Hey yall - first post here. Gotten a ton of info out of this website/forum so first off THANK YOU.

I have a 1986 with a 4.9L (and factory A/C) I’ve just gutted the EEC electrical on in prep for a Duraspark II conversion. Clifford intake and EFI exhaust ready to be installed. Holley 390 carb too. I have a few questions about some rogue connectors after ripping wiring out. From what I’ve read, the computer only controlled emissions and carb stuff. When I ripped out the harness, I was left with these:



This was on the backside of the accumulator/dryer.



This comes up from the alternator I believe.



This is attached to battery negative - is this ground for the computer I no longer have?



This has to do with water temp sensor?

I would love to know what these do and if I need to wire them up somehow? As I said, the entire EEC wiring harness has been ripped out. I have the ignition harness from a 1983 along with it’s dizzy, coil, and Duraspark II unit ready to go. The ‘83 harness has water temp, oil pressure, and tach wires built into it so should be good there.

Any help greatly appreciated or link me to another thread with answers if you know of one!

 

This was on the backside of the accumulator/dryer.
This connector plugs into the low pressure switch for the A/C system. There was a relay in the computer system that disconnects the A/C compressor when you are at WOT. If you want your A/C to work, you will need to do a little wiring and hook this back up.



This comes up from the alternator I believe.
This is most likely for the electric choke. Especially if the wire is white/black stripe.



This is attached to battery negative - is this ground for the computer I no longer have?
Most likely yes.



This has to do with water temp sensor?
If this sensor has two terminals, yes it was the temp sensor for the computer. You will have another one somewhere else with a single terminal for the dash gauge.

For anyone else happening upon this thread, the easier way to do this is to start under the dash and take the computer out first. Unplug the large wiring connector and poke it through the firewall, leaving all those wires connected. Then slowly one by one unplug the connectors and cut just a wire or two. Once this large plug is free from the engine bay, you have gotten everything hooked to the computer.

 

Will my AC compressor not kick on at all if that wire/connector is left disconnected? If so, where/how does it need to be wired to have the system function properly? Does feeding it 12V kill or kick on the compressor? Thanks!

 

I may have miss-spoke here. I should have looked at the diagram. The EEC did not have a interlock with a relay. It looks like the EEC just tapped off the A/C system. When the A/C was activated, it told the EEC that the A/C was turned on, and most likely raised the idle speed. If you have a lightgreen/pink wire coming out of the firewall, going to the low pressure switch, and then a black/yellow wire leaving the low pressure switch going to the A/C clutch, I believe your A/C should work if it did before the swap.

 

DaveF that is the first I have heard of the WOT killing the compressor and I dont think I have heard of others doing this swap needing to deal with this
Do we have any wiring on how this was in a truck? That would tell us how it tied into the AC wiring / system. (I was having breakfast and started this reply before)
If what DaveF is saying was this plugged into something and did the AC work before doing this work?
You know like "Doc will I be able to play the piano" after his hand got crushed and he could not before, type of thing

I think the only way to know is to try if the AC works or not and test if that wire has any power anytime the AC is on.
My truck is pre-feedback so no computer but there is nothing to tell the AC that I am at WOT and again first I have heard of this on any motor in our trucks.
Dave ----

 

Thanks Franklin2 - that diagram helps. Looks like in pre EEC vehicles, that same pigtail goes directly to the TPS (most likely to do what you said - bump up idle). I suppose they just sent it to the computer instead to then talk to the TPS. Middle man shenanigans.

I’ll have to clean up the wiring and see if I can tell what the colors are. I definitely see a black and what appears to be a yellowish/greenish looking wire going to the low pressure switch. The A/C did indeed work fine before yanking everything out. I wonder if just bumping the idle up in general might remedy any sort of engine load issue the EEC was trying to fix when the A/C kicks on. It gets HOT here in TN and it’s definitely nice to have climate control. Thanks for the info!

 

Haha I like that analogy as a musician myself! Yes the A/C worked before yanking it all out (compressor was starting to fail though and I need to replace it along with accumulator, oriffice tube, o-rings…something I’ll tackle in the spring).
I’ll leave it as is and test everything once I get the truck finished and running but I believe after looking at that diagram I’ll be A-OK. Also, you saying you haven’t heard of anyone addressing this who’s done this conversion makes me feel more confident as well

 

You may not need to do anything with the idle speed when the compressor is running.
I say this because I dont have a solenoid that kicks the idle speed up when the AC is on and dont have any problem of the motor stalling and my idle speed is about 650 / 700 RPM and been this way for years.
Now I do have a manual transmission so I dont know if that makes a difference or not?

Also with the feedback system if the carb did not have a solenoid to bump the idle speed up how would the computer do it?
The computer from what I have understood only makes the carb rich / lean based on what the o2 was reading.
Was not till EFI that they got a IAC to change the idle speed from what I know.

Just thinking here but I am sure you will be ok and the AC will work if it did before you may just need to bump the idle speed up a tad.
Dave ----

 

My AC still worked without the computer.

There's a fast idle solenoid mounted on the carb that's controlled by the computer, it wouldn't work anymore. I normally just used the AC on the freeway.
At a stop light, sometimes I would shift to neutral to increase idle speed.
As you have a G2 alternator, you will also have to do this to keep the lights from diming and the heater fan from slowing down at a stop light. The 3G alternator was a big improvement.
Jim

 

Remove the tape and take a picture of this splice.
Do you have 3 wires or 2 wires on the firewall side?

Original DS2 trucks had 2 wires in and 1 wire out.

Jim

 

Reference post 1, photo 1:
The connector you are holding in your hand is what told the computer the AC was ON.

Another suggestion is to install a couple of washers between the plastic inner fender and the DS2 ingition module. This will give air flow under the ignition module, to help it run cooler.

Jim

 

I will have to see where the power to the solenoid comes from on my truck but I want to say it TEE's off the wire going to the compressor as it would be "12 volt hot" when AC was on.

My truck uses a G1 ALT and other than when I first start the truck and pull it out of the garage I stop to put on my seat belt is that only time I see the head lights dim at idle.
Once the battery has had time to recharge from starting I dont get any of the dim head lights or AC / heater fan slowing down.
I dont know the AMP output and it may not be for AC but there is no need to up what I got as it worked good from the factory.

Just so you know I do run a head light relay kit so the head lights are pulling a full battery volts when on.
I also have fog / driving lights in the bumper on relays but still dont see the lights dim or fan slowing and they were all on with AC and wipers yesterday in the rain when I did my weekly trash run.
Dave ----
ps the radio was also playing so that was a good load on the system.

 

The computer controlled the idle speed by a DC motor mounted on the carb throttle linkage. In the same place as the old school solenoid, but it's much larger with more wires. It controlled the fast idle during warm up except the very fastest initial speed, which still had a notch on the fast idle cam. It controlled the idle speed at all other times also.

You can turn up the idle speed a little bit to improve A/C performance. It's not there to prevent stalling, it's there to turn the A/C compressor faster so it pumps the refrigerant around better, and also increases the fan speed of the engine which helps pull more air through the condensor for the A/C, and of course helps the engine run cooler with more air through the radiator and the waterpump is turning faster.

I had to do the same thing, increase the idle speed, when I put a snowplow on my F150. It had the original 60 amp alternator, and when it was at a slow idle, it would not pick up the plow. I just got under the hood and turned the idle speed up a little bit and it picked the plow right up. It wasn't a increase that caused any other problems, so I just left it like that.

 

I’ll do ya one better - bought some rubber grommets, longer bolts, and steel spacers to lift it off the fender well. May even look into installing a small fan tee’d off of ignition hot to keep it ultra cool .





Is there a way to bench test Duraspark units? I read you used to be able to take them to auto stores and they had a device to test them… none of them know what the heck I’m talking about when I call them though

 

I think that’s what I’ll do. Would you suggest between 800-900 idle RPM?