I thought I'd post in a new thread, not to hi-jack the last one.

I have a 1991 civic si hb and I've installed an A/C from a sedan 1991. everything went in great. did the o-rings, expansion valve, blew the lines out, dumped the oil out of the compressor and put 3oz of ester oil in the compressor.
The wiring harness a grabbed has 3 connections near the coolant fan. 1 to run the fan.(not plugged in) 1 is the A/C pressure switch(plugged in) (go to the A/C hose) and 1 is the CTS plug.(not plugged in)
I don't have the system charged up yet, so I jumped the A/C pressure switch. The clutch engaged and the A/C fan came on.
Using the original CTS plug and coolant fan plug, the coolant fan did not come on with the A/C fan.
When I plugged the new coolant fan plug into the fan, the fan did not come on when the temp in the car came up.

The location of my CTS is on the engine (1600cc) not on the Rad.
I read that when the ECU detects one fan coming on it starts the other fan. This is not the case for me.

Should I try plugging in the CTS plug and the coolant fan plug from the new A/C harness in? Will the ECU recognize the new plugs? What do I do with the old plug? Can I hard wire the fans together with a diode between them?
I'm at a loss here.
Has anyone done an install before?
Brent

 

I'm a bonehead. Deleted. Look at the next post. That is the correct information.

 

the ECU does control the fans with A/C - here is the wiring diagram:

 

Yup. I sure was wrong. I'll delete my other post. The diagrams speak for themselves.

 

thanks

It looks like diodes control the fans. Wonder where this item sits?
I tried to post a pic of the plugs, no can do.
the plug attached to the side if the distributor , same two colored wires as the CTS plug, It fits too, but the car doesn't start when I plug it in

 

I don't think that is the right spot. But I was wrong before.

 

since my car never had A/C maybe I don't have a A/C diode pack.
Any one knows what it looks like and where is it. I can't find it anywhere, on the car or on the internet.
thanks
BM

 

on the cars with A/C, the diodes are located on the passenger side, behind the dash, below the carpet - they are on the A/C wiring harness - wire colors are yellow/green and (2) blue/red

 

thanks
I'll go look.

 

yup, part of the A/C wiring harness I put in. And it's still there. I was sort of hoping the diode wasn't there. Do they ofen fail?
thanks

 

Intersting.

It looks like B8 detects, but does not turn on fans.
If the pressure switch and thermo sensor are closed, and the AC switch is pressed ('K') then B8 detects the ground on Blu/Red. This Blu/Red ground goes through the diode pack to close the relay for the A/C fan -AND- close the radiator fan. So both fans should come on when the A/C system requires them to (controlled by the thermo sensor when A/C is operating).

The Diode pack also prevents the ground from the radiator fan from triggering B8 and turning on the A/C. So the radiator can run 100% independently from the A/C at any given time.

B4 looks like it could give ground trigger to run the fans if it even needed to -or- maybe it just senses again.
It's not really clear what B4 does.

 

i used a normal ohm meter with no luck. I got open circuit all the way round. i don't have a diode setting.
I still can't figure out what that last plug is on the A/C harness. one goes to the cooling fan. one goes to the A/C pressure switch. I thought it was the CTS (cooling temp switch)connection. its not on the rad and i cant find it on the engine. its the same as the a/c pressure switch plug. but its a male
all three plugs come out of the harness at the same place (near the rad fan) and they are about 6" long.
have look at the blog http://1991civicsi.blogspot.ca/
i can't post any pics some how
bm

 

 

thanks for the write up. i'll dig back into the engine bay to have a look

 

The problem is solved.

when you install a A/C from another car it's pretty straight forward. There is nothing to tell you how to hook up the wires.

adding the A/C fan wires and the compressor wires was easy.
the other fan not so easy.
first off, it's uncommon to see an old civic with A/C in Canada,
second, the coolant rad is taken out of the car in the junk yards (in Canada at least) or the wiring is dis-connected. I for one car out of 7 junk yards with A/C wiring intact.

1. after installing your A/C wiring harness you will end up with 3 plugs near your coolant rad fan. dis-connect the white plug that is plugged into to green socket on your coolant rad fan.
2. take that same white plug and plug it into one of the 3 on your A/C harness (it will only go into one of them.(it's white)
3. take the green plug from the A/C wiring harness and plug it into the green socket on your coolant rad fan.
4. take the last plug on the A/C wiring harness and plug into the low pressure switch attached to the A/C hose (metal pipe)

when your coolant rad fan comes on so will your A/C fan.

I hope this helps others when they install there A/C

Cheers
Brent