jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby lorge1989 » Mon Jan 11, 2021 7:47 am

The floors and carpet came out great! Never a fun job.
1988 Audi 90Q 1.8T 20v megasquirt'd and Holset'd
1994 Audi 90Q ABZ
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1978 GMC High Sierra

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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby jbrentd » Mon Jan 11, 2021 8:47 am

PRY4SNO wrote:That's well and truly one of the worst jobs on the car. Now that it's done things will get easier.

Or at least, that's what I keep telling myself haha


Let's hope so, but I still have to merge this harness with the 3B harness.

On that note, I see a lot of people have routed their 3B harness through the hole for the AC lines due to how the 3B harness is built. I intend to keep AC and am considering cutting a new hole in the firewall somewhere on the passenger side (with a firewall grommet). I'd rather do this then have a bunch of wires that are either too long or too short. Plus, the driver's side area under the dash doesn't need any more wiring than it already has. Any thoughts on that?
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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby jbrentd » Mon Jan 11, 2021 8:48 am

lorge1989 wrote:The floors and carpet came out great! Never a fun job.


Thanks! Just one of those Easter eggs I had to deal with.
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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby jbrentd » Thu Jan 14, 2021 12:16 am

I think I’m mostly done with stripping down the 7A harness.

Image

I do have a question about this T7 connector. I think it’s for the coolant thermoswitch. I did not remove it yet. Am I supposed to keep it?

Image


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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby varia » Thu Jan 14, 2021 11:50 am

So called "Aux" harness. Oil pressure, coolant temp, etc
¯\_(ツ)_/¯

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Re: jbrentd's 2nd Chance CQ - 3B Swap/Susp Overhaul In Progr

Postby jbrentd » Thu Jan 14, 2021 12:24 pm

varia wrote:So called "Aux" harness. Oil pressure, coolant temp, etc


Thanks Chris
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sun Jan 17, 2021 11:21 pm

So, that aux sub harness feeds several signals to the Autocheck system, right? If so, it seems I won’t need them on the 7A harness since the 3B harness has those same connections and I have the spreadsheet (BostonCQ’s) that shows where to tie those in to the 7A Autocheck.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Tue Jan 19, 2021 6:36 pm

Swimming in wiring diagrams and harnesses, but I think I have a handle on everything needed to run the engine. Things that are still left to figure out 100% are as follows.

1) carbon canister/evap. I don’t see where the 3B controls the second valve (shut off) like the 7A has.

2) AC wiring. I think I have this one figured out, but not sure if the manual HVAC swap is going to throw a wrench in things.

3) 3 stage cooling fan. I think I just need to dust off the wiring plans I’ve found over the years and figure out how to use the OEM UrS resistor pack I have.

Image


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Thu Jan 21, 2021 8:23 am

I think I’m ready to start soldering. I was in the garage last night mocking up the two harnesses. What’s left of the 7A harness is on the left and will go through the original firewall hole. On the right, is the 3B harness that will go through a new 2.5” hole in the firewall near the AC lines. I’m going to try and tuck the ECU in the same spot as the 7A ECU, but there’s a lot more lead between the firewall grommet and the ECU plug. So, we’ll see.

Based on my time spent with the wiring diagrams, most (but not all) of the splicing occurs between the wires circled in red. Exceptions are for the AC, after run, and 500w fan circuits.

It’s hard to tell if I’m going to have too much wire or not enough wire for each of the connections to be made. In most cases, I think it’s the former. I suppose I could do the soldering in the car, but that doesn’t sound comfortable. Any tips on this or the rest of my plan would be appreciated.

I made this document while reading the wiring diagrams to use as a guide for the merge effort. Please let me know if you see any issues with it. Hopefully it will be useful to others.

https://drive.google.com/file/d/1kBweR2 ... sp=sharing" onclick="window.open(this.href);return false;

Image

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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Fri Jan 29, 2021 5:45 pm

Splicing on the wiring harness is almost done. I decided to invest in a ratcheting open barrel crimper and have been pleased with it so far.

I have a manual HVAC swap question for to folks.

There’s a wire from the 7A MFTS to the climate control head that tells the system it’s okay to run the compressor. It prevents the AC compressor from coming on in an overheat scenario. Does anyone know where that wire goes for the manual HVAC?

This signal also goes to the 3B ECU, pin 36. I’m thinking it needs to go to the AC clutch relay, but not sure which terminal. If anyone has a wiring diagram for a B4 cabriolet manual HVAC, I should be able to figure it out.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sat Jan 30, 2021 6:43 pm

Worked on the battery relocation today. Just mocking it up in the engine bay because I will need to do some painting. I plan on running an Odyssey PC925 with the following:

  • Negative 2/0 to gas tank bolt
  • Negative 2/0 from passenger front frame rail (procon-10 bolt location) to transmission
  • Positive 2/0 from battery to 200 amp breaker
  • Positive 2/0 from breaker to battery terminal at firewall
    * Positive stock cable from firewall terminal to starter
    * Positive stock cable (from 7A harness) from firewall terminal to fuse panel
    * Positive from firewall terminal to headlight relays
    * Positive from firewall terminal to 70 amp high speed fan relay

Image

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Last edited by jbrentd on Mon Feb 01, 2021 2:45 pm, edited 1 time in total.
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby FFF » Sat Jan 30, 2021 11:42 pm

Looking good, I like the routing on the power cable, nice and tidy.
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby FFF » Sat Jan 30, 2021 11:46 pm

Not sure if you can find it locally but the POR 15 degreaser and a scotch pad works amazing for cleaning up the grease - by far the best degreaser I have ever used. I put it in a spray bottle, spray it on, let it sit, quick scrub and then wipe (I sprayed water on to remove any residue after as well)...
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sun Jan 31, 2021 9:14 am

FFF wrote:Not sure if you can find it locally but the POR 15 degreaser and a scotch pad works amazing for cleaning up the grease - by far the best degreaser I have ever used. I put it in a spray bottle, spray it on, let it sit, quick scrub and then wipe (I sprayed water on to remove any residue after as well)...

Thanks. Yeah I have a decent amount of that stuff left over from the 2 POR15 kits I bought and was planning to do just that with it. I agree, it is really good stuff.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sun Jan 31, 2021 9:52 pm

jbrentd wrote:Splicing on the wiring harness is almost done. I decided to invest in a ratcheting open barrel crimper and have been pleased with it so far.

I have a manual HVAC swap question for to folks.

There’s a wire from the 7A MFTS to the climate control head that tells the system it’s okay to run the compressor. It prevents the AC compressor from coming on in an overheat scenario. Does anyone know where that wire goes for the manual HVAC?

This signal also goes to the 3B ECU, pin 36. I’m thinking it needs to go to the AC clutch relay, but not sure which terminal. If anyone has a wiring diagram for a B4 cabriolet manual HVAC, I should be able to figure it out.


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To follow up on this...

I did some testing on the MFTS and the 2/R terminal (the one that goes to the AC clutch relay) is a normally open circuit. In other words, it doesn’t send the signal until the temp is high. Although not ideal, I’ll probably roll without that signal. That’ll mean my AC won’t shutoff automatically in an overheat scenario.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sat Feb 06, 2021 6:14 pm

Battery now lives in the trunk. Not sure why, but the idea of relocating the battery used to stress me out. I would over think cable size, relay location, etc.

Image

Image


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby FFF » Sat Feb 06, 2021 8:44 pm

Looks good - nice and tidy.
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sat Feb 06, 2021 11:18 pm

FFF wrote:Looks good - nice and tidy.

Thanks. Hopefully the engine bay will be the same.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby PRY4SNO » Sun Feb 07, 2021 2:20 am

Looks very orderly.

Does that say 770 CCA??
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jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby Afterthought » Sun Feb 07, 2021 8:31 am

Battery relocation looks nice and professional .
You did a better job than I did of removing the spot welds on the tray!

When I did this to my 90 I got some pre-mixed paint with the proper paint code for pearl . It comes in 3 aerosol cans (3 stages ) base , pearl effect, then clear . But here comes the slippery slope , it’s not a perfect match due to years of heat , you almost have to paint that area and then at least dust the rest of the engine bay
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sun Feb 07, 2021 12:13 pm

PRY4SNO wrote:Looks very orderly.

Does that say 770 CCA??


Thanks. That would be amazing from this little battery. It’s 330 CCA.

Afterthought wrote:Battery relocation looks nice and professional .
You did a better job than I did of removing the spot welds on the tray!

When I did this to my 90 I got some pre-mixed paint with the proper paint code for pearl . It comes in 3 aerosol cans (3 stages ) base , pearl effect, then clear . But here comes the slippery slope , it’s not a perfect match due to years of heat , you almost have to paint that area and then at least dust the rest of the engine bay


Thanks. There is one spot weld where I went all the way through, so I need to fill it with my welder. I need to learn some welding basics, like what settings to use for a small job like that. I don’t want to blow through it and make the hole bigger.

As for the paint, I was going to just do some touch ups, but I’m planning on a color change somewhere down the road. Not sure what the color will be though. I want to do it just this once. So, I’m trying to strip my bay and cowel area down as much as I can to prep it and paint it black. Just another bit of scope creep!


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby Afterthought » Sun Feb 07, 2021 4:52 pm

I have limited experience on body stuff , if it’s me doing it I’d wanna get the back side clean, use a mig, not tig welder l, and do it in very short bursts .
I can’t remember if it’s the inside of the rain tray area or inside of the cabin behind that but If you can get to the back you could get it clean then use a backer if possible .
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby PRY4SNO » Sun Feb 07, 2021 8:54 pm

Agree with Pat, MIG is handy for that. If you have the option of a spray arc or pulse mode use that too. Definitely stitch together a lot of tack welds and go around in a pattern gradually until sealed to minimize heat input/distortion. As always, prep is key.
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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sun Feb 07, 2021 9:25 pm

Thanks. I’ll give it a shot. Should be able to get enough access to the back to do it right. Will post the results here.


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Re: jbrentd's 2nd Chance CQ - Merging the 7A & 3B Harnesses

Postby jbrentd » Sat Feb 27, 2021 5:43 pm

Dealing with more BS not related to the swap...rust on the door sills this time. I forgot to take pics before I started. The before pictures are from 2014, so it had gotten worse since then.

Image

Image


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