Question about 2003 Chevrolet TrailBlazer

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Engine fan speed stuck on high. How do I fix it?

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Hi, it seams that your (thernostat switch) has remaind CLOSED meaning the thermostat switch normally in the radiator (near the bottom) or in the top of engine needs replacing. these stats normally go OPEN CIRCUIT hence NO FAN. there are 2 thermostats one used for fan 2 wire the other 1 wire for temperature gage. i hope this is useful gerry

Posted on Sep 09, 2010

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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

1 Answer

My car 2008 Chevy Uplander warning light came on stating A/C shut off for engine protection. My question exactly as 1posted 2011. Gauge not Reading. Fan running continuously. Doesn't seem hot.


What gauge not reading , Temperature ? you posted back in 2011 ? You did feel you should take it to the repair shop ? You need to take this to a ASE certified repair facility ! This is a complex electronically controlled cooling system , Three relay's controlled by the ECM -engine control module turn the fans on in two different speeds ! There could be DTC'S diagnostic trouble codes stored in the ECM, HVAC module , BCM !
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the low speed fan relay, which is the Fan 1 Relay. Voltage is applied directly to the left cooling fan through the switch side of the low speed fan relay. The right fan is connected in series to the left fan through the de-energized Series/Parallel relay, which is Fan 2 Relay, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the Series/Parallel relay, and the high speed fan relay, which is the Fan 3 Relay. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed fan relay and ground through the Series/Parallel relay.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.
One of the relays could be stuck on ! An for the gauge you have to have it removed an fixed , there is a stepper motor behind the gauge needle an they go bad ! Or replace the instrument cluster !

May 14, 2015 | Cars & Trucks

3 Answers

How do i fix the blower stuck on high


if it only goes on high, the resistor needs to be changed . It is on firewall ,passenger side of car under wiper assembly behind alternator. not a hard job to do, part is not expensive. you will get low,med , and high back. if not switch on dash panel, or change blower motor, last ,since it is going on- working. good luck

Feb 22, 2015 | 2003 Chrysler Town & Country

1 Answer

1996 ford tbird fan runs at high speed once engine is started.


Have you tried changing the fan relays? Sounds like they may be stuck on.

Mar 11, 2014 | Ford Cars & Trucks

1 Answer

How do I fix the blower fan in my Ford F-150? It's STUCK on HIGH!


the problem is not the fan (blower motor) , it is the resistor in the blower motor hosing under the hood...
open the hood and look over by the passangers side firewall to locate the blower plenum (housing).
There is a plug that has 4 wires and it is plugged dirrectly to the housing.behind that is the resistor configuration that runs the fan at the different speeds ( more resistance = slower fan speed).
It is this part you need to replace.

Mar 23, 2013 | Cars & Trucks

2 Answers

Overheats unless ac is running


The thermostat may be stuck. If it dosent open then the engine will overheat. If you turn the ac on then the air rushing around the engine will help cool it down. Replace the thermostat and it should fix it

Dec 30, 2012 | 2008 Pontiac Grand Prix

1 Answer

I have a 02 trailblazer that service engine light came on code for high speed fan came up now truck has a lot better pick up when you push the gas


the fan control module has the fan stuck on high speed. the reason for the extra power is because the ECM is adding fuel to the injectors due to the engine running cooler than normal.may want to get the cooling fan replaced it comes with a new control module.

Aug 08, 2011 | 2002 Chevrolet TrailBlazer

1 Answer

My car is running hot, and I dont know what to do.


{: ) You didn't mention the model of your vehicle. Anyway, we can try some cooling system basics.
You can begin checking with the things that keep the engine cool.
1. The coolant. Are you using plain H2O? Check the coolant level and also look for signs of coolant leaks.
2. The radiator. Check for obstructions at the radiator area like plastics and debris. Foreign materials could have accumulated on the radiator fins. Clean if necessary.
3. Cooling fans. Check for damages or cracks. Is it operating at expected speeds when it should be? For example, at 106deg it works on low speed, at 110deg it should spin high speed. If it stays on low speed all time or none at all, check the fan relays and fuses.
4. Water pump. Is it noisy? Have you checked the belt? It may be old and cracked, better replace it. If a thermostat is stuck, coolant won't circulate and engine will heat up fast to undesirable levels.

How about the other things that add more heat to the engine?
1. Engine pulleys getting stuck. A/C, water pump, steering pump, alternator, idler and tensioner pulleys.
2. A/C system high pressures on the condenser.
3. Oil level and pressure low
4. Poor engine emissions performance. Engine timing, tune-up, clogged exhaust pipes
5. Stuck brakes or bearings
6. High ambient temperatures
7. Poor wheel alignment, low tire pressures

I hope I didn't miss out on any other more important things to include. Wish you goodluck.

Jul 24, 2011 | Buick LeSabre Cars & Trucks

2 Answers

Ford F150 A/c


could be a stuck fan relay near the blower inside the engine compartment.

check the fan relay for a stuck contact..

tnx 4 using fixya.

drcool

Aug 07, 2008 | 2005 Ford F-150

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