I guessed getting under there wasnt straightforward! Ebers are good!! you could easily tee it into the ducting if your fitting it underneath I guess too!
hes not wrong. My gaffer solution was a temp fix on a daily driver - all sorted now but still needs a little adjustment.
The system is straightforward, a fan blows air through ducting which flows over the heat exchangers and comes out of vents inside the vehicle. Simples! What could possibly go wrong? The system is great when new, and gives plenty of heat, but over 30 years later various problems will have appeared. The hot air has a long journey under the vehicle, and will prefer escaping through gaps to coming out of the cab vents. Starting from within the engine compartment, make sure the two uninsulated hoses are intact and blowing a maximum amount of air over the heat exchangers. Cheap hoses will rip, so replace as necessary. The H/Es are the hottest part of the system and also where the biggest heat losses can occur. The outer skins often don't fit very well, allowing air to leak. I first gummed up all the gaps with exhaust paste then wound heat resistant silicone bandage around the ends of the exchangers to further protect the exhaust paste repairs. Then I totally covered the H/Es with heat resistant bandage. It's the sort of stuff race car enthusiasts use to cover exhausts to give a better heat gradient. But for our purposes it's ideal to both stop leaks AND insulate the exchangers. Moving forward from the exchangers, check that the flaps open fully. On mine, the mechs were jammed so I made sure they were jammed in the "open" position. The next part of the system involves heavily insulated flexible hose. This can tear or rip so ensure it's all as it should be. It's available, but pricey, if any sections need replacing. On any junction of the insulated hosing, ensure there are no leaks and repair as necessary. But on mine all was OK. On campers starting as the minibus option, there's a "Y" splitter allowing some air into the rear of the vehicle. I disabled this by putting a rag into the hose, we want all the hot air up front! Where the hosing goes under the cover plate near the front of the vehicle, I installed a "marine engine room fan" to assist. It's design is such that it doesn't restrict the flow when switched off. But with hindsight I wouldn't have bothered, as even at idle speeds the engine fan is plenty powerful to provide a good flow of hot air. It's always possible that airborn debris has found it's way into the system and partially blocked it. As you're under the vehicle, it's possible to check for this by running the engine and checking for airflow (by feel) at various stages of the system. Safety first of course! Because my system has broken flap mechs, the heat is on all the time. To cope with this in the summer, I've covered the lower vents into the cab. When no heat is required, simply direct the heat downwards and the system is effectively cut off. For parts needed, just do an eBay or Google search on "exhaust bandage", "silicone heat bandage", "marine engine room fan". The system has been up and running for 18 months now, and works superbly, a credit to how VW meant it to be! Lashings of warm air on the coldest of winter drives, wish I'd fixed it years ago. The first priority is to repair ALL air leaks, secondly to insulate the weak point of the system, the heat exchangers. As the summer draws to a close, NOW is the best time to address the perenial problem of cold campers
