Question about 1999 GMC Sierra

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The fan control only work on 1 and 2 3 and 4 dont work at all

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Hello, what we have here is a malfunctioning blower resister module located under the passenger side of the dash.Also when you take off the connector check it over good ,sometimes the terminal ends get burnt up.The part runs about $35 :)

Posted on Sep 07, 2009

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FANS WONT COME ON ,,ALL FUSES,RELAYS AND ELECTRIC FAN MOTORS ARE NEW,,THERMOSTAT IS GOOD,,WHERE IS ELECTRIC FAN TEMP SENSOR LOCATION


op
why not post symptoms first and not a barrage of parts.
must we decode that to a symptom,. kinda hard right.

I will not guess. what is wrong, nor what is not working on your car. now what fans you are talking about, up to 4 fans on cars.

cab blower fan (wild guess blower is ok) and so is HVAC, ?
radiator fans
Condenser fan.

my wild guess to , engine over heats?????????
if yes, the scan it first. no not last FIRST.
it dont work like you think its not a 1988 Samurai.
sorry,
on modern cars, they got smarter, the engine goes
gee the PCM knows water temp why have a fan temp regulator.
hark , now it dont. (saves cash on useless parts)
but has a relay , (well until you have my car and the relay is now 100% electronic, called a huge transistor)
we've used this tech in industry for years, but car makers just learning how still.
i digress. but evolution and history helps diagnosis.
what is there?

Ill look for you, ive posted this 100s of times
the book is 4 bucks to see online. the real deal
lets look now.
XL-7 (the dash matters big time)
answering for , overheats engine, and fans on RAD dead.
(some are staged, PCM brains... now. and also chain ops based on if A/C is on or not) facts.
first I see 2 fans... ok.
the next page shows nice block diagram of the fan system
yup, NOT Simple.

ill post those words for you.
"The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.
During low speed operation, the ECM supplies the ground path for the low speed cooling fan relay which is fan 1 relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the series/parallel relay which is fan 2 relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The ECM grounds the high speed fan relay, which is fan 3 relay, and the series/parallel relay, which is fan 2 relay through the high speed cooling fan relay control circuit. This energizes the series/parallel relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse 1 on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 16 km/h (10 mph). This is to prevent a fan from cycling ON and OFF excessively at idle.
end quote.

i bet you didnt scan it , like 99.9 % of all posters here dont.
DTC Descriptors
DTC P0480: Cooling Fan Relay 1 Control Circuit
DTC P0481: Cooling Fan Relay 2 Control Circuit
DTC P0691: Cooling Fan Relay 1 Control Circuit Low Voltage
DTC P0692: Cooling Fan Relay 1 Control Circuit High Voltage
DTC P0693: Cooling Fan Relay 2 Control Circuit Low Voltage
DTC P0694: Cooling Fan Relay 2 Control Circuit High Voltage
Diagnostic Fault Information

is the ECT showing overheat, yes no?
if yes, it must operate a fan or 2.
the book even covers all tests for fans dead, in a large truth table.
both the FSM and alldata.com have that, its no secret ,its published in 4 major places.

lets back up
if the engine coolant is low (no that side tank the engine and rad)
the ECT will lie. if that happens the fans may not come one
that is because the ECT is useless measuring air, for water.
that water must touch ECT for ECT to work.
this is FIRST
then scan the ECT does it show overheating, IT must if it IS overheating. fix that next if it lies to you,(IR gun in hand)

The system has staged fans.
i cant find the trip points in my crappyy online pages.
but is like 225f then 250f trips. is my guess...
about. if the engine over heats, check fuses first then scan it.
it will simply tell you why its bad.
eg, fan1 output dead.
or if you hot wire a fan and its dead, then it is.
(only on cars with non modulated fans,,hot wire them,else not.)

now the link to the 4 buck real book.
the non dash XL7 (my guess) you this pick yourself... cant see car.
https://suzukipitstopplus.com/Products/10182-2007-xl7-service-manual.aspx

this is how it really works
the ECU has software that decide trip points for fans.
hard coded, this is. based on how hot it is and if A/C is on not.
its way smarter than 1988 and better.
the DTC errors can see an open line, shorted to ground or stuck 12v.(runs all time error)
(tells you relay is good or not)

25839272-0kjd5huq4lpr130nt243wle5-3-0.jpg no scanner no joy , sorry, tis a fact.....

25839272-0kjd5huq4lpr130nt243wle5-3-2.jpg

Aug 27, 2015 | 2007 Suzuki XL-7

2 Answers

I have a 2004 dodge Durango. one day the interior fan control stopped working...you have to turn it to 3 to get the fan to cone on..?


Recommend replacing blower resistor card, get a factory one the aftermarket ones dont seem to last as long

Apr 13, 2015 | 2004 Dodge Durango

1 Answer

1999 Jeep Grand Cherokee Laredo 4.0 We have replaced fan assembly and the relay. the fan is still not coming on???


computer control may not be working have it checked with scan tool actavate the fan relay if it dont work either controller or wires

Sep 07, 2013 | 1999 Jeep Grand Cherokee

1 Answer

Blower fan doesnt work 1 through 3 but on speeds 4 and 5 it does is that the resistor tot he blower fan if it is how do you take it out


There is a voltage control ballast which controls the different speeds. This is usually located in the airflow from the fan to keep it cool, and is about $15. Usually one speed still work if this goes out. High should work. [Look under the dash of passenger side in the air flow ducting, maybe behind the glove box. Look for a connector block with 3-4 wires comming out, held in by 2-3 screws. Dont run it outside the air flow, it may burn out real quick.]
If this is helpful - Please vote

Jul 25, 2011 | Chevrolet Malibu Cars & Trucks

2 Answers

Diagnostic code for my 2007 saturn ion says p0480 cooling fan 1 control circuit malfunction. what does this mean.


WHAT IT MEANS YOUR FAN CONTROL RELAY CONTROL CIRCUIT IS OPEN OR SHORTED TO GROUND. FAN CONTROL RELAY CONTROL CIRCUIT IS SHORTED TO SYSTEM POWER. THE FAN CONTROL RELAY POWER CIRCUIT IS OPEN CHECK COOL FAN 1 FUSE. FAN CONTROL RELAY IS DAMAGED OR HAS FAILED. PCM HAS FAILED.I LISTED ALL POSSIBLE CAUSES TO CODE PO480.

Jul 05, 2011 | Saturn Ion Cars & Trucks

1 Answer

On my 1999 ford contour fan wont turn on.hot wired it and it works.my temperature gauge in control panel on all the way over.i dont know if the relays are good or not. dont know where if the temperature...


1. Check the fuse to the fan
2. Have a look at https://www.youtube.com/watch?v=ELg0H5Dr014 and replace the sensor.

(I'm not sure what the problem is with the ac/heater: I understand that the blower worked but, for some reason you replaced the resistor, and now it doesn't...)

Aug 08, 2017 | Ford Contour Cars & Trucks

1 Answer

My 2002 tahoe a/c compressor runs when you dont a/c button is off


A/C clutch might be stuck on, on the compressor itself

Mar 19, 2010 | 2002 Chevrolet Tahoe

1 Answer

My car fan dont turn on when ac is off


Check the operation of the radiator cooling fan circuit:-
1) check fan control temperature sensor is ok,
2) check/replace the cooling fan control relay,
3) check supply fuse for cooling fan is ok.

Oct 01, 2009 | Hyundai Motor 2002 Elantra

1 Answer

Fan control dont work on 1 and 2 position 3 and 4 are ok


u need to check ur switch and after that if the blower is controlled by a resistor or not , if so have it check if the resistor is "open" or not

hope this helps
have fun

Sep 25, 2009 | 2004 Chrysler Sebring

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