A/C related

[kmckmc]

This problem happened about 4 days ago.

It was raining outside, so I decided to turn on the a/c unit after I had started the engine for about 20seconds.

As soon as I turned on the a/c unit, I saw the engine RPM increase abruptly to more than 2000rpm. And then I saw the BATTERY indicator light lit up (I suppose this means that the battery level is low). Previously, after I started the engine the battery usually shows about 13Volt; this time, it showed below 12volts. At that time, I quickly turned off the a/c unit. I also smelt rubber burnt smell.

I quickly drove the car to my mechanic. The BATTER indicator light went off just before I arrive to the autoshop.

The mechanic lifted the bonnet and pointed to me that A/C belt area has burnt smell. I suppose the compressor clutch was not working earlier. The mechanic told me to come back again the following day.

Next day, I have the mechanic checked the compressor. He told me the compressor still works; he used alternative power source to check.

He then checked the high/low pressure pipe and receiver/dryer for leakage. He could not find any leakage inside the engine bay. He suspeccted FREON has leaked. He then pumped in something/air?? to a conection which is close to the receiver/dryer, and found out that the leakage is not inside the engine bay; the leakage should be on the other side, ie UNDER the DASH.

My Elan's air con was working well 4 days ago!

What had gone wrong? The evaporator unit?

Please advise.

[TheBard]

Okay, I'm no expert here, but here are my gut instincts...

As soon as I turned on the a/c unit, I saw the engine RPM increase abruptly to more than 2000rpm. And then I saw the BATTERY indicator light lit up (I suppose this means that the battery level is low). Previously, after I started the engine the battery usually shows about 13Volt; this time, it showed below 12volts. At that time, I quickly turned off the a/c unit. I also smelt rubber burnt smell.

#1. If the car is cold/just started, and you turn the A/C on then the RPM going up and hovering around the 2000 mark sound pretty normal. When the A/C is activated your tickover increases.

#2. The voltage showing 13 normally, and dropping to 12 implies two things to me. My car normally shows just about 14v in normal usage, dropping to 13v-ish with the A/C on and running. Therefore, I would guess the drop is normal, but the low reading to start with is the issue. I would guess your battery, wiring, or alternator may not be working 100%.

#3. The battery warning light coming on is probably related to #2 above, and I'd guess that there is a battery/short/alternator charge issue.

#4. Burnt rubber smell could be your description of the musty smell the A/C can make if it hasn't been used for a few days, or might be a short somewhere burning the insulation off a wire. A short would lead to battery issues, see #2 and #3 above.

#5. The mechanic said that the A/C worked fine when another power source was used, so we can guess the A/C is not the major problem.

So, all told, I reckon you've got a wiring fault somewhere, probably a short leading to the drop in voltage, and as it appeared when you used the A/C I'd check the A/C wiring first. With the voltage you normally read appearing low, you may want to check the battery and alternator too.

As I said at the start, I'm no mechanic, and all this is just a guess, but I hope it gives you somewhere to start from.

Cheers,
Ian[/list]