jimmyd

Aux fan comes on around 210 or about, Main fan will not come on at all,
230 still no fan. I have a custom chip, It used to come on around 185 or so, best I remember. after new chip with 383 I haven't had any problems till now.
What controls the main fan ? or makes it come on ?
How can I jump it to make sure it still works ?
THANKS for any Help.!
:banghead: :banghead: :banghead: :cuss :cuss :cuss :confused:
OK...Both relays seem ok, switched em out, and got new one, aux fan works, Jumpeded A&B on ALDL, NO LUCK... Nothing...took fan out of car and hooked it up to 12 volts, IT works !, as prof from fingers bleading. :cuss
Now what ? could temp sensor on block be bad, IF so.. How do I test it ?
Possible ECM... :confused: :mad :cuss :banghead:
Life is good......Fun Fun Fun..


[Modified by jimmyd, 3:17 PM 7/17/2003]


[Modified by jimmyd, 3:27 PM 7/17/2003]

Strick

The main fan relay has four wires going into it. Two are heavier gauge wires and two are lighter gauge. Of the two lighter gauge wires, One is "run-on" power meaning it's hot when the key is in run and the other wire is ground, but it goes to the ECM where the ECM grounds it when it wants the fan to come on. To test the fan and relay just ground the ground wire that runs to the ECM with the key on. On my 92 LT-1 the color of the lighter gauge wires are: "run-on" pink with a stripe and ground to ECM is green with a stripe. I would guess that your wiring colors might be different so look at both primary and secondary relays and the lighter gauge wires. There should be two wires that are the same color going to both relays. That would be the "run -on" power. By process of elimination, the remaining wire would be the ground going to the ECM. Turn the key on and ground that wire to see if the fan comes on. Any help?

dpswmb

Just happen to see and have to leave without going through the reference books but just this thought for you. If you know the relay works, check the connector for 12volts at the relay. The connector is just a ground and power. So, if you have 12 volts at the relay connector and a good relay too then I would think the fan is bac or has a bad connection. I don't recall how the fans are on my 90 but I know the fan on my 84 also has a connector. If the 88 does then you can check this connector for voltage too. Or, jump the fan directly with it disconnected?

I vaguely remember that ALDL connector can be jumped (A to B) and both fans should come on--think this was the first step in troubleshooting. I will try and get back to you later but son getting married. Hopefully others will have solved you problem by then.

HeeHaw89

I think I have a similar problem The fan that is on the backside of the radiator comes on intermittently. Is that the main or aux fan? Sometimes it comes on at 200* as the chip is programmed for. Other times it will not come on. Could this be a related problem as the original poster?
It is easy to determine if its working properly because if my coolant temp hits 200 and soon goes down its working. But many times recently it will hit 200 and keep on going up, one time up to 260! I popped the hood to find that the fan in front was running but not the one in back.
I left the key on so at least the one fan would cool the car and when coolant temp hit 228 or so the front fan turned off. What should I be looking for?


[Modified by HeeHaw89, 9:18 AM 7/17/2003]

jimmyd

OK, thanks guys, Going to go try again, I'll report baxk what I find.
:smash: :cuss :chevy

dpswmb

This is not good for me to shoot from the hips but I am running ragged trying to get to my son's wedding out of town. Assuming all wires (the fusible links too-my 90's are behind the battery and my 84 on the battery post), connectors, sensors and THE ECM work, if no fans then I would have to believe fan motors are bad. However, I would think it odd for both to go out but they could.

The most discrete check to see if the fans really do work is to jump the A wire (should be the first wire on end and probably black) on the ALDL to the B wire which is right next to it. Just mess with this jump connector and if the fans run then you know they are okay. Provided you are getting voltage at the relays then the relays could be bad. Think relays can be gotten at most parts places and still from Chevrolet dealerships for around $15. I also believe the red wire on the relay connectors comes from the fusible links by battery--no 12 volts probably bad link. Worst case if none of this does any good is to suspect the dreaded ECM signalling??????????? Cannot help you there. Just be methodical and make sure voltage is there and relays really are good and connections good. Best of luck and wish I had time to provide more and possibly more accurate and helpful info.

Maybe you can help heehaw out or someone else can. The unit on the front radiator side (primary and seconday fans and each has a relay) is setup to come on bewteen at "x" temperature or A/C on (primary). Then if the ECM senses the primary on and A/C running and less than "y" miles per hour then I think the seconday comes on. Best I can do-----------bye for several days and hope I don't cause yours cars to quit running!!!!!!!!!!!!!!!!!!!!!! bill :auto:

jimmyd

TTT, see above.....

oldace84

Were any sounds comming from it before it quit??????
Does it spin by touch??????
Good Luck
tony
:eek:

jimmyd

Didn't notice any. With fan out of car it will work. so it seems ok, Just not coming on in car.

88Vert

I had a problem with my fan and it turned out to be the ECM. I had other symptoms too such as my 4+3 didn't shift into OD correctly, the instant & average MPG acted funny or didn't calculate.

I picked up an ECM from the boneyard for $45. You might want to try it. Used my own chip of course.

Good luck!
:cheers:

65Z01

Since the fan & relay are ok, open the connection in the A/C pressure line in front of the blower motor housing and start the engine. The main fan should immediately come on as the ECM sees a high pressure condition in the A/C line.

If that works, check the coolant temp switch in the front of the block below the TB. If it reads a high impedence when hot the ECM will think the coolant is still cold and not bring the main fan on.

Also, since you have an aux fan, you could use my C4 Tech Tip to wire the main fan to be turned on by the aux fan switch or by the ECM. Of course this works if the aux fan switch On temp is at or below the main fan On point as determined by the CalPac.

dpswmb

Jimmyd----I forgot to tell you to watch your fingers or anything else on your front body which may be hanging in the way of the fans---------oh, too late huh? Just checking back in but it sounds like time to drink a beer and clear mind. Once you do this you can again realize that your problem hasn't gone away. Sometimes I think I should just put a fan blade, pulley and belt on my cars? High pressure check hopefully will turn over a rock which will cause you to turn over another rock. Please let us know how you solve this caper!

jimmyd

I've got an idea it's the ecm, But, I've had enough fun for today, Im gona check the temp sensor next, 65Z01, what would a high impendence be ?
Some of this stuf Im chasing my tail, cause Im not exactly sure what im doing. (example-- holding the fan with one hand wile puting juice to it, tried to catch it when it jumped out of my hand.)
Also....Are you talking about the AC line at the top of heater core where the plug is facing up ? Or their is a couple of plugs down lower, one has 1 wire or the other has 2 wires ?
I gota get some sleep, I'll try again tomorrow, at least its on jack stands now where I can get under it somewhat, Going to take the radiator out wile im at it, Its stoped up pretty good.
Thanks again, everyone !!

dpswmb

Very late and too dark to go look at my cars right now. Just one more thought for you before you go and try and replace the ECM if the temp sensor is good. Very possibly you could just have a bad ground on the fans? I am sure that your fans are like my 84 fan which only has two wires--one is for power and the other is for ground. The relay takes care of sending power to fan when it receives signals from the ECM via sensors--i.e. receives high temperature, relay circuit closes and sends 12 volts to fan and then the power is returned to ground from the fan. I suspect the ground point maybe somewhere on the front left rail? Why don't you make sure battery cable(s) are disconnected and do a continuity check on the front male connector which goes directly into the fan. There will only be two wires and only one should give you continuity on your voltmeter--try each wire at the connector and just ground it to the motor or frame or some good point. If you cannot get continuity this way then you most likely have a bad ground wire or bad ground connection. Or, if you know exactly where the grounding point is for the fans (I am not sure) then just check continuity from the ground point and the connector--then you will absolutely know for sure. I really hope this is your problem as it would be real easy fix and things would just start working most likely. CYA Later

Ray Quayle

I wonder what is the maximum impedence you would expect to see in a DC circuit? Z=E/I? That's not how I remember it. Mr. Ohm is rolling over in his grave. :D

jimmyd

Update: Cleaned radiator, lots of trash ! Still no fan, Im not real good with this testing meter.
When I tested the fan out of the car, It has a two wire plug, I would think that one would be hot - the other ground,
to get the fan to work- I had to put a hot (12v) to the plug and groud the fan housing, That couldn't be right could it ?
With the fan mounted in car, their is no way to groud the housing because its mounted in plastic. Right ?? I gota go re check this, That was 3 days ago.
I could be wrong about this.........daaaa..... :confused:
Oh--Oh.....saftey tip..before I forget...On the hood prop rod- stick a screw driver or somethin down in to the prop tube, so the rod is to one side where it can't move, If rod is bumped wile working under hood it can move, whitch causes the hood to FALL, and that is not FUN, I Promise....