Suprazed

Hello all, I've just recently purchased a 2001 LS430 with 175,000 miles on the clock and although almost everything works I'm experiencing issues with the air con.

When I bought the car the a/c compressor clutch would not engage so the first thing I did was to get it re-gassed. I was told that about 150g was recovered from the system and it was then refilled with an additional 700g (total capacity is 900g), I was also advised that it appeared to be holding pressure as expected. However, this had no effect and the compressor clutch would still not engage.

Here's what I've done so far
(with help from the a/c troubleshooting guide here;
http://askatech.com/AskATechLive/for...er.ashx?a=7773 );
1. Run the diagnostics and recovered codes 23 and 28
(Pressure switch and rear solar sensor)

2. Tested the pressure switch voltage (as per the guide) which read about 3v (well within normal range) so I guess there is still sufficient gas in there. (Or is that not necessarily the case)?

3. Removed the connector on top of the compressor (the one with 3 wires) and supplied 12v direct from the battery to the pin where the black/white wire would go (this is for the magnetic clutch).
At this point the clutch engaged and the compressor began to spin. I left it running for a few minutes but cooling didn't feel as cool as it should. Switched on rear a/c (I also have the fridge) and it was much cooler and as I would expect.

4. I then did another test which was to bridge the 2 points where pins 3 and 5 of the compressor relay would go and this also engaged the compressor successfully.


So my question is, what do I do next??


TIA

Tom57

Have you checked all of the A/C fuses including in the under the hood fuse boxes? By supplying 12 v. directly from the battery, you are confirming that the compressor engages, but also by-passing all of the fuses. Check fuses first.

Also, since you are getting the pressure switch code, I'd replace that switch. Problem is, you have no way to recover the full re-charge of freon gas, so you would lose some freon if you DIY replace the switch. (There is a CL thread on this; the switch is right up front on right side of radiator.) The pressure switch is tested by checking voltage based upon pressure. It is a safety switch that turns on compressor only when it detects sufficient minimum freon gas pressure in the system. Since you re-charged the system, you know there is adequate freon pressure. However, 3 v. may not be enough as your attached guide states 4.8 v. for full pressure in system.

Suprazed

Hi Tom, you say 'all the fuses,' how many are there?

I think I only spotted one which was 7.5 amps and it looked fine (actually, I may be thinking about a fuse inside the passenger foot well, I don't remember).

I think the only fuse box I checked under the hood is the one that also contains the compressor relay.

Are there other fuse boxes under the hood which I should check?

Thanks

Tom57

Check Owner's Manual which will show fuse purposes and locations.

Suprazed

Ahaa, in the UK it seems that the MG CLT relay is marked as a/c compressor, no wonder I couldn't find it.

So this is the relay which I already tested, I also swapped it out with a relay nearby (headlights) but no luck.

When i bridged the locations where pins 3 and 5 go, the compressor started running, I just don't understand what is preventing it from running using the controls inside the car.

The other point that's baffling me is why after I bridge the relay I get cold air in the rear but ambient air in the front.

There must be something obvious I need to check

Suprazed

Thanks rkw,
I'll check the fuses, I already checked one which is in the driver side (uk) kick panel and that was definitely ok. I don't recall swing one marked as IG A/C under the hood though so will check again when I get home.

As for the steps in the attachment you sent, the only checks that I haven't done yet are to check the solenoid and the clutch resistance (the 2nd and 4th items in the attachment) the other 2 checks came up fine.

I'll post an update later.

On a more positive note in the meantime, I repaired the ML subwoofer using Aleenes tacky glue, seems ok, although it has now revealed that the door speakers may also require attention! !

Thanks for all the advice so far.

Suprazed

Ok, followed the advice in rkw's post including the pdf and all checked out fine. As far as fuses concerned I swapped out with others that I know are good but compressor still not kicking in.

BradTank

If none of the fuses come back as the culprit, my instinct says to double check on the amount of R134. I think it's still low.

I know you said the shop recharged it, but the fact it was about 80% empty tells me you have a leak somewhere and they never found it. It could have leaked right back out or the shop made a mistake while they recharged it?

That amount of leakage on a car this age means there's an issue beyond just the normal seepage that can sometimes occur with age. That should have been found by the shop that charged it.

Lavrishevo

iTrader: (1)

From what I understand, you can also look at the little glass "window" at the high AC side right in front of the condenser. Just below the horns. If you notice bubbles circling in that window, with car hot and running you are low on R134 and fill until you no longer see any air bubbles circulating. This is what I did on my 400 and it worked well. I believe I filled on the low side. I want to say a Lexus tech told me about this.