Electric fan control confusion

[NC_John]

I am having the strangest problem with the control of my electric fans and unfortunately I am the best controls guy I know so I don't have anyone that can come over and look at this.

Lsx swap.
Speartech harness.

I've got two pair of wires coming from the speartech harness to control my fans (primary and secondary). I have each of these signal pairs wired to bosch relays on pins 85 and 86 (coil terminals) (this is also as speartech instructs). I have 12 v (constant) directly from the battery wired to terminal 30 on the relay. Power to the fan is from 87 (the normally open side of the relay). Pretty basic stuff.

Here's whats got me beating my head against the wall.

The fans simply won't come on.

When the engine reaches temp (don't recall the setpoint we put in hptuners), i am reading 12 vdc across the wires coming from the harness using my fluke multimeter- so the pcm is indeed calling for the fans to come on. BUT it won't trip the relay when connected. When I measure the 12vdc from the signal pair and then plug in the relay it doesnt trip.

I tested the relay and can trip it using jumpers to the relay with power directly from the battery. Its a decent "click," meaning the relay seems healthy. I also checked resistance across 30 and 87 with an ohmmeter when I cycle the relay and it works fine. I can engage the fan when I jump 30 and 87 (bypassing th relay). So everything logic-wise seems correct. I have confirmed the terminal positions on the relay and the relay harness. They are correct.

I had everything soldered and heat shrunk but i thought the problem could have been in the relay harness so I reluctantly cut my connections and put new crimpons on the four wires, thus bypassing the relay harness and its connections. Didn't help.

I am wondering if the signal from the pcm just doesn't have the nuts to trip the relay but that doesnt make a lot of sense. Speartech instructs to wire each of their pairs of control wiring so it must be strong enough of a voltage signal. I even tried to measure the current but couldnt get a reading with my meter. I'm using a bosch 0332209150 relay 12V/20/30A.

The only thing left I can think to try is to buy another brand relay and see if the pcm can trip it.

Ideas? Anyone?

[mongocanfly]

I had issues with my fans when I got up and running....the ecm wasn't designed to run dual fans and it had the whole thing messed up...they had to go back into the program and change something....

[NC_John]

Originally Posted by mongocanfly

I had issues with my fans when I got up and running....the ecm wasn't designed to run dual fans and it had the whole thing messed up...they had to go back into the program and change something....

I don't think thats my problem. I'm getting a fan-on 12V signal. For some reason, the relay just won't engage.

I went to autozone and got a different relay. Did the same thing. Pretty frustrating. I can go ahead and get the entropy fan controller but I want to understand what the heck is going on with this setup.

[87chevy.com]

Originally Posted by NC_John

I don't think thats my problem. I'm getting a fan-on 12V signal. For some reason, the relay just won't engage.

How do you know your getting 12v fan signal?
How are you measuring it?
The pcm supplies ground to the relay. The + wire is a strait power or ignition depending on how the harness was made. I would measure battery post - to the " + " from the harness and see what you get. Try no key, key ignition on. Do that for both " + " wires. Then battery post + to the wires marked " - " and then use hp tuners or equivalent to activate each one to verify pcm is giving the on signal.
Post up what you find.
Clint

[NC_John]

Originally Posted by 87chevy.com

How do you know your getting 12v fan signal?
How are you measuring it?
The pcm supplies ground to the relay. The + wire is a strait power or ignition depending on how the harness was made. I would measure battery post - to the " + " from the harness and see what you get. Try no key, key ignition on. Do that for both " + " wires. Then battery post + to the wires marked " - " and then use hp tuners or equivalent to activate each one to verify pcm is giving the on signal.
Post up what you find.
Clint

I think you’re on to something. I was measuring 12 VDC with my multimeter directly across the relay control pair provided by speartech. I knew the PCM was switching grounds but for some reason, since the harness provided a pos and neg for each set didn’t consider it.

I had to leave the house at o-dark-thirty this morning but still took a second to throw the meter across the same pair I have been testing with the engine cold (and therefore no fan enable signal). Still got 12 VDC across my meter.

I’m going to test across the battery this evening but now I bet the PCM isn’t sending the fan on signal I thought it was. We enabled electric fans in HPtuners when we were tuning but couldn’t test it (or didn’t think to) on the dyno. I don’t yet own my own copy of the software yet to test it at home. I might see if I can borrow a tech 2 (or similar) and see if I can trigger them that way.

Otherwise it’ll be easier just to buy the entropy controller and move on to the next bug in the build.

Thanks

[87chevy.com]

In a pinch, you could run a ground switch to the pin 86 of the relay if the 85,+, is good that would allow for temporary manual control if you had to drive it

[NC_John]

Originally Posted by 87chevy.com

How do you know your getting 12v fan signal?
How are you measuring it?
The pcm supplies ground to the relay. The + wire is a strait power or ignition depending on how the harness was made. I would measure battery post - to the " + " from the harness and see what you get. Try no key, key ignition on. Do that for both " + " wires. Then battery post + to the wires marked " - " and then use hp tuners or equivalent to activate each one to verify pcm is giving the on signal.
Post up what you find.
Clint

I ran the 12V signal from the speartech harness but ran a ground to the other side of the coil directly from the chassis. The fan came on. So that's what the issue is- despite what I am reading on my meter, the PCM is NOT calling for the fans to come on.

The only thing leaving me puzzled is how I am getting a 12 VDC reading off my meter if, by my understanding, the ground should be switched off at the PCM. Where is it getting the ground to read the voltage?

[ls1nova71]

Originally Posted by NC_John

.
The only thing leaving me puzzled is how I am getting a 12 VDC reading off my meter if, by my understanding, the ground should be switched off at the PCM. Where is it getting the ground to read the voltage?

I have never personally messed with a Speartech harness, but know they are a good quality harness. If you are in fact testing the terminals 85 and 86 and getting 12v, then your fans would be on all the time. I suspect you are testing something else. What exactly do the instructions say about wiring up the fan relays? Can you post a pic of the way you have it?

[87chevy.com]

Edited..

[mongocanfly]

Did you check your grounds?...might try ground wire from relay to the battery and see if that helps

[NC_John]

Originally Posted by mongocanfly

Did you check your grounds?...might try ground wire from relay to the battery and see if that helps

Not a bad idea. I'll do that.... not today - i'm done playing out there in the heat for today.

Thanks

[BR3W CITY]

Originally Posted by NC_John

I've got two pair of wires coming from the speartech harness to control my fans (primary and secondary).

Just a dumb question since I can't read inflection on the forum. Are you referring two 2 wires, or 2 pairs of wires ( 4 total)?

[NC_John]

Originally Posted by BR3W CITY

Just a dumb question since I can't read inflection on the forum. Are you referring two 2 wires, or 2 pairs of wires ( 4 total)?

Two pair of wires. Four total. One + and one - for each fan.

[sprint_9]

Disregard

[Custom 68]

I am trying to remember but I thought the fan signal was actually negative (ground) rather than the 12 volt positive. So they get wired up differently. I think I have 12 volts going straight from my battery (fused) then the ground comes from the relay which is tripped by the PCM. Now I am going by memory and it has been 12 years since I did my original so I may have my self crossed up. I just remember something was different than normal. I will do some looking and maybe find something tonight in my notes.
Does any of this rambling sound right to any of you real ls geniuses?
Dave

[NC_John]

[QUOTE=Custom 68;8288727]I am trying to remember but I thought the fan signal was actually negative (ground) rather than the 12 volt positive. So they get wired up differently. I think I have 12 volts going straight from my battery (fused) then the ground comes from the relay which is tripped by the PCM. Now I am going by memory and it has been 12 years since I did my original so I may have my self crossed up. I just remember something was different than normal. I will do some looking and maybe find something tonight in my notes.
Does any of this rambling sound right to any of you real ls geniuses?
Dave[/QUOTE

you can certainly do it that way, that's how my trinary switch got wired, but with speartech, they provided both the + and ground wire from their harness.

[Custom 68]

ok I re-read the other responses and looks like that was pointed out. but here is a diagram showing this as well.

[dec010974]

As i look at the diagram on post number # 14, if it were my vehicle, i would rewire the relays. #30-12V+Battery #85-12V+Ignition #86-PCM (ground) #87-12V+ to Power Fans on the +side. Add (-) ground to negative side of fans. This is just my .02 cents. Im no expert. Good luck.

[Super73]

Originally Posted by NC_John

I've got two pair of wires coming from the speartech harness to control my fans (primary and secondary). I have each of these signal pairs wired to bosch relays on pins 85 and 86 (coil terminals) (this is also as speartech instructs). I have 12 v (constant) directly from the battery wired to terminal 30 on the relay. Power to the fan is from 87 (the normally open side of the relay). Pretty basic stuff.

Relays are a remote switch. 85/86 are internally connected through a coil. Either 85 or 86 should have 12v than the other pin should be grounded through the ECU.

If 85 has 12v than 86 to ECU
if 86 has 12v than 85 to ECU

The ECU is completing the ground.


When you complete the 85/86 circuit, it switches the high current power between coming in on 30 from 87a to 87

30 has 12v in

87a is normally closed meaning 12v power will be on that pin until 85/86 circuit is completed

When 85/86 circuit is completed power will be switched from 87a to 87


So you want 30 to have a fused 12v
87 goes to the fans input
Fan output gets grounded


Now if you are retaining AC with a factory computer, you should be running a 3 relay set up. This will turn the fans on in series so the each see 6v (half of normal) to spin half speed (or there about). 2 reasons for this.

You want the fans moving air across the AC condenser so it does not freeze.

If fans are running half speed while AC is on, they require less amperage draw to kick up to full speed when the ECU command high speed. Too many people wire a 2 relay set up with AC and wonder why their vehicle either dies or the electrical system dims hard when AC is on and fans kick on. It takes a lot of initial current to get the fans started.

[NC_John]

Originally Posted by Super73

Relays are a remote switch. 85/86 are internally connected through a coil. Either 85 or 86 should have 12v than the other pin should be grounded through the ECU.

If 85 has 12v than 86 to ECU
if 86 has 12v than 85 to ECU

The ECU is completing the ground.


When you complete the 85/86 circuit, it switches the high current power between coming in on 30 from 87a to 87

30 has 12v in

87a is normally closed meaning 12v power will be on that pin until 85/86 circuit is completed

When 85/86 circuit is completed power will be switched from 87a to 87


So you want 30 to have a fused 12v
87 goes to the fans input
Fan output gets grounded


Now if you are retaining AC with a factory computer, you should be running a 3 relay set up. This will turn the fans on in series so the each see 6v (half of normal) to spin half speed (or there about). 2 reasons for this.

You want the fans moving air across the AC condenser so it does not freeze.

If fans are running half speed while AC is on, they require less amperage draw to kick up to full speed when the ECU command high speed. Too many people wire a 2 relay set up with AC and wonder why their vehicle either dies or the electrical system dims hard when AC is on and fans kick on. It takes a lot of initial current to get the fans started.

My A/C is vintage air so I have a triggered ground coming from the trinary to a third relay which activates the primary fan.

I'm confident the issue is solely within the PCM controls and since its going to be a pain in the buttocks to troubleshoot without HP Tuners, I am just going with the Entropy fan controller setup, triggered by a temp sensor in their radiator. I ordered it today. Its pretty slick, ramping fans up and down as needed and taking my A/C ground signal to tie-in the vintage air.

Its just a bummer I spent so much time wiring, soldering, heat shrinking my initial setup. The good side is removing all that stuff makes some room for a potential cold air intake on the drivers side (I'm mounting the entropy components on the other side, under the battery)

[NC_John]

Follow up and conclusion.

I bought the entropy dual fan controller setup. It is a very, VERY nice package and I got it installed (and tested) yesterday. It is a lot of wiring, heavy gauge at that, but I managed to mount the controller and hide all the harnesses under my battery tray so they are out of sight. In fact, its a cleaner install than the initial pcm relay nonsense and wiring I put together on the driver side.

When the coolant (measured through a radiator mounted sensor) reaches the first setpoint, both fans come on at 50%. I couldn't even hear them. When setpoint 2 is reached they ramp up to 100%. Temp settings are adjustable through dip switches but right now I don't see any need to change them.

The controller has inputs for air conditioning as well, either a +12V (didn't use) or a ground signal from the trinary switch (used this one). As soon as A/C is requested the fans kick on.

The only other wiring is an ignition on 12VDC power supply and a ground.

This is a much better solution to me than trying to sort all this out through the mechanical fan blue/green truck pcm. I should have just gone this route in the first place.

I have been very happy with the entropy package. Its not inexpensive but this is a great example of you get what you pay for.

[mongocanfly]

Good to hear ya got it fixed....

[NC_John]

Originally Posted by mongocanfly

Good to hear ya got it fixed....

Thanks. It was definitely a big item to get sorted out.

I appreciate you guys helping out.