chevyboy07 91

both fans are "dead" in my 92. Fuse under dash is good. Link on fender well lip (red/org wire) is good....what does that control anyway?

I have searched and seen a lot of conflicted info on wire colors and what does what. I chased the wires from the fan motors all the way back towards the firewall of the car and the disappear into the main harness and thats it......

Chiltons manual was no help either

Anyone have an "on car" pick of where these relays are?? Again, conflicting info is out there, probably b/c of year differences...

thanks!!!

yevgenievich

iTrader: (4)

this is old post but anyway. I have same problem, there are 4 identical relays under the hood, two by the firewall on driver side and two by the air filter. I have 89 t/a. It seems like most of the people point out that the fan realy is on the firewall.And the second one in there is the fuel pump. I unpluged what should be a fuel pump relay and started the car up, i've let it run for about a minute with no shortage of fuel evident, and being a 15 mpg car i am sure it would've suced all the gas out of lines by that time. So i am not sure which relayes do what anymore. All i know is the fans will not turn on no matter what i do until i puled them out and ran wire directly from battery. Now i read about temp switch that according to some people is in the passenger head or according to others is in the block where it is not seen from top. I am not sure if the temp switch being bad would've stoped the fan from turning on when i turn the ac on. So my question is which relay controls the fan and how do i make it to turn on atleast at 225*. I tried swaping out the relays and it did not seem to help.Last time i set in traffic for one minute the temp whent up to 245* or so. btw, my budget is about $25 thnx
EDIT: don't know if this helps, but i just found what looks like a ground wire that should go to the block but just hangs in there. It is on the firewall on the passenger side of the motor. Any dea on where it goes and if it could've coused no fans situation

jimdutro

iTrader: (1)

Don`t know about a `92 but my `88 Iroc dual fan has one relay on the radiator support and the other is on the passenger side fender.

jimdutro

iTrader: (1)

Look between #7 & #8 cylinder on the passenger side. That might be your fan switch and that is what the wire goes to. If it is a single wire, ground it and the fan should come on. If it works, attach it to your fan switch. Other mods can be done later to cool it down more. Send another reply to this post if you need more info.

yevgenievich

iTrader: (4)

i remember that wire because it's been melted by headers and i had to reconect it. It's too late to check it now, but maybe that ground wire that is not conected that i found lets the head to be grounded, and because it's disconected that wire(to temp sensor) never gets ground. Now you saying that the realys by air box are the fan relays. I thought that they are but then i found two identical ones on the firewal and read on one of the posts that the fan relay is on the firewall. I will try grounding that wire that goes to the head and see if it does anything.thanks for the info

yevgenievich

iTrader: (4)

i tried grounding that wire, and i could hear something clicking or spaking but niether of the fans would turn on. i tried switching elays, and actually was able to try a new one, but it didn't do anyting. what else could be the problem?
, btw which fuse under the dash is for the fans? i looked there and pulled few out that seem like would do something to the fans and they were good

IROCU2

yevgenievich,

I had the same problem and here is what I did. I tap on the fan motors with a wrench and they came on. So I know that they work and I have to replace them. Try that and see if they come on.

yevgenievich

iTrader: (4)

hiting the fans doesn't turn them on, so far the only way i was able to turn them on is to hook them up to the battery. For some odd reason the don't get power.

yevgenievich

iTrader: (4)

anybody knows where the fusable link is located at? maybe it is messed up so fans don't get any power

jaredi

To find which is the fuel pump relay by unplugging them you'll first need to disconnect the oil pressure switch by the distributor. That circuit keeps the fuel pump energized as long as the engine has oil pressure just in case the FP relay were to fail in traffic or some other situation where a power loss would be potentially dangerous.

yevgenievich

iTrader: (4)

that makes sense... i took out all the relays that i could find and the car started up fine a drove around for 5 minutes. but i think i am sure now that two relays that i am looking for at are by the passenger fender and now i know that fusible link is somewhere near the starter so i just have to find it. I don't have the money to buy a jack to get under the car which is one of the things that been stopping me from working on the car so far.

l_dis_travlr

The dual fan set-ups have dual relays, with separate control circuits.
(Usually one from the ECM, the other from the infamous switch prone
to wire/connection melting, located in the passenger side head.)
What they share in common is a constant input directly from the
battery, via either the power block connector or at the starter.

Identify the wire colors in the fan connectors, & look for relays
with the same color wires in the connector plug. These are probably
pretty heavy gauage, minimum 12. When you find these relays,
another wire in the connector should be red or orange, probably
larger at 10 gauge. Test this for constant 12 volts, if not then
there is probably a bad fusable link at the other end.

Personal experience...
As fans degrade, they will continue to run, but not as effectively,
and will draw excessive current, possibly the reason for fusible
link failure.

Good luck,
kk

naf

iTrader: (7)

In order to verify definitively the correct relay for the fan(s) perform a continuity check between the fan power wire (from fan motor) and the relay output and/or the temp switch wire and the relay control wire. Just make sure you're not inadvertently checking ground to ground.

theimpaler68

iTrader: (1)

ok here it goes and i hope this helps everyones questions because i have already fiddled with everything you guys are having problems with...
first the fan relays on my t/a were the 2 under the air box . second the wire by the block should be the one that goes to the secondary fan switch... i believe mine is green and white but to check this... if the car is off and i would hope that if you are in the engine bay then it would be... you need to touch the wire to a power source like the starter... if that is the wire then the fans will both come on. i have a plug in my engine block that needs special tools to remove in order to install a fan switch so that i can plug in that wire to ground it. because in order for the fans to kick on with the car running and off with the car off... then that wire must be grounded. i ran more wire into the cab of the car to a toggle switch and ran the second wire to a ground. this way you can turn the fans on when you want. i do recommend a 180* stat because your car then should not get any hotter than 200* when the stat is fully open. i hope that this shed some sort of light on the situation

yevgenievich

iTrader: (4)

are you saying that i should replace the fans anyway?

l_dis_travlr

Good question, which I readily admit to not having a good answer.
I'll share the exact experience. Life started out w/ a tired single-fan
TBI, 305. After an incident or two of overheating in stop-n-go traffic
here in Houston, we found the relay in-operative, and replaced it.
This lasted a short while, and the symptoms returned. Being a bit
more thorough this time, we noticed the charring on the relay
connector base, on the power-to-fan cavity. Not rocket science
to figure out that current draw is to high. Since (at the time), this
was my son's car, his solution was to just by-pass the relay with
a switch, into the cabin. He subsequently gave-up the car to me,
whence began a total restoration, which will include a significant cooling
system upgrade. I was never able to determine exactly HOW to
verify the fan motor. Measuring large DC current (10+ amps) is do-able,
but not easy. And even then, I couldn't find what should be acceptable
current draw. If you find a bad fusible link for the fan power, but no
dead-shorts, I'd seriously consider trying to find another motor. At worst
you can then try a side by side comparison. I hope this helps, without
being overwhelming.

kk


PS -- yevgen, check your PM.

yevgenievich

iTrader: (4)

i found out that the orange wire that goes to the relay has no power while it should. So know all i have to do is figure out where it goes and fix it.

naf

iTrader: (7)

Should go through a fusible link to either the positive battery post or the positive lug on the starter. Fusible link may be shot, high current could have killed it. (I'm not saying it did...)

Replacement fan motor is like $20-25 at the parts places. You can shop around on-line for the best price.

yevgenievich

iTrader: (4)

i found fusible link to be melted, i replaced it with 20 amp fuse. Now i get power in the orange wire; however the fans still would not turn on. I already drained my battery trying to mess with it and have to use my stealth with a set of jumper cables just to get the bird started. I found out that when using a test light when i poke trough the gray wire the fan will turn on. The fan will not turn on when i turn the ac on, but i don't want to turn the ac on any more because the ac compressor starts to make loud ticking/knocking noise when turned on. If i put the car in diagnostic mode it should turn the fans on, right? Anyway i was thinking coolant temp switch but if the gage is showing the temperature then the coolant sensor should be fine, am i correct? it is dual fan setup

naf

iTrader: (7)

A 20 amp fuse may not be large enough for the start up load, unless it's a slow burn. That's why a fusible link was used (at least with single fans, which may have a larger motor).

The A/C switch for fan operation is pressure controlled on later models. If your A/C system is not generating adequate coolant pressures it may not close.

Guage temp sender is separate from the coolant temp switch, completely separate and not connected.

Try grounding the lead that connects to the temp switch on the passenger side head. With the engine in Run, touching this lead to a ground (engine block/head is fine) should engage the relay. This may be the lead at the relay that you're grounding with the test lamp somehow to engage the fan.

yevgenievich

iTrader: (4)

i've put the car in diognostic mode the other day and the fans turned on. As for a/c there is a leak where there are two pipes come into the a/c compressor and when i turn it on it is real loud but blows cool air. I will try to put everything together and drive the car in traffic to see if the fans ever turn on. Should i go ahead and replace the coolant temp sensor on the front of the manifold? Also i tried grounding out the switch on the passenger head and it didn't do anything, but that was before i put a fuse in and now the secondary fan is in the trunk