Is this low refridgerant? and A/C Fan question... - PeachParts Mercedes-Benz Forum

ps2cho · #1 07-02-2010, 07:51 PM

This is for my 88 300TE. It has r134a in her.

Static pressures: 88psi

2000rpm: 15psi low 160psi high.

I haven't been getting hardly any decent cooling at all in the last year (haven't been driving her much though), so wanted check it out finally...Think it needs a can of 134a in her? What is normal r134a pressures on the w124 system?

Also, the aux fan does not turn on low when the A/C is engaged. Is this normal or should it turn on immediately? The aux fan does work though as I can remove the connector from the blue 2 prong temp sensor and it kicks on HIGH speed. Just bridged the connectors that plug into the aux fan sensor on the drier and the fans turned on. Safe to say it is that sensor that is dead?

Thanks,

lsmalley · #2 07-03-2010, 02:32 AM

my 190 had the same problem.....all it needed was to be evacuated and recharged. by the way, do you have a picture gallery of the car you have on your signature display?

Cal Learner · #3 07-03-2010, 07:38 AM

Quote:

Originally Posted by ps2cho

...Also, the aux fan does not turn on low when the A/C is engaged. Is this normal or should it turn on immediately? The aux fan does work though as I can remove the connector from the blue 2 prong temp sensor and it kicks on HIGH speed. Just bridged the connectors that plug into the aux fan sensor on the drier and the fans turned on. Safe to say it is that sensor that is dead?

No, I think it's a much better bet that it's low refrigerant charge than faulty pressure switch. Your other A/C symptoms are consistent with low charge. You know that the fan works, as do the relays, fuses and the serial resistor that steps fan speed down. A proper charge could very likely fix both your cooling and fan problems. You said "fans." Have you re-fitted your '88 with dual aux fans?

ps2cho · #4 07-03-2010, 08:09 AM

Quote:

Originally Posted by lsmalley

my 190 had the same problem.....all it needed was to be evacuated and recharged. by the way, do you have a picture gallery of the car you have on your signature display?

Well the A/C functions, just not very well, so I don't want to waste good refrigerant if it is just low. Is there a 'lifespan' per-say for r134a?

I have a few others I'll upload. I will have more/better ones soon though.

Quote:

Originally Posted by Cal Learner

No, I think it's a much better bet that it's low refrigerant charge than faulty pressure switch. Your other A/C symptoms are consistent with low charge. You know that the fan works, as do the relays, fuses and the serial resistor that steps fan speed down. A proper charge could very likely fix both your cooling and fan problems. You said "fans." Have you re-fitted your '88 with dual aux fans?

Typo. Single aux fan. I haven't touched the A/C in over 4 years since I bought the car, so as we all know the evaporators leak on these things, it could be leaking a tad every now and again over the years.

When should I stop recharging? 35psi low? What would be 'overcharged'?

david s poole · #5 07-03-2010, 11:05 AM

if your evap was leaking you would have no refrig in your system.an r12 system that has been converted to 134 will leak refrig out through the walls of the flexible hoses.for the conversion to have been done 100% the hoses should have been changed to barrier hose.your system is just low and 134 is a wuss when a little low on charge.bring those pressures up to about 35 on the low side and about 250 on the high side and you should be good to go.

lsmalley · #6 07-03-2010, 02:13 PM

as I have mentioned I experienced a similar problem in my 190, aux fans worked when I disconnected the sensor and the ac did work a little, I could heat the compressor engage and feel the engine rumble when I turned the ac on, but it just wasn't cold enough. I say evac and recharge because someone had also mentioned something about air pockets that could be causing you problems as well. In my case I only had 3 ounces of refrigerant in my system when the guy checked it for me. he didn't find any leaks either as he explained to me that he injected a dye in the system. its worth a try, no other way to tell if there is something else wrong unless you know for a fact that the system is fully charged with no air pockets

Hit Man X · #7 07-03-2010, 02:18 PM

Quote:

Originally Posted by lsmalley

as I have mentioned I experienced a similar problem in my 190, aux fans worked when I disconnected the sensor and the ac did work a little, I could heat the compressor engage and feel the engine rumble when I turned the ac on, but it just wasn't cold enough. I say evac and recharge because someone had also mentioned something about air pockets that could be causing you problems as well. In my case I only had 3 ounces of refrigerant in my system when the guy checked it for me. he didn't find any leaks either as he explained to me that he injected a dye in the system. its worth a try, no other way to tell if there is something else wrong unless you know for a fact that the system is fully charged with no air pockets

Uh, just look at his pressures... it is obviously low.

I do not even know what to say about air pockets in the AC system, I have never heard of it or seen it. I am not all knowning, but I have rebuilt enough to know that just cannot seem to exist.

David Poole is right on the money, you are not.

lsmalley · #8 07-03-2010, 02:31 PM

Well yeah, thats what I was saying that it could be low, as that was the case with my ac.......but "someone" had mentioned to me about air pockets in the system. I'm no automotive expert, but 99% of the time if I have an issue I turn to the forum and see what the consensus says....I don't just throw out things without not ever hearing about it as being a possibllity. Bottom line is air pockets or not, I think its safe to say that the most likely issue arises from the refigerant, or lack of refrigerant, and that to have it fully charged would rule out any other problems with his a/c.

ps2cho · #9 07-03-2010, 06:46 PM

I put in 2 cans of r134a...Took em mighty fast.

New pressures at 2000rpm:
27psi low / 240psi high
Ambient temp 76F, vent temp 61F

Think it could do with a 3rd can?

lsmalley · #10 07-03-2010, 07:31 PM

how much is two cans? maybe do half and then recheck.

#11 07-04-2010, 09:45 PM

No, you don't need a third can. You were undercharged before and probably slightly overcharged now. Your high side should be about 2.2 to 2.5 times ambient that would mean from about 170 to 190, but that would be with engine at a very fast idle and a fan in front of the car, so your pressures are not alarmingly too high.

Check your vacuum pods to make sure that you're not inadvertently getting outside air. Remove the glove box liner and check the lines on the manifold below the glove box. If there are any leaking, post which one or consult an FSM to see which is leaking. If it is the recirc pod, then there lies your problem.

ps2cho · #12 07-05-2010, 11:06 PM

Thanks Larry. Why is my high side so far above the low? I've read with my low side at 30psi, my high side should about 170 like you said...so why am I getting 240? Could it indicate a small blockage somewhere or something?

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