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Old 07-27-2010, 11:31 PM
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LT1 dual Fan problems -- continues!

hey guys,

thanks to your help so far, you helped me figure out that the fans in my 96 impala SS lt1 to jaguar xj6 conversion are live -- i re-wired the harness from the fusebox directly to the fans, and when i jumped the relays directly from the battery, the fans turned on. Great!

however, the fans are not turning on on their own. not only do i have a check engine light (which forces the fans on), but when i unplug the sensor from the water pump (another way to force the fans on) i get nothing as well...

what could it be? i tried a new relay for the primary fan (only had one new one), and for the secondary, still no results. what should i try next?

thanks!

tyler

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Old 07-28-2010, 01:55 PM
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could i try grounding the relay control wires in the fuse box to the negative battery post?
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Old 07-29-2010, 05:34 AM
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not sure if this will help but heres a site for LT1 camaros diagrams http://shbox.com/1/schematics_wiring.html
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Old 07-29-2010, 07:40 AM
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Cooling Fan Relay #3

Hey Tyler, Sounds like you don't have Cooling Fan Relay #3 in your under hood fuse box or if you do, it may be bad.

The later systems used a third relay to series the fan motors for low demand cooling.

With the ECM output on for low cooling, the fan motors are connected in series and both run at half speed.

With the ECM output on for high cooling, the fan motors are connected in parallel and both run at full speed.

Without Cooling Fan Relay #3, they won't run at all.

If your under hood convenience center is the same as a Camaro;

Left to Right- A set of 8 fuses on left, then 8 relay slots in the middle, then a set of 4 fuses on the right.

Left to right - Second row, first fuse #6(10amp) is the fan actuator fuse.

Left to Right- First row, second relay is Fan relay#1(relay position D)
Second row, first relay is Fan relay#2(relay position F)
Second row, fourth relay is Fan relay#3(relay position J)

If you still have the cover for the under hood convenience center, you'll see what I'm talking about.

Sounds like a cool project, post photos. olnolan
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Old 07-29-2010, 11:09 AM
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hmm, in my row with the relays, one of them is listed as AIR PUMP, then PRIMARY COOL and SECONDARY COOL... should i swap out the Air Pump one? I don't have the Air Pump connected/installed...
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Old 07-29-2010, 02:24 PM
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Early Production

Hey Tyler, You must have the early production setup.(No relay#3) Can you post a photo of your under hood fuse/relay box and the cover legend? I might be able to help you troubleshoot it. Its hard to do over the internet, but I'll try if you have the patience. olnolan
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Old 07-29-2010, 03:16 PM
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hey man,

sure, i got plenty o' patience... just serious difficulties in getting the darn thing to kick on ;-)

http://www.lt1swap.com/pictures/fuse...icker_1024.jpg

thats what my under-hood fuse block looks like....

i've heard that it could be PCM or Temp sender related... if its temp sender related, i was wondering if there is such a thing as a sender that has a different temp to turn on fans (lower). I saw some stuff on Jegs, but it looked different from the sender i had. if it is PCM related....doh!
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Old 07-29-2010, 05:06 PM
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Diagram



Ok Tyler, I don't know what part of the circuit you re-wired, but if its not wired like this, the PCM is not going to turn them on.

As you can see on the diagram and your fuse box cover, there are four fuses and two relays involved.

So, tell me from the diagram, what wires did you mess with.

Nolan
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Old 07-29-2010, 05:31 PM
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i bought the Primary fan harness kit from innovative wiring -- the only wires i had to replace in the fuse box was the Blue Wire and the Brown wire (these are the pins that if i apply 12V directly from the battery, they will activate the fans, when i have the relays popped out). These wires go straight to the fans, replacing the old fan wires that i had from before. these wires on this sheet are 532 and 409...

As for the relay control wires, on this diagram, wire A10 (dark blue) and A11 (dark green), i depinned these two wires from the PCM connector (on my harness it is the red connector), and when i grounded them individually the fans came on (when i had the relays plugged back in the fuse block).

I've since repinned the connector and put it back together, but the fans still fail to come on at any temp. Does that help any?

Last edited by tylerwerrin; 07-29-2010 at 05:41 PM.
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Old 07-29-2010, 05:54 PM
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Ok

So the harness you put in was just the c103/c104 portion?

If everything works by grounding either A10 or A11 then you may have a PCM ground thats open/not connected.

Do you have the PCM pinout diagram for all four of the PCM plugs?
I poked around online and haven't found one, all I have is the F body stuff and it seems some of it is different.

The PCM does have multiple grounds, like a ground for a certain group of drivers, then another ground for another set of drivers, so on and so forth.

If you have the PCM pinout diagrams, post them so we can find all the grounds.

Nolan
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Old 07-29-2010, 06:53 PM
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i'll get a scan of the electrical sheet tonight after work. it has to be related to the sensor in the water pump (which doesn't make sense why it'd go bad, when it still is giving me readings while i do diagnostics on it (thats where i watched the temp climb to 260, before turning the car off.)

Is there a software that actually shows that the fans SHOULD be running? if there is, i'd be able to tell if the sensor is actually sending the signal to the PCM to ground...
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Old 07-29-2010, 08:26 PM
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Temp Sender

Hey Tyler, Sounds like if your scanner is seeing a temperature increase then we don't have to test the sensor, the input to the PCM is satisfied.

I'm leaning toward ground output issues with the PCM. If it doesn't have a ground at the right ground input,then there is no ground for it to output(to turn on your fan relays).

See if you can find the PCM pinouts for the B-body,then we can test the ground inputs. The F-body pinouts I have show 4 different ground inputs on 3 of the 4 plugs. There is no way I can verify that the B-body pinouts are the same, so we could end up troubleshooting ourselves around in circles.

If you can't find them then we can check from the F- body stuff and maybe find it? I have a good feeling we are closing in for the kill.

Nolan

Oh, About the water pump sensor, I'll have to try and find a input loop sheet to be sure, but I think it is just a flow switch, all it does is turn on the low coolant light if your water pump is going bad(cavitating). I'm pretty sure thats the arrangement on the LS engines. Maybe LT1 too.

By the way, have you bled the air out of the coolant system to make sure all the sensors are flooded in coolant. The LT1 will trap air until you open the bleeder valve and run the engine until all the air is burped out.???

Last edited by OLNOLAN; 07-29-2010 at 08:43 PM.
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Old 07-29-2010, 09:00 PM
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96 Lt1 connector 1 pin11 dark green primary cooling fan ( ckt335)
connector 1 pin 10 dark blue pin10 secondary fan (ckt 473)
pcm connector 1 is the red one
This is from a reliable source. Hope this helps
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Old 07-29-2010, 10:34 PM
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hey nolan, which pages would we need to check this? there are several different pages in here...

and i think all the air has been burped out, i opened the bleeder valve on the T-stat housing while the car was running until only coolant dribbled (then sprayed) out. Unless there is another way to remove trapped air...
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Old 07-29-2010, 11:13 PM
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are these what we are looking for?
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