a/c out again :(

[glowstang93]

About a month ago I replaced the low pressure switch and it worked fine untill today. I replaced the switch again, but now the compressor clicks to start and then clicks again, but doesn't really start it up. I'm thinking the clutch may be out, but need some opinons. The clutch was replaced about 6 years ago so it is electromechanical one, not the old stock rubber bushing type. Any ideas where to start or how to check to see if clutch is bad?

Appreciate the help in advance. Thanks

 

[HISSIN50]

Anthony, I'd try and ensure you have a good electrical connection at the LPCS and that 12 volts is reaching the clutch itself.
If you jump the switch, does the clutch engage?
You can even use a fused jumper to check the clutch's ability to lock-up (this removes bad wiring and the WOT relay from the equation).


And if you have gauges, I'd put them on to start with (I didnt think you did though). Seeing static pressures and knowing ambient temps can give a slight clue about overall system volume.

Random thoughts.
Good luck bud.

 

[glowstang93]

I jumped the low pressure connector and I can get the compressor clutch to engage and stay engaged, but the air is still hot out of the vents. So, with that said, it sounds like my clutch is working.

Now I am thinking that the low pressure switch is doing its job and keeping the compressor from kicking on due to low freon pressure.

Next step?

By the way thanks for the ideas.

 

[HISSIN50]

At that point, I'd get gauges on it. You could kinda use a low side gauge only, but the issue is that they can be off (I've seen them be off by 5 PSI, which is huge on a low side reading). One of those gauges might give you a decent idea. Otherwise, Harbor Freight or parts stores sell R134 gauges that work well enough for guys who use them on a car or two a year.

If the pressure is actually ok with the LPCS jumped, don't forget to chase wiring in case there's an issue. A lack of juice can make the clutch chatter.

Good luck bud.

 

[glowstang93]

Ok.....So , if I jump the low pres switch, and then put a voltmeter on the compressor 2 wire plug ...what should it read? Also do I check across the two wires or from one of the wires and the other meter wire on ground?

If its low on pressure, sounds like it will be going to the shop I use for probably a new accumulator, and convert to 134a.

Just can't justify buying gauges when I won't use them very often.

Thanks JT

 

[HISSIN50]

I hear ya on the gauges Anthony. If you ever have the cash and if you have other older cars, the gauges can be had for about 40 bucks on sale (I think HF even had theirs for 30 on sale. I've used their older version before and they were accurate enough).

You should see battery voltage across the clutch connector (one meter lead on each wire). This tests the circuit using the same pathways the clutch has available.
If you check the clutch's ground, look for less than 5 ohms of resistance (continuity to ground).

If you're just a bit low, I'd consider just topping the system off with R12. As long as you dont have some big leak, you should be money ahead going that route anyhow. I really don't convert unless I have to (just MHO there).

Good luck bud.

 

[glowstang93]

You should see battery voltage across the clutch connector (one meter lead on each wire). This tests the circuit using the same pathways the clutch has available.
If you check the clutch's ground, look for less than 5 ohms of resistance (continuity to ground).

I checked the voltage across the clutch connector with the low pressure switch connected and got 0 volts. I checked the clutch connector with the low pressure switch connector jumped and got 14.0 volts.

Is it still looking like the problem it low pressure (ie low on freon)?

Could the accumulator being clogged cause low pressure?

 

[HISSIN50]

Anthony, without being able to make observations in person, it does sound like it is a lack of refrigerant. If you have a cheapo low pressure gauge that fits your ports, you could connect the gauge and then jump your LPCS again. Your low side pressure reading real low would indicate that the system is low.

To make determinations about clogs, you need to be able to compare the low and high sides of the system, and then factor in the ambient temperatures to see where you should be.


If you or your mechanic buddy don't mind, have him put dye in the system. You might find that you simply have a bad o-ring or a leaking valve.

Good luck bud.

 

[Fett]

Yea, sounds like you are low on r134. When it is low, your compressor will cycle on and off...if it is very low, it will cycle on once and then stay off. When you jump the switch, you are forcing the compressor to stay on.

You need to recharge and add dye, when it starts blowing cold again use a black light and yellow goggles to find the leak. Replace the leaking part and recharge, you should be good to go.

 

[glowstang93]

Well, my mechanic friend checked the a/c out today. He found the only leak to be at the low pressure sensor connection. He put on a new pressure switch, vacuumed out the system. Added Freeze 12 to the system since it is $8-10 a can vs changing to R-134 right now. I have no clue why I would have had a leak at the low pressure switch, but time will tell how the a/c holds up. He also added the dye so if it leaks out again, he will be able to find the problem easy.

If I had retrofitted to R-134, he said I would need a new accumulator which is $150-$200 depending on where you get it.

I know at 98 degrees its freaking hot in southeastern Illinois right now.