criteria du jour happens to be, and thus invalidates everything I've said. In the spirit of turnabout is fair play:

I just completed a 150 round trip errand in the DeLorean, in the middle of broad summer daylight. My A/C pumped wonderfully cool air the entire trip. Nothing blew up or disintegrated. As stated, I have never had a high side adapter on #5939 (I am however on my second low side adapter -- the cheap one broke). In my case at least it is entirely possible to do all your A/C work via the low side alone.

Bill Robertson
#5939

How did it break? Was it leaking or did it snap somehow?

content22207
06-13-2011, 03:07 PM
It was one of those cheap aluminum adapters that presses on the original schrader valve. The pin inside went off center and bent. I replaced it with a proper steel adapter that contains its own valve.

Bill Robertson
#5939

content22207
06-13-2011, 03:12 PM
I wish I had brought my thermometer with me. Air at the vents was ice cold, but by the time it reached my seats I bet it warmed up at least 20-30 degrees. I reached under my dash mat and the dashboard was almost painfully hot to touch. My metal door handles were almost too hot to open the door. The front fascia was even hotter. Lower latitude sun exposure is absolutely lethal for these little cars.

Hopefully all the Yankees rubbing their hands in anticipation of DCS'12 realize what they're in for....

I'm definitely bringing my car cover.

Bill Robertson
#5939

Farrar
06-13-2011, 03:45 PM
I wish I had brought my thermometer with me.

Just for fun, I kept an over thermometer in my car for a while. After sitting in the sun, the interior temperature could be anywhere between 140°F and 160°F, even when the exterior temperature was below 90°F.

Farrar

stevedmc
06-13-2011, 04:23 PM
Just for fun, I kept an over thermometer in my car for a while. After sitting in the sun, the interior temperature could be anywhere between 140°F and 160°F, even when the exterior temperature was below 90°F.

Farrar

Wow. You could cook a steak in there.

content22207
06-13-2011, 05:12 PM
I was glad I had A/C today, but certainly was at no risk of pneumonia. These little cars really need front and rear evaporators, like a minivan.

Bill Robertson
#5939

Farrar
06-13-2011, 05:14 PM
These little cars really need front and rear evaporators, like a minivan.

I'd settle for an evaporator which didn't require eight hours of labor just to get at it. :angry:

Farrar

DavidProehl
06-24-2011, 03:17 PM
Just to close the loop on my original question:

I brought my car in today to have the A/C charged since it was guessed that was problem, turned out the system was bone dry. Something must have happened over the winter to lose it all. Anyway, I've now done a r134A conversion, I'm charged up, and it blows cold. Measured at 44 degrees.

Thanks for help troubleshooting to verify it wasn't other parts!

stevedmc
06-24-2011, 09:58 PM
That is awesome news. Did he try to find the leak or at least put some leak sealer in the system? You can get 3 oz cans at Walmart for about $5.

content22207
06-24-2011, 10:17 PM
If the leak isn't too bad (on the order of 1-2 cans per summer), it sometimes is better to leave vintage A/C systems alone and simply top them off rather than risk damaging thin wall components trying to separate them for O ring replacement (can I hear an "Amen" Farrar?).

I am uber fastidious about flushing my system to ensure that the evaporator pipe from hell (the one with the orifice tube in it) never needs to be messed with. I flush backwards to push any contaminants away from the orifice tube. My system has been opened several times to replace compressors, drop the radiator, replace schrader valves, etc. Every time I blow a gallon of paint thinner through it to ensure everything stays as clean as possible.

Bill Robertson
#5939

Farrar
06-25-2011, 03:13 AM
can I hear an "Amen" Farrar?

I'll go all Battlestar Galactica on you and add "So say we all." ;)

Although in my case I am not fortunate enough to have had the option: my car being an early VIN, it lacked a high-pressure switch or relief valve, so when my radiator fans failed to come on one day due to a bad diode the system pressure skyrocketed and I ended up with a hole in the high-pressure hose big enough to stick your thumb through.

I also have no air compressor, so flushing on a regular basis is not an option for me. I intend to seal the system well once the new evaporator and hose are put on, and then call it quits for that particular bit of automotive nastiness.

Off-topic tangent, woo! Er, I mean -- sorry. :\

Farrar

content22207
06-25-2011, 07:55 AM
I also have no air compressor....

Buy the little 3 gallon compressor Sears sells. The direct drive pump on it is the exact same pump they put on their 20 gallon unit -- the only thing you're sacrificing is stored air capacity (you won't be able to operate a paint gun or a die grinder). Basically you'll be living off the pump itself, which is fine for filling tires, operating an impact gun, blowing things off, etc. And of course flushing out an A/C system (or anything else you choose to blow air through, such as an obstreperous brake caliper). Sears had them on sale for $99 last weekend, and Friday/Saturday had an extra $10 off.

Bill Robertson
#5939

stevedmc
06-25-2011, 09:00 AM
Buy the little 3 gallon compressor Sears sells. The direct drive pump on it is the exact same pump they put on their 20 gallon unit -- the only thing you're sacrificing is stored air capacity (you won't be able to operate a paint gun or a die grinder). Basically you'll be living off the pump itself, which is fine for filling tires, operating an impact gun, blowing things off, etc. And of course flushing out an A/C system (or anything else you choose to blow air through, such as an obstreperous brake caliper). Sears had them on sale for $99 last weekend, and Friday/Saturday had an extra $10 off.

Bill Robertson
#5939

What about their pancake compressor? Is it any good? I noticed they had it for sale for $70 last weekend and a similar one was at harbor freight for $60.

DavidProehl
06-25-2011, 09:46 AM
That is awesome news. Did he try to find the leak or at least put some leak sealer in the system? You can get 3 oz cans at Walmart for about $5.

No leak sealer that I'm aware of, but there is dye in the fluid we can watch for should it leak out again. Looked like the leak was likely due to crumbling seals. Hopefully that was the case.

kings1527
01-14-2013, 12:17 AM
No leak sealer that I'm aware of, but there is dye in the fluid we can watch for should it leak out again. Looked like the leak was likely due to crumbling seals. Hopefully that was the case.

Hi Dave,

What all was replaced when you did the R134a conversion? Did you ever come across any other problems with your system/conversion? Did you ever find a leak in the system?

Thanks!

DavidProehl
01-14-2013, 09:39 AM
Sorry for not following up earlier on this thread. I think I may have had a couple threads going related to my A/C issues. I found the ultimate cause of my A/C problems to be a leaking evaporator. I couldn't find the dye that was put into my system anywhere, until I checked my evaporator drain. I replaced my a/c accumulator, evaporator, seals, and orifice tube along with the stanard 134a hardware at the compressor. I left my a/c hoses original. It has now been operational for a year and working great.