I am interested in this too, as I also have a 97hse.
Sorry to hijack, but it is somewhat related:
The other day I was under the bonnet and noticed some smoke coming from my ac compressor pulley area. I shut it off, and later turned it back on to try to duplicate but to no avail. When I spin the clutch, it has a little bit of intermittent crunchy noise. Is this normal or do you think it is bearings or the clutch going bad?
As most early P38A owners will know, the air con clutch would occasionally not engage and eventually it slips and wears to the point where it rarely engages.
An early fix was to remove a shim behind the clutch but this only deferred the problem.
LR came up with a mod. kit, the aircon Compressor Link Harness mentioned above, to increase the applied voltage to the compressor clutch.
I removed the shim in mine about 7 years ago, and fitted the link harness about 3-4 years ago, and this cured the problem - I thought.
However, last week the compressor clutch failed to engage once more. The clutch had worn even more and the air gap was too great.
Following a suggestion from Scouse, I pulled the clutch off, put it in the lathe, and machined off 25 thou from the back of the clutch spigot. That reduced the air gap back to within spec (0.35-0.65mm) and all is well once more.
When I pulled the clutch off, I found it had been wearing unevenly so I'll keep an eye out for another one (secondhand from a failed compressor). Note the wear at the lower left:
This and the other thread is brilliant. So i have issues with mine, a 1995 owned from new VIN no 355000 ish but when i look my fuse box has the air con relay and the air con fuse but no sign of the resistor or wiring harness. As far as I can remember (not far these days) i've not replaced the fuse box. So i guess best thing is to just check the voltage at the clutch connector with all the other electrics turned on and see if i get the 11.5 volts under load. Certainly the clutch engages and disengages adn cool air comes out from different vents so i'm assuming the blenders work.
What i do notice is the system doesn't seem to corectly asses the ambient temp so i'm going to check that.
Not sure if folks are actually retro-fitting this full harness kit to resolve all this but if you look at what they are doing with their 'harness' it is really just using it to operate a (spare) relay in the fusebox plus 'spoof' the (older) HEVAC ECU (- via the aforementioned current-sensing -) into thinking there is a happily-working clutch present.
However you could do all this easily enough yourself of course by using the HEVAC clutch supply to operate a basic (additional) 12V relay (alongside the same type of power resistor for 'spoofing' purposes), and then use that relay to supply 'full' (fused) 12V directly to the clutch instead (?) Result ? The HEVAC's happy and so is the clutch.... and if you mount this relay close(ish) to the clutch you don't need all those long 'harness' wires either....
It doesn't seem to have been a full recall on the ac clutch harness, unless I have read it wrong. I guess that means those who kept taking their RR to LR and/or had AC issues, will likely have had the harness fitted. Probably those who didn't have issues, still have the older wiring, and later on, some 2nd/3rd owner has trouble, but doesn't go to LR to work it out. You maybe then end up with something like mine which has the later (post 98) wiring harness, but someone has fitted the wrong HEVAC unit. Then we all end up chasing our tails! Paul, As far as not sensing the ambient temp properly, I think there were two locations for the sensors (which also corresponds to different HEVAC units), but maybe the ambient temp sensor is just playing up?
From when I read the TSB, it looked like it was initially a warranty fix... Not what I would call a "recall" but the TSB says something about "if a customer is complaining about the A/C then follow this procedure"
So that to me reads like LR knew it was an issue, but would do the upgrade in the harness if it was mentioned to them.. Rather than actively contacting people to get it fixed, fix the issue if the get a complaint from the owner about it..
Typically reactive rather than proactive!
**Edit: YMQ104590AA is the part number for the clutch link harness if it hasn't been posted yet...
- and this harness is a 'snip' at almost £100; Guess it gets fitted after the shim TSB has first been tried (or the nth. customer has had a new clutch); Don't know how many folks actually have this harness but one easy way to spot it is a relay in slot 10 in the box.. anyone else with an older rig have this mod. ?
Strange that the recall notice only mentions V8 derivatives up to XA411503. What was it about the diesels that made them impervious to the same issues and therefore not part of the same recall, I wonder?
my '96 had this issue and a previous owner records tried to unsucessfully resolve it with new relays. had i not come across this very specific technical bulletin and been able to find that part number it would probably still be a mystery. was able to source both the A/C Clutch Link Harness (YMQ104590AA) and the Alternator Link (YSB106340) and install them in about 3hrs. slow novice work and it 100% was the issue. A/C is now blowing cold on command. thank you.
Early cars drove the AC compressor clutch directly from the HEVAC via the pressure switch but it was found that resistance in the various connectors meant that the clutch was often only receiving 9 or 10 volts. On later cars the HEVAC drives a relay that switches the power so this problem doesn't occur. If your connections are good you don't really need the harness. Usual high resistance connection is in the multiway connector behind the RH kick panel and also sometimes the connector on the pressure switch. You cannot simply put in a relay as the HEVAC checks the amount of current being drawn by the clutch so if it is only supplying a small current to energise a relay it will assume the clutch is faulty and not try to engage it. Hence the official loom having a big resistor to increase the amount of current being drawn. Later cars had a HEVAC that didn't check the current and an additional relay in the fusebox.
The alternator link is simply an additional heavy duty cable that is fitted between the alternator and the battery to supplement the original that goes via the starter motor.