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#1
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GM 3.1 Engine Cooling Fans inoperable
95 Chevy Lumina w/3.1 overheating. Engine cooling fans are not coming
on, regardless the temperature, or whether the A/C is turned on or not, (am assuming that at least one of the engine cooling fans should turn on when the A/C is activated.) What are the related fuses and or relays and their locations? What is the circuit description for these fans? TKS, Jim |
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#2
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I glanced at a diagram for this info because I couldn't remember any
specifics. First, the ECM controls both fans independently, and each fan has its own 60a maxi fuse and relay. Both fans are wired to ground at the "lower left front of engine" according to diagram. All of the related fuses, fan relays and A/C clutch relay are in the big fuse box under the hood, I think near the wiper motor. I don't know that the ECM would turn on the fan(s) with the A/C on -- assuming cold weather - the cycling pressure switch input would tell the ECM to keep the A/C system off. Check the maxi fuses first. Then I would unplug the fans and power them right to the battery to see if either is bad. Also make sure the large black ground wires going to each fan are OK. {[Additional step to verify ground integrity: you could temporarily wire a large load like a spare headlight to batt positive and ground it at the black wire. If light turns on then go further and check voltage drop on the ground side with a DVOM. Look for less than 0.25 volts.]} Still no luck? The ECM uses coolant temp (ECT) input to turn on the fans. Find the two wire ECT connector and backprobe the yellow wire with the engine hot and running. You should see about 0.5 volts hot. Less if its overheating. If the voltage is high there suspect a bad ECT sensor or a lifted ground (the black wire). You can also check / jump the fan relays with all system components reinstalled - given you know the fans, grounds, and fuses are ok. You can jump the large wire terminals Red - Blue on one, Red to White on the other, and pass direct power to the individual fans. Or you can backprobe the ECM signal wires with ground with the relays installed. (Loosen the relay block and work from the underside) These wires are Green/White for one, and Green for the other relay. This will simulate the ECM trying to turn on the relays. With all of this info you should be able to trace down the defective component or wire. Toyota MDT in MO |
#3
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Thanks for the very detailed circuit descrtiption and troubleshooting
ideas. I'm lost without my AllData (local library closed holidays.) Am really ap- preciative for sharing your "Black Belt" technique's. Am going to have a litlle morning coffee, then brave the cold to go troubleshoot. Will let u know either way. Thanks again. Jim P.S. How did u come about the name Comboverfish, and are u a manager in a toyota div.? |
#4
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> P.S. How did u come about the name Comboverfish, and are u a manager
in > a toyota div.? Its such an obscure quote from a show no longer on TV that noone watched it seems pointless to explain : ) If anyone ever gets it I'll know they're a fan and thats a more fun prospect. I'm a dealer mechanic. Good luck with your Lumina. Toyota MDT in MO |
#5
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There are two ecu's (fuse boxes) under the hood. Which one contains the
wiring to jump the fans. Ecu #1 is on RH front, and Ecu #2 is on LH front. Also, that ECT sensor, is located where it looks as tho the air duct assembly, containing the at least the TPS among other assemblies, will have to be removed from the intake manifold in order to get to the ECT.It looks fairly simple to take off by simply loosening a couple c-clamps, although I don't have any experience with removing this assy, is there any precautions that one might take in order not to disturb the adjustments on these assy's. TKS Jim |
#6
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gobroncos wrote: > There are two ecu's (fuse boxes) under the hood. Which one contains the > wiring to jump the fans. Ecu #1 is on RH front, and Ecu #2 is on LH > front. > Also, that ECT sensor, is located where it looks as tho the air duct > assembly, containing the at least the TPS among other assemblies, will > have to be removed from the intake manifold in order to get to the > ECT.It looks fairly simple to take off by simply loosening a couple > c-clamps, although I don't have any experience with removing this assy, > is there any precautions that one might take in order not to disturb > the adjustments on these assy's. TKS Jim Please don't take this the wrong way, but you may be in over your head here. I'm simply basing this from your terminology and observations. I fear that it's going to be difficult to guide you any further if I need to go over all of the basics. I'll try to address this post, though. A fuse box is different than an ECU (ECM). The fuse box I'm talking about has a bunch of relays and big fuses in it and should probably have a black plastic cover on it. The cover should have drawings and labels for all of the fuses in it. So should your owner's manual incase the cover is missing. Atleast find this box, locate the cooling fan relays and the two cooling fan 60a Maxi fuses. That's where your problem is likely to be. But you still should power the fans as described before to make sure they work. The ECT sensor has a small brass body and a black plastic connector. It threads into a water outlet or into one of the cylinder heads, probably near the internal "V" of where the two heads meet. I don't have a 3.1 GM around and can't remember exactly. It will have both a yellow and a black wire going to it. Test this as previously described. That's all the ECM uses to turn on fans when the engine gets too hot, so the ECT sensor or its wiring circuit or the ECM are all possible causes of your problem. The TPS is not in any "ductwork", its attached to your throttlebody, which I'm sure doesn't need to be removed to test the ECT sensor. You may need to remove the intake boot and aircleaner assly if it helps you get a test probe to the wiring. You won't be able to keep the engine running with the snorkle though if there's no air going through the MAF sensor. So get the engine really good and hot, shut it off, and procede with ECT sensor test. Toyota MDT in MO |
#7
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No offense taken at all. I really appreciate the help.
I'm completely w/you as far as the terminology goes and have been able to successfully jump the fans from underneath the ECU #1 as u explained. Still having a problem accessing the wiring coming out of the ect sensor to measure the voltage. The wiring comes directly out of the sensor then under the intake manifold and from there I lose it. Still not able to access either the sensor or it's wires enough to get the probes on it to measure the voltage. Once again, thank-you for your time. Jim |
#8
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If you jumped the big wires at each relay and the fans turned on then
you may have a bad relay(s). You atleast know the high current wiring is sound enough to run the fans. Your _biggest_ concern right now is "why won't my #1 fan come on when my temperature gauge is in the red?" The ECM should close the #1 relay when it sees about 220 degrees F coolant. You know the wiring and both fans are adequate. --- So --- you could swap the two fan relays to see if the #1 relay is bad. If the unused #2 relay is good and the #1 is bad (and that's your only problem) then the #1 fan should come on with a HOT engine. Another thought, some GMs will turn on the fan(s) when you simply unplug the ECT, but if you jumper the yellow and black wires together it will surely command the fans on. You could test the command ground signal to the relays this way without overheating the engine. But you need to clear the resulting trouble codes when you're done. (Pull the battery negative cable for ~ 20 seconds is the quickest way) Toyota MDT in MO |
#9
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Just returned from the salvage yard. I was able to use this car in the
junkyard as a "cadaver", and did some exploring. I managed to obtain an ECT sensor and some more relays taken out of the same positon as in my car (however they appear to have a different part # written on them), nonetheless, they both have the same color wires as mine did when i jumped the fans( beneath the ECU). I'll first swap the #1 relay w/the #2 relay (their part #'s are the same,) and I'll get a voltage reading before and after it heats up. I'll get back in a few. TKS Jim |
#10
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"Comboverfish" > wrote in message oups.com... > > P.S. How did u come about the name Comboverfish, and are u a manager > in > > a toyota div.? > > Its such an obscure quote from a show no longer on TV that noone > watched it seems pointless to explain : ) If anyone ever gets it I'll > know they're a fan and thats a more fun prospect. > I'm a dealer mechanic. > > Good luck with your Lumina. > > Toyota MDT in MO > > Sounds like "Red Dwarf" or "Hitchhikers guide TTG" type stuff. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
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