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  #76  
Old September 16th, 2019, 23:07
xeroOTG's Avatar
xeroOTG xeroOTG is offline
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Location: North Bend, WA
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Re: John's 98 Build Thread

It is time for my wiring writeup. I’ve put a lot into the wiring on this Jeep. I’m only going to document the non-obvious parts. For the obvious parts, I used this diagram:



AC Control

The AC is the craziest, so I’ll start there. The AC Circuit is broken into three parts:
  1. AC Request Relay
  2. AC Clutch Control Relay
  3. Fan Request Relay

The Jeep controls ground a wire when AC is selected. This for our purposes is called AC_Request. AC_Request on the VW side is 12v+, so we need to flip that around. Next, we have the “Bidirectional Climate Control” circuit (94/50), which in VW goes to either a climatronic, Relay 378 on the B5’s or a Fan Control Module in the A4 types. This pin is pulled to an internal 1.8v supply when AC is allowed by the ECU. This is worthlessly low to us, so I used a couple off the shelf transistors, resistors, and a diode to convert to 12v to drive yet another relay to control the Compressor Clutch. We also need our cycling switches, so we hook those up to ground and to the other side of the clutch control relay.



To waterproof the transistors, I put them inside of a piece of heavy duty waterproof heatshrink.





The next piece of magic, I used a 2 speed Volvo fan and relay. It switches the fan on based on either the low or high wire being connected to ground. In order to do this but only when the jeep is on, we need yet another relay.



Fan Control

The two speed Volvo fan and relay are a good junkyard snag – the fans are very high flow and slim, and the relay is well matched to the draw of the massive fan. I mounted the fan relay between the battery and fender, so the wire can remain short. To switch the relay I snagged a thermal switch out of an A4 platform car, 1J0 959 481 A. It threads right into the jeep radiator. I de-pinned a connector (1J0 973 203) I got at the junkyard and connected it up.





1 - Low
2 - Ground
3 - High

Coolant Glowplugs

The coolant glowplugs in the A4 platform are switched by two relays. One is a 70A Bosch Mini, and the other is a standard 40A. The combined circuits are 50A, so this one is super straight forward. Throughout this, I reused my Jeep relay box, which for space reasons is primarily made up of micro relays with a max rating of 20A. Each coolant glowplug is rated at 17A, so we can easily use three relays instead of 2 and keep everything stock in my relay box!



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  #77  
Old September 16th, 2019, 23:33
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Re: John's 98 Build Thread

I threw a belt! As predicted by some, the belt walked into the timing cover and shredded all it was worth. Fortunately, I was sitting in the drivers seat and turned it off before any damage could occur. The fix is to use pullies with flanges. Easier said than done! I read somewhere that the recommended maximum bend radius for a pk6 belt is 90mm, so there just aren’t a lot of pullies to pick from if you need a smaller circle. I already went through this selection process once. I settled on an industrial pully from McMaster-Carr 6235K68 for the smooth side of the belt, and a Gates 38082 for the grooved side. The belt length remained constant but is significantly tighter. The McMaster-Carr pully is for industrial belt and has a 6203RS bearing like everything else so it should hold up just fine. I bought a couple so I can keep one in my glove box.



There have been requests for my turbo adapter design – here it is. Let me be clear, I had Matt Whitbread manufacture mine, I do not know what, if any, changes he made.

I was concerned that the exhaust was a tad close to the firewall, so I wrapped it. All in, wrapping a downpipe is pretty straight forward. I used a DEI basalt based wrap, finished it with stainless zip strips, and sealed it with a silicone exhaust temp. I like how it looks!





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Old September 16th, 2019, 23:59
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Re: John's 98 Build Thread

One other thing I’ve spent a lot of time on is the transfer case shifter. I really like the looks of the atlas twin stick cable shifter, so I got one. They are quite pricy, and unbeknownst to me use a non-standard cable length, so there was a lot of fab to make it work.



The simplest modification was the EcoBox bracket. I bought Jon Barlow’s bracket for this expecting everything to bolt up. I ended up shortening and flipping the bracket to work with the shorter throw cable of the atlas shifter.



The more complex one – the NP242 has a very long throw. The shortest of shift levers was still too long of a throw for my cable, so I had to fabricate up a bellcrank to lengthen everything. To make matters worse, the bracket I bought for this was from Dirtbound Offroad, and it was incompatible with the strengthened webbing of the EcoBox. I ended up needing to cut it in half to get its mounting ears into place.



I found a new turbo on ebay, the original was definitely failed. I could not find signs of wear, but the bearings don’t feel too hot. Once the new turbo was bolted up, I got a tune from Malone Tuning, and drove to the gas station to fill up. 30 gallons of diesel ain’t cheap!

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Old September 17th, 2019, 06:39
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John's 98 Build Thread

This build is sick. Nice work man. Take some video and post it up.
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