Idle Boost Diaphragm - AC system - where to find and do I have/need one?

[atariguy]

I have an 88 Aerodeck, auto with the A20A3 engine. The only thing about this car I don't like is that she doesn't have A/C.

I got the opportunity to pull the major A/C assemblies from an 88 LXi auto. Don't worry Greta, the fluids were long since removed.

Looking at the digital service manual on page 23-2, I got everything except the Idle Boost Solenoid Valve and the Idle Boost Diaphragm.

In a forum post back in 2016 @Dr_Snooz stated:

Not sure about the '86s, but the LX-i's don't have an AC boost
solenoid. It was integrated into the IACV.

So I am hoping I don't need that part since these are the same engines. But what about the diaphragm? Do I need that? Do I have it? And can someone please possibly post a hi-res picture of what the thing looks like so I know what I am looking for.

Would really appreciate some help!

[ShiRen]

I have a vacuum delete on my a20a1 and I just have to set a high idle and it works out ok with the ac on. You don't need it, if it doesn't function properly because you are putting ac on a non ac fuel injected car and the iacv doesn't compensate, you will just have to do the same and raise the idle. The fuel injection will compensate for load at least. I'm pretty sure the idle boost solenoid is a carb part, so it won't work for you anyway. I think all trim levels share a body harness, because I sure do have a lot of extra connectors, so if you do indeed have all the parts it should be plug and play and your ecu will know to turn the iacv up.

[atariguy]

Thanks @ShiRen - that makes sense.

So I was hoping I had all the parts I need for this project, but now the next issue. Where does the AC wiring loom plug in? The loom I pulled had a round 7-pin connector which matches what the manual seems to show in the diagram.



I cannot find this connector in the Aerodeck's engine bay. The car has the connector for the evaporator under the passenger side carpet, and it has the wiring connector for the A/C on/off button so I think the car was designed to allow for AC as a dealer upgrade. The best I could find was a small unused 4-pin square connector right below the retractrable head light on the driver's side. Am I right to guess I need to strip the wiring loom back to the fuse box by unbundling the wiring looms?

I've also noticed that Honda had a wiring harness A and a wiring harness B (P/N 38711-SE0-000). B looks to be a subset of A but perhaps I am wrong on this?

Appreciate the help, hoping someone know the deal on the wiring!

[ShiRen]

I can't think of where that is off the top of my head, but I know which one it is because it is massive. I'm pretty sure it is below the left headlight or above the wheel arch in the fender. I will dig through the manual to see if I can find anything, but luckily for you my bumpers are off and I need to remove my fenders to gap panels, I can check after work today.

Edit: I believe you are holding C-41, which is an 8pin-1 in your case, connects to C-86 in the main harness. It would normally be behind the headlight, but C-86 might be tucked back into the fender. I will take a pic on my car when I can. It connects to the main harness going back in the left side of the car so I don't think the fuse box has anything to do with it.

[atariguy]

That would be freakin awesome! Yeah if you can help me find this - even if I have to take the fender or bumper off to get at it - it would mean I finally have all the parts I need for this project!

Thanks in advance.

[ShiRen]

Here is where I tucked it, you can get to it through the fender liner.


Here is where it usually sits, by the right headlight motor. Sorry for the exposure lol, but I am pointing at the hole it goes through, your car probably has a plastic cover here.

[atariguy]

@ShiRen - if you're ever in Seattle I owe you a drink!

With your guidance I found the connector. Exactly where you said it would be. I was able to remove the grommet in the picture, and using an Xacto knife, reach in and cut the blue tape, and tease the connector back into the engine bay. The connector was covered with a black plastic cap.



Removing the cap shows the connector.



Thank you again for all your help!

[ShiRen]

No problem m8. Tbh I forgot about all the stuff a normal car has in the way of that hole lol. Hopefully this gets working without much need of an idle booster, I'd like to know.

[atariguy]

No problem m8. Tbh I forgot about all the stuff a normal car has in the way of that hole lol. Hopefully this gets working without much need of an idle booster, I'd like to know.

So the A/C is installed and working. You were absolutely right - no need for an idle boost with fuel injected engine.

A big shout-out/thank you also to Jeremie Peterson of Bellingham Auto Air who did the final install and system charge, and also figured out a few last minute issues. Of course the weather is turning cold and crappy now in Seattle, so it will be Spring before I can really get the full benefit of this, but very happy to have working A/C.

[ShiRen]

Sweet!