Tri5Nerd

iTrader: (3)

I'm using the stock 2001 LS1 fans and this diagram with the relay connections labled. Are these connection labled correctly?

Jones'n

Not sure what you are asking, but yes, that diagram is correct for the factory fan wiring.

Tri5Nerd

iTrader: (3)

I tooked the diagram and copied the numbers that's on the relay to the picture to the connection point that I think is correct , I'm talking about the numbers 30, 85, 86, 87 and 87a as it relates to the connection on the relay. I want to know if those are in the correct location.

Sorry for making myself clear.

Jones'n

Only one that looks wrong is Relay 3, looks like you have 87 and 87A mixed up.
Easy way is to look at the side of a relay, you will see the same diagram.

Tri5Nerd

iTrader: (3)

Then I have both relay #1 and #3 mixed up, both of them should have 87a instead of 87.

Is this correct?

Thanks for the help.

Jones'n

No, relay 1 looks right to me.

70 LS1

iTrader: (1)

I see two things. Yes you switched 87 and 87a on relay 3. 30 will be connected to 87a when de-energized and 87 when energized. A typical schematic always shows the relay in the de-energized state so you need to switch 87 and 87a on 3. Also on 1 and 2 you have 85 as + and 86 as -, but on 3 you have it the other way. It should work just fine as long as there are no diodes internal to the relay.

Tri5Nerd

iTrader: (3)

Thanks for the reply, I'll switch 87 and 87a on relay #3, then 85 and on 86 on #3 just in case there are internal diodes? I made the changes, take a look at this daigram and let me know if this is correct

G-Body

iTrader: (4)

Your a couple days ahead of me, I was going to post this tomorrow, but it looks like you could use it now


This is the way that GM hooks up the cooling fans for high and low speed. When the fans are on the low setting they are wired in series and each receive 6 volts, when the high speed relay kicks on the fans are wired in parallel and receive 12 volts. This hookup will work for all 98-02 f-body PCM`s, the relay terminal numbers are based on the standard bosch automotive style relays.

Relay # 1
terminal
86 to C100 pin J
85 to + IGN source (old HEI power wire)
30 to cooling fan fuse (size depends on amperage of fans) then directly to constant battery power
87 to + side of # 1 cooling fan

Relay # 2
86 to C100 pin H
85 to + IGN source (old HEI power wire)
30 to cooling fan fuse (size depends on amperage of fans) then directly to constant battery power
87 to + side of # 2 cooling fan

Relay # 3
86 to C100 pin H
85 to + IGN source (old HEI power wire)
30 to - side of # 1 cooling fan
87 to ground
87A to + side of # 2 cooling fan

the - side of cooling fan #2 goes directly to ground.

Tri5Nerd

iTrader: (3)

Got it!
This info should be added to the sticky for future reference.

G-Body

iTrader: (4)

Yeah, I was going to put it in the sticky, but I was working on a bit more and figured I would post it all at the same time.

lechner80

Can anyone show me how to wire up a 2 speed fan (3wires) with relays and the pcm control for high and low speed. Thanks John L

G-Body

iTrader: (4)

Relay # 1 Low speed relay
terminal
86 to C100 pin J
85 to + IGN source (old HEI power wire)
30 to cooling fan fuse (size depends on amperage of fans) then directly to constant battery power
87 to + low speed wire on fan

Relay # 2 High speed relay
86 to C100 pin H
85 to + IGN source (old HEI power wire)
30 to cooling fan fuse (size depends on amperage of fans) then directly to constant battery power
87 to + high speed wire on fan

Then ground the ground wire on the fan and your done.

lechner80

G-Body thanks for the info. that sounds easy enough. John L

LS1MCSS

iTrader: (18)

I am running and earlier f-body a/c compressor. How would I tie it in to this wiring to make the fan comeon with the compressor. My compressor is not hooked to the pcm anywhere.

G-Body

iTrader: (4)

I think that if you hook up the A/C request wire from your car (the wire that provides power to the cycling switch on the A/C accumulator) to the LS1 computer A/C request that the computer should see that you are running the A/C and turn the fans on. Try connecting the + wire on the cycling switch to C230 pin F, I have not finnished putting my A/C in yet so I am not positive this will work. If it doesn`t let me know, I have another way but it is not as simple.

LS1MCSS

iTrader: (18)

C230, would that be the red or blue connector of the pcm?

70 LS1

iTrader: (1)

I was just reading in the service manual about this. The PCM turns on the fans based on refrigerant pressure, not the A/C request signal.

When the PCM gets the A/C request signal from the HVAC module it (PCM) then turns on the A/C compressor. Once the PCM senses refrigerant pressure going up, it turns on the fans.

I think you are going to have to supply a signal directly to your fan relays when the A/C turns on. I'm not real familiar with A/C, but there should be some place on the compressor that goes hot when the A/C turns on. You can tap off of that and send it through a relay to supply a ground for your fan relays.

G-Body

iTrader: (4)

Well I guess I am not triggering my fans via the PCM, I was hoping the fans got the trigger signal when the A/C request was given but I guess I`m out of luck there. I`ll think about how to do it today, but I think triggering the fans directly will require either a relay and 2 diodes or 2 relays.

G-Body

iTrader: (4)

The only way that I know for sure that will work is to use 2 relays.
Relay #1
85 to the A/C request wire from your car (the wire that provides power to the cycling switch on the A/C accumulator)
86 to ground
30 to ground
87 tapped into the wire from the computer that controls the low speed cooling fans (C100 pin J)

Relay #2
85 to the A/C request wire from your car (the wire that provides power to the cycling switch on the A/C accumulator)
86 to ground
30 to ground
87 tapped into the wire from the computer that controls the high speed cooling fans (C100 pin H)

These 2 relays are in addition to the 3 relays that you will need to control the high and low speed fans.

I think that you might be able to use 1 relay instead of 2 and then use 2 diodes to isolate C100 pin J and C100 pin H and then put the output of the single relay between the diodes. But I am not positive that that will work and have not tested it yet so I don`t recommend trying it. Of course after reading the above statement I just realized that I probably confused everyone who read it unless they are electrical engineers in which case they would probably know if that would work.