Hi all

I have the following issues in heating dept. with my 1977 XJ-S:

First issue:
Heating is not working. A/C is working, maybe a little weak. Heater valve is ok, and corresponding coolant hoses get warm, so there must be flow, but there's no heating in the cabin.
I found a 8-pin connector in LH footwell, which I believe is for the servo unit. Somewhere I found that the servo motor should be connected to the red and purdle wire. I do not measure any connection bwtween those wires, so maybe it's 'just' the motor, that has given up ?

Second issue:
Fans do not run at LO, and at AUTO, HI and DEF they run at full speed. Both fans do this.
I was suspecting the resistor pack RTC677 as both fans were failing and was planning to remove it for inspection, but after finding it placed pretty deep into the dash I decided to measure resistance in situ: There are connection (with different resistances) between all combinations of connectors, so it must be OK.





I found this old thread arguing that it's most likely darlington transistors in motor regulation, that is defective, but do I have type of electronics this in my old XJ-S ?
JEC BB Index

I'm well aware that the preHe is becoming a rare beast and that most knowledge on this (and other) forums is on HE models.
Do you have any suggestions where the preHE brain trust is found ??

 

Delanair 2 is used 1974ish to about 1987ish.

S2, S3, XJ-S.

1) Those servos rarely die. The amp unit, tucked stupidly in the depths of the dash via the LH console cheek is a known problem item. It has an inline fuse in the Black wire, and that may be blown??.

2) Fan speed issues can be anything, BUT, the multi relay unit that sits in your face under that LH console cheek is a suspect. SOME of the early cars had a seperate relay mounted just forward of that relay pack and it is for the LO fan speed ONLY. It has an ODD pin layout, so watch the wiring carefully when replacing it.

3) Remove the radio, heater knobs, 2 nuts behind those knobs, and radio escutcheon, be bloody careful with the fibre optic strands here, look at the Mode switch mounting area, the RH one, and note the 2 SMALL setscrews that hold all that unit together. They come loose, its an age thing. Reach thru the radio opening, and if your fingers are small enough, you will "feel" the TINY nuts. Hold them whilst tightening the 2 setscrews. This has fixed many for me over the years.

4) Look carefully at the FRONT mounting stud of that relay pack I mentioned in #2, it is also an EARTH stud, with lots of Black wires attached. These wires break, get left off when stupid plays in there, and things fail to work. NOT a real common issue, but I have found a few with wires not attached.

After that the fun starts.

That amp unit is the "brains" of the system, and there are better/newer units available via Google or ?bay. Check with the Parts Suppliers that support this Forum, ya might just find one.

 

Here is a document about the Delanaire II that may also help.
The troublesome amp is part no C45402. Second hand ones are available and sometimes new digital ones which are much better.
Greg

 

Thanks a lot, Greg and Grant.

I actually thought the early XJ-S was using a Delanaire I (or something else different from HE-models), so this is good news, and I now have a good handfull of things to find, check and test.
I just might do a photo of my LH footwell with covers removed and ask you to guide me. It's a bit like a snakepit to navigate in...

 

I found the multi relay, got it out as well and found 2 relays not working. The cause was broken thin wires as expected after reading up on the subject in Kirby's book, so these are now resoldered.
Now I just have to reassemble and cross my fingers that I have a full range of fan speeds.

Is the flat unit I see behind the multi relay the amplifier ?
Anything to do with it when I'm in there (except from replacing it) ?
I read there are updated/improved versions of the amplifier. What should I go for ?

 

Decisions, decisions.

The failure of that amp in the total picture is lo, but if I had mine apart that far, I would go for a newer digital unit, and FORGET about removing the old one. Simply fit the new one to the loom plug, and tuck the amp wherever it will fit in the snake pit. It will NOT complain, trust me.

Those hair wires you sorted are more than likely the root cause of the issues.

 

Thanks for a quick and clear answer

I will leave the amp in place, assemble and cross my fingers. If needed I will then afterwards change the amp to a digital version. Any hints on what to choose and where to buy ?

I expect fans to be working as they should now, but could the failing relays also be the cause of missing heating ? I can answer this myself after reassembly, but am a bit curious...

A few pics from the relay operation:

 

Those hair wires are probably the fix. I have done them over the years, and simply forgot to mention them earlier.

The newer amps apparently appear on ?bay from time to time. I have only ever needed one in all the years, and nicked it from a wrecker.

The lack of heat is probably a jammed shut heater tap, and/or a blocked heater core. That blocked core is more common than owners admit.

While you are under the dash, reach up above the steering column, and "feel" for the pad style temp switch on the heater inlet pipe. Remove the 2 wires, join them together, and that will ensure the system is "awake" as soon as the ignition is ON, instead of waiting for that pipe to get up to temperature. Failure of that switch is getting common now with age.

 

Fan is now running, but I don't think it's entirely by the book as I have low fan speed on OFF and LO and high fan speed on AUTO, HI and DEF.

Heat is still not working, but A/C surely is...
The piping to the heater matrix gets warm (in the footwell), so there is flow. The switch on the waterline has zero resistance when water is warm, I guess that is correct. I also tried to mount a manual switch, still no heat.

I have airflow in all vents, and changing temperature or fan setting does not change this.

Is it time to try a new amp ?

 

Yep.

Some of the OE amps have an adjustable "pot" on one side, but getting that old one out will really test your sense of humour.

Adjusting that "pot" very, very carefully can bring the system back into synch, sometimes not. My XJ-S responded well to very small "pot" adjustments over a few days, and worked very well once done. The amp was already out of its hole.

I have no idea if the digital amps have that"pot" as I have had zero to do with them, butcommon sense says yes.

 

My amp has the pot and it's fairly easy to access, so I will give it a small adjustment. The car is cold to drive now the fan is running all the time.
If a small adjustment doesn't work, it will get a larger twist...

 

Leo
Clockwise = hotter. If you get the car warmed up and have it ticking over with the amp access ready and the aircon on, by turning the screw clockwise you should hear the engine note change as the amplifier kicks out, and turning back clockwise hear it change again as the compressor kicks in.
Also, if you lie on your back and get a torch, having removed the shin level trim on the LHS, you can just see and touch the heater pipes, and thus verify if any hot water is getting to and from the heater core.
The digital amp does have a similar trim screw, by the way.
Greg

 

I can now report, that the heating works !

Or rather, it worked... I fiddled with the pot screw, no result at first. then 10-15 miles into a drive, heating started working and worked for the next 25 miles. Happy days.
After a 4-5 hour stop we drowe on, and was not happy to find the system being back in the usual non operative mode, but at least I know that it CAN work...
Further pot screw manipultion didn't help

 

Goodo.

I reckon you need some inenr nectar to warm your blood. Once nice and fuzzy, adjust that pot, it will all be sooooooo clear.

Good luck.

 

I think that pretty much proves it is the amp. Mine started doing that sort of thing when it went home.
Greg

 

Thanks !

I have looked for the digital replacement amp on eBay without success.
I suppose there must be someone producing them ? Contact informations, please
European supplier preferred to avoid customs and fees at import, but any source is better than none !

 

Also, SLOWLY work that "pot" end to end, NO force, just work it back and forth.

It just "might" settle the track and give a non-fuzzy signal.

I dont reckon it will do any harm.

 

I got mine from David Manners. I do not know if they have stock right now, I bought mine about a year ago.
David Manners Ltd - Jaguar Parts, Daimler parts, genuine Jaguar parts, OEM parts and reproduction parts from David Manners Ltd


Part number is C45402. Best to give them a ring and ask.
Greg

 

Thanks Greg and Grant

I will do some pot-motion. Until now I've only turned it maybe a quarter of a turn. How much is the turning angle ? Around 270° as a normal simple potentiometer ?
If this not helps David Manners is next stop
Next update will be sometime next week. I'm bloody busy doing home improvement, but responding here was a nice break...

 

Contacted David Manners yesterday by e-mail and got the message that they don't supply the Jaguar Climate Control Amplifier C45402.

I found one expired listing on eBay Australia: Jaguar Climate Control Amplifier C45402 | eBay
400 AUD (= 300 USD). Is this what I shall expect to pay for the uprated amp ?