nileseh Posted June 14, 2022 Share Posted June 14, 2022 I think I'm having a bit of an intermittent problem with the air doors on the AC system on this car. The shop manual doesn't have much related to the electrical and vacuum system. Does anyone know of a source for electrical and vacuum schematics for this system. I'm not sure what other Defenders use this system, it's all built in with vents across the facia but I've not seen it in other Defender versions. Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 14, 2022 Share Posted June 14, 2022 That sounds like the system used on pre-Defender 90s and 110s in the 80s, with the black fixed panels where the bulkhead vent flaps would normally be. If so, it should be in the earlier manuals. Quote Link to comment Share on other sites More sharing options...
nileseh Posted June 15, 2022 Author Share Posted June 15, 2022 Oh. I had no idea. That's exactly right. The vents are black panels (the very panels I'm think I'm going to have to reseal to correct a pesky water leak). So the manual I'm looking for is not a Defender, but a Series III 110 or 90? I thought all the series trucks were called 109 or 88. I don't suppose you know where I can get such a manual? Quote Link to comment Share on other sites More sharing options...
western Posted June 15, 2022 Share Posted June 15, 2022 Early vehicles you need the 1987 on 110 parts book https://www.brooklandsbooks.co.uk/product/land-rover-defender-90-110-130-parts-catalogue-1987-2006-my/ Try Brooklands book they sell via Amazon. Or from retroanaconda.com http://www.retroanaconda.com/landrover/2010/02/land-rover-defender-110-parts-book/ Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 15, 2022 Share Posted June 15, 2022 You need the One-Ten manual. It was what the Defender was developed from, but the Defender name was applied when the Tdi engine was introduced and a few other changes were made like smooth roofs and the doors with the plastic push-button handles instead of the the recessed levers. Land Rover retrospectively applied the Defender name to the entire heritage of the utility model, including SI-SIII, and the 90/110/127 take a bit of knowledge to spot from the actual Defenders that came immediately after and share most parts, so confusion is to be expected. Quote Link to comment Share on other sites More sharing options...
nileseh Posted June 16, 2022 Author Share Posted June 16, 2022 Making headway and learning lots. The British car industry seems to be plagued by uncertainty in naming. I've encountered the same thing with Jaguar XJ6 series cars and XJ40 cars labeled XJ6. It's difficult to keep straight. The parts manuals are great, but the workshop manual is still problematic. I found a electrical schematic, not as simple as I imagined, but the vacuum remains elusive. From the parts descriptions there are numerous vacuum valves associated with the controls and vacuum "motors" (I assume to be diaphragm servo operators) but it's not clear what air doors are operated by these things and with what logic. The hot water valve for the heater is also tied in with a vacuum operated valve. I found a Haynes manual (not a fan) that purports to be for 83 all the way to 07 so I'll see if that sheds any light. Any other suggestions will be appreciated. Thanks all. Quote Link to comment Share on other sites More sharing options...
simonr Posted June 16, 2022 Share Posted June 16, 2022 My Td5 Defender 110 had two vacuum solenoid valves on the right inner wheel arch. They were connected to the wiring loom & to the brake vacuum, but with the outlet (inlet) capped. I never figured out what they were for - but I wonder, now, if they were for Air Conditioning, if it was fitted. Si Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 17, 2022 Share Posted June 17, 2022 23 hours ago, simonr said: My Td5 Defender 110 had two vacuum solenoid valves on the right inner wheel arch. They were connected to the wiring loom & to the brake vacuum, but with the outlet (inlet) capped. I never figured out what they were for - but I wonder, now, if they were for Air Conditioning, if it was fitted. Si EGR valve removed? Quote Link to comment Share on other sites More sharing options...
simonr Posted June 17, 2022 Share Posted June 17, 2022 45 minutes ago, Snagger said: EGR valve removed? EGR was still fitted. The valves had sealing caps on the vacuum outlets & looked like they'd never been attached to anything? Quote Link to comment Share on other sites More sharing options...
Troll Hunter Posted June 18, 2022 Share Posted June 18, 2022 My 1991 CSW (LHS) had two vacuum operated doors in the heater/AC system, one in the air intake inside the right wing and the other operated a door within the ducting behind (in front of) the dash panel. There was a third vacuum motor that operated an on/off valve in the heater water system. All these are covered in the LR 1987 110 Parts Catalogue. If you need any replacements be prepared to sell at least a kidney! Mike 1 Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 10, 2022 Author Share Posted July 10, 2022 Well, I appreciate all the comments, and have learned a bit about the system. I also spent some time moving levers with and without vacuum to see what moves under what conditions. I've ruled out vacuum being the problem. My experience is that on a long drive the volume of air decreases and the temperature of that air increases from the facia vents. I thought perhaps I was losing vacuum that operator a door that directed blower air (post evaporator) to the facial plenum. Not the case, I think now the total air volume to the interior is decreasing. Pretty much a clear case of frost buildup on the evaporator restricting air flow and insulating what does get thru from the evaporator heat exchange. Of course the evaporator is totally enclosed so it is not possible to observe the condition. There is a note in the Owners Manual that the evaporator can freeze over in maximum cold control position, and the remedy is to bump the control up a bit. I'm not sure what that is intended to accomplish. In any case it doesn't work. The lever operates push-pull to a door in the evaporator box that I think mixes air with the heater core. It also operates a vacuum valve that opens the coolant line the the core. But it does not, as is common in AC systems, change the setting on the thermostat that senses the air temperature at the evaporator. The control thermostat is apparently fixed so it does not open the circuit to the compressor when the temperature goes below an operator selected point. So if this thermostat is faulty, the compressor could be on continuous rather cycling as is the case with most AC systems. And of course the part, RTC7434 is nla. That said, the thermostat is on the outside of the evaporator enclosure and the temperature probe tube goes thru the top adjacent to the evaporator. Should be an easy conversion to an adjustable mechanical replacement, or even conversion to a thermocouple solid state temperature control (I did this on another car sometime ago and it works well). If the replacement is adjustable I should be able to empirically determine an appropriate control temperature. But I don't suppose anyone knows something about this system, for instance what temperature does the thermostat want to see to drop the compressor out? Then of course I appreciate comments on this diagnosis: am I dreaming or does this make sense? Niles Quote Link to comment Share on other sites More sharing options...
simonr Posted July 11, 2022 Share Posted July 11, 2022 Your diagnosis sounds very likely. It also sounds an easy thing to test. It may just be that the electrical contacts have burned / corroded and you'll be able to hear it click at the correct temperature. It may even be rebuildable. Most electrical parts from that era can be dismantled & cleaned. Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 13, 2022 Author Share Posted July 13, 2022 A bit more to update..... Evaporator temperature ranges are published in the workshop manual. I checked this by inserting a meat thermometer in the hole intended for the thermostat switch and found that the evaporator core is well within specification for the conditions, 95F outside temp and I measured 52F at the core. However the air outlets in the car were at 75F. That didn't seem right. I little bit more investigation led me to the air mix door controlled by the temperature slider on the facia. As it happens, the full cold position did not fully close the door on the heater core side. The core does not contain hot water by virtue of the vacuum water switch, but a bypass for ambient air is provided to mix with the cold air from the 52F evaporator core. 95F ambient will warm air up quite nicely. I adjusted the cable to firmly close the door on the heater core (the notion is that the foam that originally sealed the door was gone leaving a gap). Instantly I have 65Fto 68F air from the vents. So a 25-30F drop from ambient which I am told is normal. The other issue of reduced air is probably what I suspected a bit ago: freeze over of the evaporator. The temperature switch that seems to be intended to prevent this remains closed (compressor engaged) at 28F, I couldn't get any lower, but at that temperature the core will freeze and humidity in the air. I'm calling the switch defective after 30 years in service. The switch is, as noted above, nla, but I found a adjustable capillary operated switch, with 6mm male spade terminals, intended as a refrigerator control for $9.00. I'll set that for 36F or so insofar as the workshop manual shows the minimum temperature expected of the evaporator core under ideal conditions is 40F. That should drop the compressor out well before freezing. I think that does it. I'm going to call the effort successful. I love it when that happens. Niles Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 13, 2022 Author Share Posted July 13, 2022 Also, with reference to simonr above, once i get the original switch out I'll try to repair it. However my hopes are not high. The contacts could be welded, or the diaphragm operated trip mechanism could be jammed. I can probably fix both of those conditions. But if the gas in the tube has leaked out it's over. The refrigerator switch is a safety as required. Quote Link to comment Share on other sites More sharing options...
montyjn Posted July 15, 2022 Share Posted July 15, 2022 Glad you got your issue sorted. I had a similar system rebuilt a few years back. Details and some pics (including of the inside of the evaporator etc) here: https://www.facebook.com/page/110025449507749/search/?q=land rover Quote Link to comment Share on other sites More sharing options...
montyjn Posted July 15, 2022 Share Posted July 15, 2022 Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 16, 2022 Author Share Posted July 16, 2022 Thanks. But I'm in the US and the AC system in the NAS trucks is quite different. Of course it mounted on the right, and the configuration of the evaporator, heater core, blower, plenum is not simply opposite hand, it is completely different. The documentation for these systems is lacking so I'm going to draw up the airflow path so I don't forget. However I think the control is about the same RHD to LHD. Nor sure though. I hope to rebulid the system at some point, but that project sounds like one for a clean, warm garage on a cold winter day. Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 17, 2022 Author Share Posted July 17, 2022 The story goes on.... I removed the original compressor thermostat control, RTC7434, in anticipation of replacement with the refrigerator thermostat. Also to see if it was serviceable. As it happens it is not a fixed device, it is fully adjustable, with separate adjustment screws for setting the core temperature at which the contacts open and close. Go figure. The adjusting screws are on the back of the device, facing the Evaporator housing and not visible without removing it. Also not documented in the workshop manual. It probably was repurposed from a refrigerator or freezer application after all. I carefully drilled a second hole in the top of the evaporator housing so I can place a thermometer parallel with the thermostat probe, ran the AC and set the open point to about 32F and the close point at about 50F. I think perhaps after 30 years the expansion gas in the system has slightly decreased shifting the mechanical set point down a bit, but it is still within the adjustable range. I'm going to leave the thermostat hanging for a while to fine tune the set points before I remount it. Another observation: I think the operation and set point on this component is pretty important to correct operation of the system. I bypassed the thermostatic switch while removed, ran the engine at idle, 70F ambient and low blower speed. Under those conditions the core rapidly went to below 20F, sufficient to freeze any moisture pretty quickly. That is of course ideal conditions to freeze, increased air flow, higher ambient will mitigate low core temperature, but after it freezes the system won't operate until it defrosts. It seems it would be worth while to check operation occasionally to be sure it is cycling the compressor. Quote Link to comment Share on other sites More sharing options...
simonr Posted July 18, 2022 Share Posted July 18, 2022 That sounds like good news! Quote Link to comment Share on other sites More sharing options...
nileseh Posted July 31, 2022 Author Share Posted July 31, 2022 A final closeout on this..... I received the mini-refrigerator thermostat, inserted the probe into the core and connected the compressor control wiring. By golly, it works nearly the same as the OEM Land Rover part (that is nla) when set to the lowest temperature. So I have a replacement if the original item goes out. I spent a bit more time adjusting the original engage-disengage core temperatures. System is working brilliantly. We have had a week of unusually high temperatures here in Eugene, 100F plus a bit, and I'm seeing full air flow at a 25-30 degree drop from ambient. Once the initial cooling takes place in fresh air mode, I change to recirc. It makes for a quite comfortable cabin in this big old truck. Successful conclusion. 2 Quote Link to comment Share on other sites More sharing options...
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