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Hello All. Been a long time coming but open road seems to be gettting closer and closer. Got a little hung up with new bike and posrche 928 projects,,, but I'm ready to dig back into the XJS... Excited, actually
Question:
Im wondering if folks have figured out some sure fire ways to keep as much heat out of the cabin with an undercarpeting??? I have a new carpet set on the way, didn't break the bank, and I wanna keep it that way. Jute, tin foil, a special insulation? I'm all ears.
I trust everyone is doing well and once again,,, thank you all so much, in advance. The well of information here is,,, well - there ain't no words for it.
The photos are from a few days ago. Getting it out,,, thanks to the threads of info from folks here,,,, was kinda a no sweat thing. Left me all sore tho, lol. Not getting any younger..
Believe it or not I didn't have a 16mm wrench to take of the calipers. But,,, brake job, clean everything up - wire wheel and such, waxoil... New parking and main brakes. Speed bleeders, discs, diff oil, differential mounts on the way. Exhaust connections... I'll be needing a new passenger side muffler. The one in the middle of the car. I still have not figured out how the get the Speedo on the dash working BUT I finally found a "new" and reportedly working inDiff speedO sensor, finally... New PS Pump. New A.C. compressor... The list goes on.
I used Dynamat, works really well. I often drive with AC off and windows down in summer and before the Dynamat the feet used to swelter, now I can comfortably do that with out cooking my feet. The other thing you will need to do is turn off the heater tap when the AC switched off, the default is on allowing hot water through the heater core further heating the feet.
The other thing you will need to do is turn off the heater tap when the AC switched off, the default is on allowing hot water through the heater core further heating the feet...
Hi Warren... Been a while.
Ok! Heard. I'm going to start looking at dynoMat,,, and you in now me, the cheap skate, I'll have to look for a cheaper version. Not so cheap as I am limited in funds, but hey.
And, to close the heat tap is a simple as pulling the vac line off under the hood or, is it a matter of closing down the whole linein from the rad? How? I'd never considered this.
Pulling the vac line opens the tap you need to either add a solenoid valve inline to stop water flow or better still apply vacuum to the tap, this can be done by turning on the vacuum solenoid that applies vacuum to the tap, a switch that disconnects the AC ECU and applies 12v to the solenoid will work.
So, in the summer,,, warm weather or when I want,,, in principle, I should be able to just run a vac line from somewhere to the vac spout at the top of the valve and keep it in the OFF/CLOSED position? I don't really want to mess around (any more) with that damn HVAC climate control ecu than I have to...
I'll try and keep it simple,,, lol, I'm learning how that works out...
For some reason the A.C. compresor controls of the piano shaped HVAC ecu were the only thing with the heating system i couldnt figure out... It would never send enough power ti kick over and engage the compressor relay (only like 4 or 5 volts),,, so I wire up a switch. It's (at this point) the only toggle switch I have in my controls - for the A.C.. Glad for that.
So for now, I can get the a.c. on and when it's on everything else does what it should. In that, I guess the ecu tells the valve to close and ***** down the vac to to the valve. Is that right?
Can you post pictures or something I'm having a hard time following this, but my car now is like driving a coal fired train its absurd. I dont want to cut the supply line TO the heater core for a manual valve if I can help it.
If it matters my AC unit is leaku and belt removed anyway for now.
Can anyone confirm that the heater valve can completely close off all coolant flow? I have a spare from a xj6 that has notches in its plate. There is always some flow through it. I haven’t, yet, removed a heater valve from an XJS to look inside.
So pin 20 from the ECU only has 4-5volts on it, is that correct?
Piano shaped ECU that's the MK3 which only turns the heater tap off on full cold.
Hey Warren. From memory yes,,, something like 5 or 6 volts. Off the top O my head I don't remember the pin. I had started a thread about it a while back and I could never figure out why the voltage was so low AND,,, a new ecu was impossible to find or toooooo expensive. It wouldnt kick over the relay to engage the compressor. And yes, it also went into other areas of the HVAC system to turn off and turn on other functions, like heat...
So, not only didn't it kick on the compressor, the compressor relay not kicking in didn't supply power to that little extra breather on the PS (LHD car) air filter. To solve, I took 12 volts off that common white 12volt wire that connects to multiple accessories in the car, got a switch, and toggled the a.c. compressor relay. Worked like a charm for compressor and small breather. The little breather is a device that allows a little more air into the TBody to give an extra 50 or 80 rpms to compensate for compressor load. Sorry a lot of this is from memory,,, but I learned this all off of a wiring diagram. I remember black and purple wires,,, and lots of green and white wires. Also ran thru an idle control relay at the front of the engine bay if I remember correctly...
I have the A.C. working now,,, I could see my breath in the air stream, then the compressor (I had rebuilt it) wouldn't hold the r12. I am planning on a new compressor with that shorter straight up and down belt - soon. I've removed the aux blower pulley set up and wheel.
I think the valve will shut down the water flow to the heater core. I don't use her as a daily and (for me) won't be any problem at all to tie into the intake plenum to get vac somewhere during summer months... If that's the solution,,, even if manual,,, it's a wonderful solution for me. Grant it the one who gave me lessons on the valve if I remember correctly...
Warren,,, I'll be looking you up when it comes time for the cruise control No doubt
The Jaguar heater control valve is a vacuum-operated pot metal contraption located in the dead center of the firewall, under the rear loop of the fuel rail. It consists of a metal cylinder with a hole through it within a ported housing; the cylinder is rotated to align the hole with the ports to allow flow, and rotated so the ports face the blank sides of the cylinder for shutoff. This valve is expensive, difficult to get at, and prone to corrosion and seizing. Note that a heater valve should provide a total 100% shutoff of water when vacuum is applied; if it is leaking when closed, even slightly, it introduces quite a lot of heat into the climate control system when it is supposed to be in full cool mode. While the supply air from the vents may still seem cool thanks to the operation of the flaps bypassing the heater core, the system won't work as efficiently as it should.
On the 1983 XJ-S, the mount bracket is held to the firewall with two bolts that thread into nuts welded onto the firewall. However, Michael Bain reports that some models use nylon nuts within the wiper motor area. In this case, it may be easier to remove the intake grille/wiper motor assembly and unbolt the heater control valve from the back side.
Do not simply eliminate the valve and plug the hoses. The hot water supply is necessary for proper operation of the climate control system, even when it's in cooling mode. A temperature sensor in the heater core will limit the blower operation if the water isn't warm enough.
When the valve causes problems, you can take it to an auto parts shop or auto A/C shop and ask for a Chevy valve that has the same size hose connections. The Chevy valves are a butterfly type and are made of plastic and stainless steel, and weigh so little that they don't need to be mounted; they can merely be suspended in the hose. They also cost only about US$20. Make sure the valve you buy is normally open, and applying vacuum closes it. With a little hose rerouting, one of these valves can be located at the right rear corner of the engine compartment where it's easy to get at.
An even better option is to replace it with a Jaguar valve! The newer XJ's use a valve made entirely of plastic -- no metal at all -- and cost half what the Chevy valves cost. Although some people don't like plastic, the design of this valve is so superior that it is probably the most reliable choice; since it is a poppet valve rather than a rotating-cylinder valve like the Jaguar original or a butterfly like the Chevy valve, the reliability of a total shutoff when closed is much better than either. Reportedly, Pep Boys sells an aftermarket version of this valve made by Factory Air, part no. 74803.
Warren, sorry I could get the image as an image - just the link and I'm not even sure if it will work. This is the diagram I used for the a.c. work on my car back in 2018... So yes, the green and white (GN) from 20 and then there was another wire from the controls that was involved. I'll need to really study this to figure out that second. I'm terrible with these damn diagrams
The ECU has drive transistors inside I suspect one of these transistors has failed in your ECU, I had the one that drives the centre vent solenoid die in my ECU
The ECU has drive transistors inside I suspect one of these transistors has failed in your ECU, I had the one that drives the centre vent solenoid die in my ECU
What would it take to identify and repair somethimg like that,,, if it's even possible?
I'll dig out my spare ECU and see if I can identify which transistors control the AC compressor clutch. It is rather difficult as I don't have a circuit diagram and all the traces run inside the PCB but not impossible.
I have the same problem with the AC compressor not coming on with the fan switch. (It had been working fine but after doing myriad maintenance under bonnet it just quit working?) Following the wire schematics I realized the relay was not being energized when the fan switch was moved from off to any of the the speed settings. So I wired the relay with a powered toggle to energize it and subsequently engage the compressor clutch. Perhaps one of the transistors in the ECU failed like you stated above? One problem with this is that the extra air valve (to increase idle speed) doesn't get energized. Nor is the thermal switch on the fuel rail able to automatically turn on the compressor to cool the fuel returning to the tank. So ultimately I'd like to properly fix this. But for this summer at least I have working AC.
Ok I have identified the Transistor that drives the AC clutch relay. It is a ZTX550 and I am pointing to it here.
To test it use a DMM on Diode test and Red probe on pin nearest the PCB edge and black on the other 2 pins your meter should read about 0.6V also check centre pin and furthest from PCB edge Red it should also read 0.6V. More than likely this TX is bad.
Post back the readings so we can see if the TX is bad.
06-13-2019, 03:45 PM
Keeping heat out O the cabin. Carpet underlay
No doubt
