I have a 91 z28 5.7 stock motor. Recently just replaced ecm due to the old one failed. After I installed new ecm I have noticed the fan will not stay on. When at high temp (230+) it starts but then stop intermittently. I have replaced relay on driver side firewall verified the fan works with direct power. Any suggestions to my next possible remedy? Thx for any help

 

Check fan switch on passenger side cylinder head there known to go bad over time also check connection.

 

Okay will do thanks

 

Do you happen to know a good brand to buy and do they have ones that might turn fan on sooner then oe specs?

 

I know hypertech sells one that makes the fan come on sooner also do a search on here and people have commented on other companys as well.

 

thx

 

I think that part was discontinued. Which sux.

 

Well replaced the fan switch on the passenger side if the block. The old one had Teflon tape on it. Installed new one without the Teflon tape this time. Also went ahead and replaced thermostat with a 180° since I had one. Previously the ecm went bad and main reason why I parked the car...after the re manufactured install that's when I started having issues with the cooling fan. So I returned the ecm and purchased another from Napa auto. Going to install this one this evening and see if the fan issue is fixed. Hopefully it does. Question now is I wanna make sure the temp gauge is coerce so I will purchase a temp gun on the way home but would like to know is the sensor on the driver side for the factory temp gauge? Thx for all the help....better then paying a dealer service bill

 

Well after all that even another reman ecm temp gauge sensor new fan switch new relays new Stat....no cooling fan
Rrrrrrrrr. Driving me crazy. So I went ahead and used ac switch and connected two fans together via dash ac switch....

 

Have you tested the fan motors? You noted in you first post that the fan does comes on at 240, which fan is it? Primary or secondary (ac fan)?
Is your prom and fan switch stock? Have you checked the wiring leading up to the fan switch for any burns, cuts?

Lets see if we can figure out the issue.

 

Started running shitty due to bad ecm. Replaced with reman ecm twice now. Replaced temp fan switch(passenger side between 6&8 plugs and didn't use teflon tape since it is a ground circuit), tstat 180°, replaced sensor for factory temp gauge (driver side block mounted), replaced fan relay(driver side firewall under hood), flushed and purged coolant system, ran straight 12volt power to cooling fan to make sure fan motor was good, no check engine light but have not checked for codes yet.The ac (primary fan) does engage correctly. I have removed wire looms to check for faulty wires and all check out good. Keep in mind the car only has 67,000 original miles and garage kept real clean. For now I have both fans working with dash ac switch with compressor power disconnected. Anything else I can check to get this coolant fan to work correctly?

 

I too am having the same issue with my 91 Z 350. Replaced every temp sensor/sender.

-Gauge pegs before any fan comes on
-TunerproRT shows fan finally coming on when coolant temp is 110.
-New ecm

 

I ended up ordering a Jegs 175 coolant fan switch (passenger side block) and put in a 180° thermostat failsafe. Using a infrared temp gauge on thermostat housing fan now comes on at 176°. Car was cooling great til it decided to throw a rod. Only 66,000 miles on it. Sorry off subject.
Try the Jegs fan switch. Ordered mine from summit. Hope that helps

 

ignore.......signature not working

 

Thanks, but I'd rather getting everything working as it did from the factory. Mine will work, just gotta figure it out. Sorry about your engine loss....at least your mind is off your cooling problem.

Please get it working. I've referenced it in the past. It's a very valuable source of info. Thanks for putting it out there.

 

haps ,
I just have to ask, why keep the car running at 220* and higher temperatures ?

Side note = Just for future reference, never run two fans on one circuit. Especially a stock one.
The gage wire that is being used is not heavy enough to carry the load.

When the fuse blows or worse the wires fry you will find yourself pegged out in the red zone and the coolant will be boiling in the overflow tank.
Not a good situation to be in.

I'm suggesting running two fans, each on their own independent circuit. One fan acting as backup for the other.

 

Simple. It worked just fine from the factory and that's the way it was designed. Can it be improved? Sure, but there's just no need. I command a better than average ability to understand a vehicle's 12 volt system and could easily hack up the harness and solve the problem. Besides, finding the problem within the confines of the stock configuration is sometimes much more difficult, and for me, more entertaining. I'll admit, this one is a head-scratcher.

 

Sorry,
I did not mean you specifically concerning the circuit. I should have been more clear .
There are many here with similar problems and was simply speeking in genral.

As far as the running temps go, lowering them is a modification that is very common with our cars here so was just queraus about it ......

Thats great about your outomotive electoral experience and nolige concerning it.

Even though its simple for some, it took me awhile to grasp it all.

Again sorry,

Ron

 

No apology necessary, legit question. Happy 239th B-day to the Marines btw.