Hi folks,

I am having problems with my primary fan NOT shutting off.... it comes on as soon as i turn the key on... it worked fine last year , I have tried lowering the setting in the prom but the fan is unresponsive, it just keeps on running, i do NOT however have a SES light and i have tried loading other bins into the car and i still get the same problem...any help would be greatly appreciated....thanks sean

 

Have you tried the stock prom by itself? Sometimes a bad eprom/flash prom can cause this.

Also, is your A/C on? If so, that's your problem.

 

i'm haveing same issue, prom was changed 30 times (stock and modded) but every time i start the engine fan goes on.

 

Have you guys checked the fan system itself, including the relay and for chafed/grounded relay control wire(s)? If changing the bin doesn't change the bhaviour, I'd have to suspect something else.

 

when relay is disconnected only primary fan is working non-stop and secondary starts depending on temperature, when i plug it back both starts and work non-stop when engin is on

 

Grim, Hi!

Thanks for the reply, the AC is not on I have checked and verified this , I have tried a stock AUJP with no difference, I will however swap the prom out tonite and upload the current bin to a different prom and see if it goes away.
It is really frustrating as the car is still in storage i just moved it out of the way a few times this spring and everthing was normal, a few days ago i agin moved the car and noticed that when i turned the key on my fan would start.
So last nite i finally had some time to spend with it and for the life of me i cant get it to stop.I will try the new prom with another copy of the current bin that i have in the car. ( i saved one on a memory stick just in case ) .

Sixshooter...thanks for the tip anything is possible.
WASyl....if i find the problem i will post and hopefully it will help you too
GTA....sean

 

thanks and hope we will find fix for it shortly

regards

 

I second a chaffed wire, thats grounding out the relay, turning the fan on

Do you have a CEL?

good luck with it

-jason

 

CEL you mean SES, no no SES light

best regards

 

Ok, Folks

I thought i better update this....I just tested the car I watched my lappy with TP/RT and was able to verify the fan was running from key on with the lappy showing NO request for the fan. When the car reached the fan on temp, the data showed the request for the fan , so that tells me along with NO SES light that my bin is working properly, NOW where and what do i look for? Where is the relay that controls the fan located? I will have to change it out.....as for poor wires i guess that could happen but the car is very well taken care of no wires have ever been "butchered" they are all covered in their stock covers. So i will start with the simple stuff...can any one show me where the fan relay is located? thanks sean

 

Your relays are located next to the brake booster on the drivers side of the car.

Just because the car isn't butchered, doesn't mean a wire didn't wear through on a piece of metal, grounding the relay, which turns the fan on

You can jiggle the wiring harness by the brake booster and see if that changes the fan operation.

good luck with it

-jason

 

Thanks for the reply,

I see 2 relays behind the brake booster that carry the same part # on them. Would these be the correct ones and is there a way to test a relay to see if it is good? Thanks sean.

 

Hi again,

I just located the relays behind the brake booster, there are 3 of them that all carry the same part # the closest relay to the engine seems to run the primary fan I disconnected it and the fan stopped ....so i switched the relay with another one ( same part # ) and the fan starts again..... so now that i know that the relay is functioning where do i start to look....?? Sean

Mods ...sorry i know that this has "sliped" away from DIY Prom if you wish to move this entire thread to the engine tech board please do...thanks

Edit* I think i found it!! the pass side head has a temp sensor near the rear cylinders I see that the wire has worked loose and has burned on the headers! would a burned /melted temp wire keep my fan on all the time?

 

That's actually a switch, not a sensor. It controls the aux fan (passenger side), not the primary. But yes, when the switch creates a ground at 238* it turns on the fan.

(this is how it works on my '87)

 

Hi again,

I must appologize off the hop, it was my Pass side fan that was on all the time ! I was mistaken and should have made that clear in post #1 . I always thought pass side was primary but i was wrong....DOH..

Any hoo the wire was melted to the header so after i removed it the pass side fan stopped!! The connector just turned to dust in my hand so i will have to get a new sensor along with a new connector....but the bad news is that there is barely any room to put my hand in there I see a long nite with many beer ahead..... thanks to all who gave input to help track this problem down....GTA

 

pass side fan is not pimary one ?? so i have exactly same thing as you do, i'll check that in the morning

best regards

 

WASyl,

I was always under the impression that the pass was primary, but...i was wrong. Good luck with your car, GTA

 

Fix it from underneath the car, it's not hard to reach that way.

Also, if you need to replace the switch I recommend getting AC Delco part # D1855B. It's a lower temp switch that turns the fan on at 210* rather than 238*.

 

80'schild, hi

Thanks for the info, I will consider it when i call my dealer to purchase a new one. I do hope however that i can replace the "bulky" connector that i burnt with something better that will allow more room between the end of the sensor and the headers....GTA

 

Can the actual temp switch in the head go bad? I reused the one from my 305 after using a wire wheel to clean it up and installed it with some arp bolt sealant. It stays on all the time as well. I running ebl so I just re-routed the wire to the ECM so it's controlled there. I got one of the GN 210 sensors and am going to use that for the second fan relay once I convert from a single fan.

But how can a piece of metals conductivity change making the ground contact come on at low temps? Grinding? Thread sealant?

 

I don't know the exact way these switches work, but yes, they can stick on or stick off. In my case mine was stuck on, and it started working normal after changing the switch.