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Where is the Cooling fan motor relay?

Tiny
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  • 1990 LEXUS LS 400
Electrical problem V8 Two Wheel Drive Automatic 170000 miles

1990 Lexus LS 400 that has been running hot, I changed the thermostat but that didn't fix it. While troubleshooting I noticed that the two cooling fans in front of the radiator were not turning on. I turned on the air conditioner and they still didn't turn on. I checked the 30A radiator fan fuse under the hood and its fine. I was told that it is probably an electrical issue and that I should change the fan motor relay. I bought the relay, but I can't find it to save my life. Please help!

P.S. Any other suggestions to my issue if the relay change doesn't fix it. I have no heat and it freezing outside!

Thanks :wink:
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Wednesday, February 6th, 2008 AT 10:48 PM

28 Replies

Tiny
2CARPRO JACK
  • MECHANIC
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Hello,

I have found the locations for you and a test guide so you can confirm the failure.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit.

If the cooling fan is bad this guide will give you an idea of what you are in for when doing the job.

https://www.2carpros.com/articles/replace-electric-fan-motor

I have also found these diagrams to help you see what you will be fixing.

Please let us know what happens.

Cheers
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Thursday, February 7th, 2008 AT 3:48 PM
Tiny
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I uploaded a picture of the compartment I think you are referring to with the top diagram showing. Can you tell me which relay it is? No water in the cooling system? Is that the radiator overflow?


https://www.2carpros.com/forum/automotive_pictures/154609_lexus_engine_2.jpg



P.S. I wired the fans directly to the battery and they worked fine so the motors are good

Thanks
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Thursday, February 7th, 2008 AT 5:16 PM
Tiny
2CARPRO JACK
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The legend on the post above shows which relays are which. Check it out :)
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Thursday, February 7th, 2008 AT 6:01 PM
Tiny
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Yes, I uploaded a new photo


https://www.2carpros.com/forum/automotive_pictures/154609_lexus_relays_1.jpg

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Thursday, February 7th, 2008 AT 6:54 PM
Tiny
2CARPRO JACK
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Is that relay box behindthe drivers headlight. My software says the round relays and 1 square are for the fan, there are 3
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Friday, February 8th, 2008 AT 7:37 AM
Tiny
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Well this power box sits behind the battery which is behind the drivers headlight.


https://www.2carpros.com/forum/automotive_pictures/154609_lexus_relays2_1.jpg



I will remove the battery so that I can get directly behind the headlight and see whats there. I will take more pictures if I need to.

I really appreciate the time you have spent to try and help me. I will keep you posted
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Friday, February 8th, 2008 AT 8:31 AM
Tiny
2CARPRO JACK
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Unbolt it and turn it over so you can find the wires with the same color as the ones that go to the fan
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Friday, February 8th, 2008 AT 5:13 PM
Tiny
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I am sorry for the late update and feedback. I found the relays. The power box was actually located under the drivers headlight and casing. I had to remove all the drivers side lighting units and then the casing. Anyway I replaced all three relays and the fans are still not coming on, even when I turn on the air conditioning. The car is still running hot! Do you have any suggestions.

By the way, you have been very helpful so far. I will definately leave great feedback
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Thursday, February 14th, 2008 AT 2:05 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Okay it seems like you may have a blown head gasket which I have seen cause this problem. Here is a couple guides to help us see whats going on.

https://www.2carpros.com/articles/head-gasket-blown-test

and

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Please let us know what happens.

Cheers, Ken
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Sunday, December 3rd, 2017 AT 6:44 PM
Tiny
CWASH
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  • 1990 LEXUS LS 400
Engine Cooling problem
1990 Lexus LS 400 V8 149, 00 miles

I have recently started having problems with over heating, I haven't noticed any leaks and replaced thermostat after testing it first. After doing so I noticed that my cooling fans wont come on during idle but wille come on during driving. Is this problem simply a relay or could I have more serious problems like a blown head gasket? And what is the best way to determine head problems?
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
MERLIN2021
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https://www.2carpros.com/forum/automotive_pictures/62217_Fans_1.jpg

Check the relays and the fuses, also the water temp switch in the side of the radiator, as for the head, you see any white smoke from the exhuast?


https://www.2carpros.com/forum/automotive_pictures/62217_Fansb_1.jpg



https://www.2carpros.com/forum/automotive_pictures/62217_Fansc_1.jpg

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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
MERLIN2021
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White smoke would indicate a possible head gasket or warped head problem. They are now making products to use in the radiator to seal head gaskets, I don't know how effective they are.
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
AAZAVALA83
  • MEMBER
  • 7 POSTS
  • 1991 LEXUS LS 400
  • 4.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 155,000 MILES
The cooling fans only turn on with the ac being on. I have replaced the temp switch that is in the radiator, and the temp sensor on the intake, along with 3 fan relays. I still cannot get the fans to turn on.
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
FREEMBA
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Check for power on the Yellow/Blue wire at the Water Temperature Switch (located on the left front of engine compartment - on the radiator).

Next make sure that the White/Black wire on the Water Temperature Switch makes a good ground. (Use an ohmmeter. With the Water temperature switch disconnected, connect one ohmmeter lead to the wht/blk wire on the Water Temperature Switch connector and the black ohmmeter lead to the negative battery terminal. The ohmmeter should read "0". If not. Clear the area where the Water temperature switch grounds on the right front fender.)
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
AAZAVALA83
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I checked the ground, it reads 0. I used a probe to test for power pin the yellow wire. No power.
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
AAZAVALA83
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I went back and tested for power with the ignition in the on position. There was power. Where do I go from here?
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
FREEMBA
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Check the IGN fuse (7.5A)
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
MICHAELS321
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  • 1991 LEXUS LS 400
  • 3.2L
  • V8
  • RWD
  • AUTOMATIC
Cooling fans wont turn on, But Fans work and Relays or go.
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
FREEMBA
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Since you have power with the Ignition ON, Ignore my request for you to check IGN fuse (7.5A).

Connect a voltmeter to the ground side of the temperature switch (the WHT/BLK wire) and let the engine run until it reaches the temperature where the fan would normally come on. If the voltmeter reads Battery voltage, then the temp switch is working properly. You'll have to check the cooling fan relays. Easiest way to do this is to switch them with an identical relay (the fuse box usually has more than one identical relay). After the switch, it the fans work, you know that the original relay was faulty.
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)
Tiny
CJ MEDEVAC
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LOOKS LIKE THERE ARE DIFFERENT ONES THAT FIT YOUR RIG (LOOK AT THE CONNECTOR)

SEE THIS LINK

http://shop.advanceautoparts.com/web/PartSearchCmd?storeId=10151&catalogId=10051&pageId=partTypeList&suggestion=&actionSrc=Form&langId=-1&searchTerm=coolant+temperature+switch&vehicleIdSearch=21304&searchedFrom=header

IN THAT "LINE UP", THE "SWITCH" (PLASTIC CONNECTOR) TURNS ON THE FANS, THE OTHER ONE, THE "SENSOR" (WITH THE SPADE CONNECTOR) IS FOR THE IDIOT LIGHT OR GAUGE. (I DON'T KNOW WHY BOTH CAME UP ON MY SEARCH)

ON THE SWITCH, IF YOU GETTER ALL WARMED UP AND RUNNING, THEN REMOVE THE CONNECTOR FROM THE SWITCH BODY, SHORT THE PINS ON THE CONNECTOR WITH A PAPERCLIP/ ETC. (DON'T BEND THE PINS!) YOU SHOULD BE BYPASSING THE SWITCH (AS IF IT WAS "MADE") AND THE FANS SHOULD COME ON COME ON. THIS MIGHT VERIFY WHETHER THE SWITCH IS BAD OR NOT, BEFORE YOU BUY ONE.

IT COULD BE THAT MAYBE YOU KNOCKED THE CONNECTOR OFF, OR THE UNIT JUST WENT ON THE FRITZ.

I RECKON YOU ALREADY LOOKED THE FUSES OVER TOO?

JUST A COUPLE OF IDEAS!

THE MEDIC
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Sunday, December 3rd, 2017 AT 8:58 PM (Merged)

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