I have a 1985 XJ6 that is having a blower problem. The only fan speed I have is the low setting. It blows low on all the fan settings. The air moves out of the correct vents (defroster, dash, heater). The only thing that doesn't work is the high speed fan. I'm wondering if it could be a fuse or relay somewhere. Any thoughts? Thanks!

 

OK, fun is about to begin.

Under the LH console cheek, where your Right knee sits, is a 4 gang relay box thingy. This is the relay thingy for the fan speeds.

Being an '85 car it SHOULD be a 4 pack, as the early cars had a 3 pack, with the LOW speed being a seperate relay just forward of that pack. I think the 4 pack came in at "about" '82??.

Remove it, that is the fun bit, and seperate the cover, and clean the contacts inside.

MARK/LABEL ALL THOSE WIRES FIRST. Your memory aint that good, trust me.

In behind that relay, up in the innards of the beast, is a small ECU that among other things, controls which relay is switched to give what fan speed.

The relay pack is not a common failure, but age is against it now.

The ECU IS a common failure item. Plenty in the search areas on it. It also has an inline fuse in the black wire, and they do also fail at times.

 

Alright! I have seen the black relay four pack with all the wires. I'll try to open it up and clean the contacts. That ECU is something I'll look for. Hopefully the in-line fuse on a black wire will make it easy to spot. I'll keep you posted. Thanks Grant!!!

 

That ECU is behind that relay pack. You will have to remove that relay first.

Then you SHOULD see a whitish plastic round multi pin plug, and the section of that plugs wiring disappearing in towards the rear of the radio is heading for the ECU. That ECU is held in a DUMB spring clip that WILL NOT let it leave the hiding place. Your hands will be too big, and all sorts of language will be uttered, then for some reason totally unknown it "pops" out. Now these are apparently HARD to find. Some were available from down here a long time ago, and home made, and very good.

With all the models I have had using that ECU, I have never had one actually fail, Aussie luck I suppose, and the fuse blown has been the main issues I have encountered.

On the side of that ECU is a small access hole to insert a small screwdriver and adjust the even smaller "pot" inside to better put the fan speeds into range. This is "fine tuning" at its most primitive, and the smallest movements make HUGE variations, and it took me YEARS to get the hang of doing so.

I still reckon the fan relay will sort your issues. It has been MANY. MANY years since I have been into this area, BUT, I seem to remember an earth wire from that relay going under one of the relays actual mounting nuts, and if someone has been in there before, and omitted that wire, the relay will NOT work, and the default "slow speed" will be all you got, mmmmm. That wire is a major PAIN, and so are the mounting nuts, coz access is ZERO, as you maybe already know.

 

Yeah Grant, I have been in there before and know that there's not much room. Do you know the name or part number for that ECU? It might help me look for one if I get no results from cleaning the relay or cleaning and replacing the in-line fuse. Thanks, Walt

 

I don't know if my issue is related to this topic thread but my Jag has blower issues as well. It only blows hot air, no A/C, even when it's just supposed to be blowing ambient air. I imagine that the A/C pump is shot but looking for other ideas and guidance.
Thanks.

 

Walt,

The part No is C45402, and is no longer available. I would try the guys at XK Unlimited in San Loius Obispo. I use them at times for ODD stuff and they are good in my opinion. They may have an aftermarket unit??????, or even a s/h unit.

The official name is an "air conditioner amplifier".

 

NO, in a word.

Your hot air is more than likely as simple as a heater tap stuck ON, very common.

I would suggest starting a new post about it, that way teh answers will be related to your issues.

 

That would be great if it is! Thanks! Will do.

 

Well, I tried all of Grant's suggestions with no luck. I'm considering trying to find an AC amplifier, but I'm not sure what the symptoms of a bad one are. They are scarce and pricey and I'd hate to pay for one if it's not going to help me. Does anyone know what a bad one acts like? Thanks, Walt

 

HAHA, now you want to test my memory, HELL.

Ign ON (acc position will do).
RH knob on AUTO.
Rotate the LH dial slowly, and you "should" hear the innards of that ECU click, maybe hold it in your hand as a feeling may be easier with all the noise that will going on, and as it does so the servos on the RH side of the a/c unit "should" start whirring in accordance with the temp asked for. Also the fan relay pack SHOULD click as it changes fan speeds, as that ECU switches that relay.

Make real sure that your fan relay pack is a 4 relay unit. Most I have played with are 3, with the slow fan relay sitting right next to it. I think?? that the slow relay I mention is a 4 pin unit, and NOT standard pin numbered. The "30" pin is where standards have the "85", and so on.

I know the fan speeds are not going to change (that is the issue you are sorting), BUT, the servos should drive from end to end with temp alterations of the LH dial.

NOW, if the servos drive, the ECU is deemed OK as far as I am concerned.

Our Daimler 1976 S2 was a real mongrel when we first got it waaaaay back, and it took me a couple of years of sorting/testing/why does this do whatever, before I found the earth wire omitted from the front mounting stud of that relay pack, fitted that, and all sweet, but in the meantime I had dug into all the bits of that "lovely" system looking for answers.

Some of the little things I have come across over the years are:

2 very SMALL nuts in behind the RH knob (radio out for access if you are blessed), are loose by 1/6 turn, and simply tightening them restored fan operation.

The inline fuse in behind the RH metal air outlet (where the handbrake lever is on a RHD car) blown. That is a pain to get at on RHD , but it reeks havoc with the system.

The pad temp sensor waaaaay up the top on the LH side water pipe into the core is dud. I always join the 2 wires together.

That relay pack, we did discuss it previously.

The fuse in the ECU loom.

The resistors for the fan speeds, up in the LH air trunking. Not a common failure, but old age is at them now.

The infamous 50amp fuse in the main fuse block. I bypass that with 2 self setting circuit breakers (split the systems), and do away with that fuse. It melts the plastic, and CAN actually burn wires.

Cant think of anything else just now, but who knows later.

 

my zest for jag knowledge has me readin these posts daily. grant...that was impressive!

 

HA, thanks for that.

Before "arthritis" and the Right leg went west, I was into anything just to find out WHY. Since I have only EVER owned Jaguars I soon learnt HEAPS.

No one down here EVER wanted to work on a Jag, so I had to do it, or change cars, NAH. First wife did that, "the MK10 or me", still got the MK10, so I reckon I made the right choice????.

Drinking came top of the list about 1972, still up there according to the wife.

Hoarding started in 1968, and also still going on, and a bigger shed is on my wish list HAHAHAHAHA.

Add to that the cars were always the daily driver, so had to be mobile for school runs, shopping, whatever.

I have always maintained that "if I cant fix it, it aint broken", and still stubbornly maintain that today.

PAIN is now my best friend, along with the wife and the Jags in that order.

 

hahahaha...thats great man.

 

Thanks Grant! I'll try to test the ECU and see if I can get any results. I'll take a shot at running down those fuses too. If that doesn't work I REALLY like that drinking suggestion. Thanks, Walt

 

Walt,

Just had a zap in the brain.

IF you turn the RH dial to "defrost" you SHOULD get:
1) High fan
2) Max heat.

That position over rides ALL ECU,/thermostat etc settings.

If you dont get that, then the micro switches in behind the RH knob, then behind the radio panel are MOST LIKELY the issue. Access is a JOKE, but those 2 SMALL nuts I mentioned before will be loose, and simply tightening them nearly always returns the system to spec.

When you go to "defrost" the servos (on the RH side of the unit) will "drive" (whir) and the relay pack should switch to HI, so it is a very basic/simple test of the system, prior to going to all sorts of testing and tail chasing.

 

Okay! That's the way I'll go. As of right now switching the control to defrost has no effect on the fan speed. I'll try to get to those loose nuts on the fan selector switch. I'm still going to do some drinking though. Walt

 

So it has been ages but I was very curious if you ever solved your blower problem. Mine is doing the same thing. switching to defrost is blows hot but at a weak setting, not enough to clear the windshield that is for sure. still on low. and turn on the heat and the blower almost turns off

 

I had similar problems with my system, but had no fan speeds or occasional system function. Turned out to be the Mode Switch or the rhs switch. Replaced it and system works as it should. Pain to replace it so test all other components first.