AC stopped working mid-drive

[DeanG]

AC was working great 300 miles into a 1700 mile trip to LOG it just stopped producing cold air. What can I check in a motel parking lot? I'm off to check the fuses and see if it cycles when flipping the on switch.

[Ian T]

All you can really check is:

Is the drive belt still fitted?
Is the compressor clutch spinning, or just the pulley?

I guess you could check the fuses also.

I don't know whether the Elan has any control positions where the AC is disallowed, some, for example won't run the AC if the cabin fan is switched off, some cut the AC while under hard acceleration.

Hope this helps.

[DeanG]

Fuse looked OK, but swapped it with the known good one for the cigarette lighter which was powering the GPS. The clutch does not seem to work. Cycling the swithch changes the engine RPM and turns the AC light on but the clutch
doesn't seem to engage. Off to dinner and to cool off. I'll check back in an hour or two.

[Brit-Car-Nut]

Fuse looked OK, but swapped it with the known good one for the cigarette lighter which was powering the GPS. The clutch does not seem to work. Cycling the switch changes the engine RPM and turns the AC light on but the clutch doesn't seem to engage. Off to dinner and to cool off. I'll check back in an hour or two.

Cycling the switch should turn on the idiot light but the engine RPM shouldn't change unless the clutch engages as it is the drag of the compressor that causes the rpm change. The idiot light is part of the AC switch and is before the AC relay.

The power to the AC clutch is protected by the Trinary switch which is threaded into the Receiver/Drier in the engine bay. It closes only if the pressure of the freon is above a low limit and open if the pressure goes too high. If you have a leak, the pressure might have dropped below the minimum to trip the switch or the switch has failed. It is a common US type switch so if that is the cause, you should be able to source one.

Check for power at the PINK wire going to the Trinary switch. IF there is power, then the Trinary switch is possibly bad, the ground has been lost or the clutch coil has failed.

You can call me on 704 395-29 four nine if you need something posted to you.

Here is the wiring diagram: Click on it to actually read it...

M100-AC-Diagram-small.jpg

Download a larger version here: http://www.lotusm100.com/LEC/M100-AC-Diagram.jpg

[Simon_P]

The switch increasing the engine rpm is good - That means that the ecu is getting the a/c command.

There are really then only 2 things to test

Low o r high gas pressure - signal controlled by the trianary switch on top of the receiver drier.

Evaporator temperature - signal controlled by the switch on on the the end of the evaporator - This switch often fails. The simple test is to remove both leads and connect them together with your paperclip or a piece of wire.

[Simon_P]

The a/c select commands an increase in idle speed independently. So you will get an increase in Rpm even if the clutch doesn't engage but not if the evaporator temperature switch is faulty.

[DeanG]

OK, some things to try. Thanks. I will post updates as ASAP.

[Brit-Car-Nut]

The Trinary switch is also pretty fragile, so as long as your freon hasn't leaked away, you could bypass the Trinary switch temporally. I can send one to your hotel in Colorado if you find that is the problem.

I hope your trip improves and you have a great time at LOG.

[DeanG]

When we get to CO I will have it looked into. It has been bearable with the windows down.

So far I have seen a murdered out tour buss, lots of little kids in cowboy boots, Lear jet as yard art. In for the nitht at Abiline KS. I had a decent steak and am watching the KC Royals beat the Angles.

[DeanG]

The car is currently in Courtsey Automotive. It appears there is a freon leak at a hose fitting.

Ross lent us his yellow M100 while ours is being worked on.

[Brit-Car-Nut]

That certainly accounts for it not turning on the clutch. If you need anything, parts wise, let me know. The lines are all basically standard, so your shop should be able to make or get made some replacements.

[DeanG]

The local shop finished the work today. It was the temperature switch.

Car has been washed and is in the LOG parking lot. 1887 miles driven from home to LOG.

[Ian T]

Excellent, sounds like a mercifully inexpensive repair as well.

[tedtaylor]

Coincidentally, my A/C gave up the ghost on the way home from LOG37 in Birmingham this past week. It was working perfectly fine the whole trip down and back (although only "cool", not real "cold") but my failure was more severe in that a sudden "SCREECH" sound of the fan belt. I immediately shut off the A/C switch and the noise stopped. I knew immediately that the A/C compressor seized up, thus the serpentine belt running friction across the stuck pulley. Thankfully the belt didn't break and i was able to make it home the rest of the way. Once home, i double checked the situation and turned the A/C switch on momentarily and sure enough.... "SCREECH". So i confirmed the A/C compressor locked up.
Now the question remains, until i actually remove the belt and/or compressor for a "hands-on" inspection, as to whether the compressor seized or is it possibly the A/C pulley clutch mechanism?
Does anyone here have similar experience that could share?
I've had the car 6 years and it's running original R12 and has been operationally fine, although i have noticed a slight reduction in coldness lately - then again it was really hot (mid-90's and humid).
What is the exact replacement compressor make and part number?
any suggestions/help much appreciated.
thanks
TED

[DeanG]

I have been avoiding turning on my AC since LOG36. It died on the way home. I'm just starting to dig myself out of the hole I'm in. Hope to get to it within the next few weeks. Good luck.