dc893

I owned a 1990 celsior in Japan. Now have a 1992 LS400. There are 2 fans in front of the radiator. My Celsior didn't have these. They are always on in my 92 LS400. Is this normal?

dc893

I think somebody put a electric conversion kit in it before I bought it. Shouldn't they automatically turn on and off?

cobalt91

Yes they should. If they arent cycling it may be a stuck switch. any problems with over heating? If the egine temp isnt coming down it may cause them to run constantly. Could be a number of issues.

dc893

no overheating. i think its maybe a switch

91LS400vgb

No, they normally shouldn't be running. They should be running if you either have the a/c running or if the water temperature has exceeded a threshold. Are you sure it is both fans or only one?
I just posted a wiring diagram at https://www.clublexus.com/forums/ls4...urning-on.html.

If the engine is not hot and the a/c is not running, then there are several things that could be wrong:

1) It is possible that a relay is not operating correctly, but if this were the case, I would think that most likely only one of the fans would be running unless more than one relay was bad..
2) Check to make sure that the electrical connector is connected to the water temp switch at the bottom of the radiator. If it is connected, then check for a bad ground connection at the connector which would be equivalent to the switch being always open.
3) Could be a bad water temp switch or bad a/c high pressure switch.
4) Could be a problem with the wiring

dc893

I got it to shut off. Thank you.

cobalt91

What did you do?

dc893

It wouldn't shut off. I just bought the car also. It was just runnin non stop. Then it just shut off and started acting normally. All I did was start looking at it and trying to decide where I should start looking first. Hope its fine.

TDIGREEN1

Hijacking this thread back open because I have the same problem: both electric fans run at low speed all the time. So far:

-water temperature switch - this switch is normally closed according to the wiring diagram and apparently opens at 181 or 199 degrees water temp. When I pull the connector the fans go to high speed - which I think is correct. If I jumper wire the female plug the fans go to low speed.

- checked the fans with AC on and evap fan on high - both fans run on low speed.

- pulled the No 1. cooling fan relay - fans stop. replaced - fans run on low.

- pulled the No 2. cooling fan relay - fans runs on low. replaced - fans run on low.

- swapped cooling fan relays - fans do not run. swapped back - fans do run

- pulled the RDI Fan 3 relay and fans stop. The solenoid is getting 12 volts at all times when the ignition switch is on - ac turned on or off

So the ECT (water temperature switch) appears good. There is a question about the No. 1 CF Relay. The only other switch in this circuit is the A/C pressure switch - but I don't understand how it works in the circuit - when pressures exceed the resting state? Like over 100 psi on the refrigeration circuit?

I will pull the AC pressure switch connector but don't know what that will tell me.

I'd appreciate any suggestions. Wonder what this thing is worth - this 93 LS is a cherry ride but youngest is graduating - time to buy Momma a new car...
Thanks.

LScowboyLS

the first thing I would do is get the genuine Lexus wiring diagrams for your year (about $40 at Faxon auto literature)

TDIGREEN1

I am using these two sections I thought were from the manual.

LScowboyLS

yes, those pages are definitely from the real factory shop manual, I was just saying that the full wiring diagrams are very useful when trouble shooting a problem like this and they are very cheap at $40

I cannot substantiate that the manual pages you posted are from the correct year as your car, but on the other hand, I have no reason to believe they are not the correct year.

TDIGREEN1

I think it is the AC pressure switch but confess I'm having real trouble understanding this circuit. Is the AC pressure switch supposed to be open when the AC is off? Then it would close on a rise in pressure completing the low speed circuit to the fans. So with the AC off and the key on the No. 1 cooling fan relay should be deenergized - meaning that if it pulls in with the key on and AC off it is bad?

TDIGREEN1

Son of a $%#& - I think one of the relay solenoids was dropping out due to low battery voltage. Fully charged the battery and the circuit works properly. Will check alternator output voltage and buy at least one new fan relay.

Cowboy - thanks for the reply - you made me think.

TDIGREEN1

Uh-oh. Now I realize that new leak from the PS pump is directly over the alternator - which might explain a low voltage problem.... time to search the threads some more....remember something about an o-ring replacement....sure hope the alt is not bad.