A/C and Entropy Fans

[C10_ustacould]

I am installing a Vintage Air kit and my next step is to connect the trinary switch to control the compressor and the fan. Currently the #2 fan is controlled by the PCM in case the coolant temp gets to 226° and I like having that as a back up to the #1 fan that comes on at 195°. Has anyone configured their #2 fan to work when the A/C system tells it to (A/C on) and as a backup controlled by the computer? If so, how did you wire it?

[clinebarger]

Post #11 http://67-72chevytrucks.com/vboard/s...d.php?t=556348

[C10_ustacould]

Seems like the example in the linked thread is a little different situation than mine, but I did take something away from it. I should not allow my PCM to control fan #2. My fan relays are triggered by wires that look for a ground which is currently provided by the PCM. I should be able to disconnect the trigger wire for fan #2 from the PCM and connect it through the trinary switch to ground. Although I will lose the back up protection against overheating, this seems like the correct configuration for the A/C system. What do you think clinebarger?

[clinebarger]

Originally Posted by Bucks68

Seems like the example in the linked thread is a little different situation than mine.

How so?

I should not allow my PCM to control fan #2. My fan relays are triggered by wires that look for a ground which is currently provided by the PCM. I should be able to disconnect the trigger wire for fan #2 from the PCM and connect it through the trinary switch to ground. Although I will lose the back up protection against overheating, this seems like the correct configuration for the A/C system. What do you think clinebarger?

If you disconnect #2 fan control circuit.....The PCM will throw codes & Default to running #1 fan all the time.

Controlling one fan with two relays is fine & will work unless I missed something? Here the diagram again so you don't have to go back & forth.

[C10_ustacould]

CRAP!! I already cut that wire down and routed it to the trinary switch. So I guess I need to run another wire from the PCM and have it splice into the #2 fan trigger wire between the fan relay and the trinary switch? The problem I am having is integrating the two wiring diagrams in my head. My worry was the ground at the trinary switch goofing with the signal at the PCM, but it shouldn't matter because it is just waiting to give it a ground right? I'll give this a shot and we'll see how it works out.

[clinebarger]

Originally Posted by Bucks68

CRAP!! I already cut that wire down and routed it to the trinary switch. So I guess I need to run another wire from the PCM and have it splice into the #2 fan trigger wire between the fan relay and the trinary switch? The problem I am having is integrating the two wiring diagrams in my head. My worry was the ground at the trinary switch goofing with the signal at the PCM, but it shouldn't matter because it is just waiting to give it a ground right? I'll give this a shot and we'll see how it works out.

Splicing onto the wire will also do the same thing as cutting it, The PCM monitors that circuit at ALL times.

Can you read the above diagram? It shows a Separate Trinary Relay....For a total of 3 cooling fan relays.

[Hart_Rod]

Originally Posted by clinebarger

Splicing onto the wire will also do the same thing as cutting it, The PCM monitors that circuit at ALL times.

Can you read the above diagram? It shows a Separate Trinary Relay....For a total of 3 cooling fan relays.

Good info! Clinebarger you need to clean out your PM box....
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[C10_ustacould]

Originally Posted by clinebarger

Splicing onto the wire will also do the same thing as cutting it, The PCM monitors that circuit at ALL times.

Can you read the above diagram? It shows a Separate Trinary Relay....For a total of 3 cooling fan relays.

I guess not, I will study it more closely tonight. The issue I have is that the entropy setup doesn't just mesh with the diagram above. Thank for your help.

[Hart_Rod]

Ernie - leave your fans wired the way you have them (PCM controlled). Just add a third relay and wire it like like the diagram CB posted above. Just connect the red 87 wire to the power wire going into your #2 fan.
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[C10_ustacould]

This is a rough sketch of what my Fan harness looks like, the area in the red box is what I believe I should add based on the diagram above with the connection to the #2 fan being in the red circle. Make sense?

[Hart_Rod]

BINGO!
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[C10_ustacould]

Ok... Still don't want another relay though!
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[Hart_Rod]

Originally Posted by Bucks68

Ok... Still don't want another relay though!
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Bring it over Saturday and I'll wire it up for you, ...

[C10_ustacould]

I hope to have the truck running on Thursday, but I still need to find a new home for the computer and the fuse center. Not sure I'll be driving it anywhere this weekend, we'll have to wait and see how it goes.

[dayj1]

Originally Posted by Bucks68

Ok... Still don't want another relay though!

If you really don't want the extra relay, you can accomplish the same thing by adding a resistor and a diode to the circuit. Post 6 in this thread shows what I'm talking about:

http://67-72chevytrucks.com/vboard/s...d.php?t=590382

[C10_ustacould]

Thanks dayj1, I'll study on it and see which route I will take, but I do like the idea of not using another relay.

[68c10airstream]

Hi Buck, been reading some of the electric fan issues and would like to pass some past gm history along about electric fans. In the 80's i remember gm or possibly mopar had problems with overheating on front wheel drive electric fan applications. What would happen with a fan on the engine side (a pulling fan) is at about 30 mph and faster it would overheat. This was caused by a stagnant wall of air at the radiator, the end result of a fan not being able to pull the air in as fast as the air was coming through the radiator. I'm not sure of the fix, possible shroud change with shutters that would open up as needed on their own, but not sure. I just remember the situation. This could possibly not be a problem with a pushing fan on the outside of the radiator/condenser. Good luck, Brian F.

[C10_ustacould]

Thanks for all of the posts, I wired the trinary switch as it is in the diagram in post #10 and it works well. Thanks again guys!

[68c10airstream]

I should probably add that i believe gm/mopar are stopping fan operation at about 30 mph and higher so my point is i believe the pcm should be controlling the fan relays, to prevent overheating during this situation.

[C10_ustacould]

In my set up the pcm is controlling the fans, but because my computer doesn't know I have a/c I need the #2 fan to come on when the trinary switch senses the pressure/temp rise to the predetermined point. That is what I have now.

[Hart_Rod]

Sorry to bring up an old thread, but I have a slightly different question, but in think it is still relevant to this topic. My electric fan setup has a high rpm fan and a low rpm fan. It is very noticeable by the sound and the amount of air they pull. To my questions:

Question #1: which fan is considered the primary fan as far as the computer is concerned? high rpm or low rpm?

Question#2: which fan should I connect the trinary switch to? High rpm or low rpm?

I asked these questions in another thread but I didn't do a very good job distinguishing between hi/lo fan and hi rpm fan - low rpm fan.

Thanks in advance!
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[clinebarger]

Originally Posted by Hart_Rod

Sorry to bring up an old thread, but I have a slightly different question, but in think it is still relevant to this topic. My electric fan setup has a high rpm fan and a low rpm fan. It is very noticeable by the sound and the amount of air they pull. To my questions:

Question #1: which fan is considered the primary fan as far as the computer is concerned? high rpm or low rpm?

Question#2: which fan should I connect the trinary switch to? High rpm or low rpm?

I asked these questions in another thread but I didn't do a very good job distinguishing between hi/lo fan and hi rpm fan - low rpm fan.

Thanks in advance!

The Low speed fan is the primary fan (Comes on a lower temp).
The High speed fan is the secondary fan (Comes on at a higher temp...If needed)

On a Two speed fan, The Low is primary & The High is secondary.

I generally run the Trinary output to the high speed side of a Two speed fan, Though without knowing how efficient your A/C system/condenser is at shedding heat. It's impossible for me to tell you if the Low speed will be OK or not.
An OEM two speed set-up (Like Ford/Lincoln).....Turns the Low speed side ON as soon as an A/C request is made.....Then only engages High speed when Head Pressure dictates (250-275psi).

I forgot about your 6L80E dipstick issue.....I will try to remember to get some part #'s for you.

[Hart_Rod]

Originally Posted by clinebarger

The Low speed fan is the primary fan (Comes on a lower temp).
The High speed fan is the secondary fan (Comes on at a higher temp...If needed)

On a Two speed fan, The Low is primary & The High is secondary.

I generally run the Trinary output to the high speed side of a Two speed fan, Though without knowing how efficient your A/C system/condenser is at shedding heat. It's impossible for me to tell you if the Low speed will be OK or not.
An OEM two speed set-up (Like Ford/Lincoln).....Turns the Low speed side ON as soon as an A/C request is made.....Then only engages High speed when Head Pressure dictates (250-275psi).

I forgot about your 6L80E dipstick issue.....I will try to remember to get some part #'s for you.

Thanks for the info CB, that's what John at Speartech recommended also.

[jorgensensc]

What's the dipstick tube question? I might have an answer.

[Hart_Rod]

Originally Posted by jorgensensc

What's the dipstick tube question? I might have an answer.

I was trying to find one to work with the 6L80, since the one in the Camaro's doesn't come with one.