'90 auto/ SR /383 /160* thermo /new water pump

Ok so I've finally got my new engine to run. I have got what looks like plenty of coolant in the system. Fire it up and let it run @ ~1200+\- RPM the other day for a bit. After a couple min it starts heating up pretty good and I noticed that the fans didn't come on. So before it got to hot I killed it.

Went to the manual and found out which two wires to jumper together to get the fans to kick on. Well the headlight wiring harness is original to the car and this is what the fans are on, and either the manual is wrong or my car is a fluke because the wires the manual said are incorrect, atleast for my car. I figured out which wires to short together. None the less both fans came on and the harness does not appear to have ever been messed with. So both fans are coming on, the engine temp is obviously hot enough for them to kick on and nothing. I don't have the compressor lines hooked up yet so I can turn the air on to make the fans come on (seems like I read somewhere that will make them turn on). All sensors are new on the engine and plugged in. Custom chip in the ECM from PCMforless and Alvin knew I had a 160* thermo going in.

Could it be anything else other than the relay? They don't look busted/burnt, anyway to test them? Anyway to trick it to make it think the A/C is on so the fans will kick on (if what I 'think' I read is right)? I am assuming that the ECM controls the fans, correct? The interior wiring harness has been taken out and put back in, along with the engine harness replaced with a used unit out of an identical '90. Any suggestions on trouble shooting this is appreciated, I hate having to crank the car and let it warm up to test to see if the fans will come on or not.

 

You might want to check with Alvin because if he didn't reprogram it to turn your fan(s) on earlier then the ECM is still programmed to turn on the fan(s) at the original 228 I believe. BTW, I'm not familiar with the 90 fan system-do you have two main fans or a main fan and an auxilliary fan? I won't get into my thoughts about the 160 thermo-but it has nothing to do with how hot the engine will run. Another thing-remember I don't know 90s, but since you replaced the water pump, and whatever coolant you lost, you may need to burp (remove the air)
from the system. Good Luck.

 

Start the engine and let it idle with AC OFF until it comes up to around 230*. Both fans should be on at this temp. As the car warms up note at what temp the fans each click on. The primery should come on around 210 and the aus at about 223*. If this happens the fans are working correctly.
If the fans are working correctly and the temp continue to raise you either have a bad thermistat (unlikely with new 160*) or there is air in the cooling system. There is a bleed screw on the top of the thermistat housing for letting all of the air out of the system that you will need to open so the air can come out.

 

Both fans on the 1990 are ECM controlled, but those temps sound awfully low for factory settings. At least on earlier years, the A/C triggered the fans, either through the ECM or directly, via the pressure switch. If that is still the method for the '90, the fans won't be triggered by the A/C until the freon is added.


In an L98?

RACE ON!!!

 

There is no bleed screw on the '90 (L98). Its the typical 1st get SBC thermo housing neck. I can turn the fan on by shorting the wires together as stated before and the temp holds steady with the engine running, I just can't get the fans to turn on without manually shorting the wires. There's two fans for this model. Both the same size, one comes on for normal operation, and the other is operated by the A/C as I understand it after reading some in the manual.


***I guess I should also mention that this car sat outside in Michigan in a salvage yard with no hood on it before I rescued it. So the wiring harness and relays were exposed to the elements. Thats why I was wondering if there was anyway to test them before spending money on new ones. According to the manual I either have a bad ground (I checked it its hooked up) or a bad relay. I just want to make sure its the relay and not a problem with the chip/ecm.

 

im with the others about maybe your not letting the car get hot enuf. at one point i had the same problem and would shut the car off when i thought it was to hot befor as it turns out letting the car get hot enuf to turn the fans on. only happened across that cause i got pissed off and just let the car run till it got close to the red and the fan came on. also i have a `90 too as i remember you dont have to jump any wires to make the main fan come on just unplug the two wire temp sensor while the car is running and the ecm will detect the " breach " for lack of a better word and kick the fan on. i think its a fail safe deal. its in the service book. even if you let the car get into the red for a few minutes big deal its not underload or anything i wouldnt worry about that. you might also check back with alvin about the eprom turning the fans on at 160 cause he burned one for me and they came on at 160.

 

HUH!!! you may have a 160 thermostat, and a custom burn-BUT, if your fans are coming on at 160-you've got an unnecessary problem, and it won't belong before you're replacing your fans. Minimum, those fans should come on around 205 and turn off at 185. With your 160 thermo and fans comming on at 160-your engine life is gonna be cut in half.

 

Ok enough with the 160 debate. I think some of you need to go back to elementary and take reading over again. I don't recall in my first post anything about making the fans come on at 160. I bought the 160 because the parts store didn't have a 180 like I wanted in stock. I can't remember exactly its been 6 months since I bought the chip but I think I told him to make them come on at around 190ish.

Thanks to the guys who are trying to help me figure it out though.

My rant.......
What I think is funny is I've read several of the 160 thermo debates and all the guys from up north are the majority of the ones talking about how its bad, and the majority of the guys using them are from down here. If I lived up north (Washington state for example) I wouldn't run one either. But the heat index gets up to 115 here in the summer, and stays there sometimes for weeks, along with the hummidity being abouve 50% all the time. I've had an '86 with cooling issues. It had the stock equipment in it. It would run 220 ish in the summer going down the road. Ok thats not a problem, what is a problem is when it started overheating, I had like 2 seconds in this heat to get the car shut down before red line. Switch to 160 thermo and a manual fan switch which I turned on at 180ish and the car ran, stopped and idling at 195 degrees. And on top of that the car ran smoother with less problems too and I sold it with 215,000 miles on it 4 years later..... Still running.

 

Your post was probably confused when R. lambert read the post above his (steve1ph set-up) talking about his fan coming on at 160.

 

I have just checked the 92 FSM and the temps I posted above are wrong and too low.

PRIMARY FAN

On the 92 LT1 the Primary fan is triggered by the ECM which reads input from the A/C system, coolant Temp Sensor (CTS), Engine Oil Temp Sensot (EOT), Vehicle Speed Sensor (VSS) and RPM.
The ECM will turn the primary cooling fan on when any of the following conditions exist:
ECM sets codes 14, 15, 52, 62.
CTS above 108*C (226*F)
EOT above 109*C (228*F)
AC high preassure switch signal.

Once the primary fan is on it will turn off when the temp drops to 103*C (185*F)

SECONDARY FAN

The ECM will turn on the secondary fan when any of the following exist:
ECM codes 14, 15, 52, or 62 are set
CTS above 112*C (234*F)
EOT above 113*C (235*F)
A/C high preassure signal from HP switch.

Once the ECM turns on the secondary fan it will turn it off when the temp drops to 107*C (193*F)

If the car sat outside without a hood one of the first things I would check are all of the underhood chassis grounds, take them off and clean them just as a precaution.

 

Thanks for this info. I stripped the entire front end to clean and paint the frame rails and then reinstalled the wire harness. I tested with a continuity tester and had connection between the relay ground wire and the frame.

Maybe I'm just not letting it get hot enough, but the temp guage inside the car got awful close to 260 the other day. Wish I had the digital guage like I had in my '86 so I could tell exactly what it was. Like I said when I forced the fans to come on the temp guage sat right in the middle, which is where I "thought" it should be, but I've never owned a '90+ vette with these kind of guages.

 

The 90 should have a digital guage as well on the dash. Just push the Guage info buttin in the DIC and you should be able to cycle through Volts, Oil Temp and Coolant Temp.
As the senders for the digital guage is what the ECM reads it is better to use these for checking the temp for fan functions on a 90+ vette.

 

Great thanks, I didn't know it had that function, I'm still learning the inside of this car.

 

Dude-my second response was meant to clear up a post by steve1, don't believe his fans come on at 160, and didn't want you to think yours should. I could say alot about you know what-but I didn't and won't. Was just trying to help with your problem. your fans stock
are supposed to come on in the 220-230 range, as Jerris said-and I believe my first post did.

 

Also. Heat index, PHOOEY. Humidity, PHOOEY. Not a factor in cooling a car engine.

RACE ON!!!

 

 

Maybe I'm Barking up the wrong tree, but I, too live in swampy La.My '96 Lt 1 was showing as high as 260 degrees.I changed out the temperature sensing unit and now it reads in the 228-230 range,even at a red light in summer.

 

You post that you have a 90, which was L-98. My 88 L-98 factory stock specs are 108*C (226*F) for the main fan to come on, and 109*C (228*F) for the aux. fan. Since jerris posted that the 92 LT1 main fan comes on at 108*C (226*F) the same as my L-98, I would assume that your L-98 fan should kick on at the same temp. According to jerris the 92 LT1 aux fan comes on at CTS above 112*C (234*F) which is 6* above that of my L-98, so you should certainly see your aux fan kick in between 228*F ~ 234*F. Perhaps you sut down prior to this point?

The GM Parts & Illustration guide shows (2) relays for the fans on the 90 Vette, both GM part #14089936. You should be able to swap the relays to test them. It is not real likely, but still possible that they both have failed due to exposure to the environment or other causes, so you might consider buying a new KNOWN GOOD replacement from NAPA for about $11. Use this known good component to test both existing relays. If you find that you have one that has gone bad you already have the replacement in hand. Otherwise consider it a cheap relay test tool.

You say the car's wiring is stock as far as you know, but it does not match the schematic in the manual. Are you using a Factory Shop Manual or a knock-off version? The discrepency might be important is resolving your problem.

 

Just got through with a cooling fan problem-on my 87 the aux. fan was comming on, but not the main fan. In my case it was the fusible link had blown-the red wire from the power tower (behind the battery
where several red wires connect) to the relay. Cured my problem. IF your 90 is like an 87, you should be able to unplug the main fan relay, you should be able to read A,B,C,E ect.
on the relay connection, check the red wire with a test light-it should always be hot-if it is, jump the red wire to the black and red wire-if the fan runs-you've got a bad relay-if you find no light to the red wire
you've got a blown fusible link-make sure you check the fan fuse though. OH, please don't take offense-but-if you're running a 160 thermo, and your fans have been programmed to come on early- you may be taxing the fuse-meaning the fans are almost continusally running.

 

The 90 has the new analog/digital gauges. Speed and fuel are the only digital gauges left.

I had a problem recently on my car with the HVAC system. The freon was low and kept setting a code 09 in the HVAC for low freon. Whenever that codse was present my fans would not work even with the A/C on.