JAndersson

Have done some searching but couldn't find the information I wanted. So here is my problem and question:

Problem:
The fan in front of the condensor never turns on when the AC is on. I assumed the blower was busted so I took out the fan assembly. After that I did some measurements with a volt meter on the plug that connects to the fan to see if I could get some readings (12v) but I couldn't (the car and the ac was of course on). So then I connected the fan directly to a 12v source and it started to spin so it works. Continued to do some measurements on the plug (it has 4 pins). For example did I check witch of the pin who was connected to ground. And it turned out that all of them where!

Questions:
So what causes my problems? Can it be some problems with the cooling fan relays? See picture below

If the relays is the problem, how can i test them to find the faulty one? And does anyone have any better picture or description on where to find the relays. If it's not the relays that causes my problem, what can it be then?

And could anyone tell my what the part marked with red circle does? It's connected to 2 of the pins in the plug that connects to the fan.

A close up:

Couldn't find the part on this exploded view:


Thanks a lot!
/Joel

JimsGX

Maybe this will be of some help... 2nd page

JAndersson

Thanks a lot. Now a know where the relays are located. Remember that I did see some relays when I took out the left headlamp assembly to change the lights. That must be the cooling fan relays.

Still, does anyone know how I should test them to see that they work.

Thanks!

JAndersson

Hello again. Done some more measurements now. First of all. I think a have figured out what the thing marked with the red circle in pictures in my first post is. It must be some type of temperature sensing device which only let a current pass if the temperature is high enough. And one of my problems must have been that the pins on this thing was very oxidized. Because when I first started to measure the resistance over it the ohm meter showed it was infinite. But some times it went down to zero. So I cleaned the pins and after that the ohm meter showed that the resistance was zero.

Has also checked the relays and they are working fine. They are of the always closed type (I think). When the voltage over them is zero they let a current pass true. And when you put 12v over them they don't. I have only 2 of them in my car. But then I have only one cooling fan. And it's from here it get strange.

When the car and the ac is on the both relays get a voltage of approximately 13v. So they opens. That means that no current can pass to the fan. Because after some more measurements I figured out that the current must pass true the first relay to the fan via the "temperature thingy" and the second relay. Or something like that. I'm in no way any electronics expert. So it seems that my problem is that the relays get a voltage. Any idea what can be wrong?

One thing that hit me was when I had took out relay no. 1 to do some measurements and started the car the radiator fan started to turn even when the engine was quite cool. And I'm quite sure it hasn't done this before. And it continued to behave the same way even when I put the relay back. So can it be that something else brooked when I started the car without cooling fan relay no.1 in it
And that the cooling fan is wired so it will not turn on if the radiator fan is on?

So then my final questions for now are; Why is my radiator fan always on? Could it be some problem the engine coolant temperature switch in the bottom left of the radiator?

Will call Lexus on Monday. But I'm afraid that people like Pure Drifter and others on this forum actually knows more about the LS400 then the most Lexus technicians in Sweden because the LS400 is not an common car in Sweden. I guess it just a few hundred of them.

Thanks!
/Joel

JAndersson

My cooling fan in front of the condensor will still not turn on. The Lexus technician bypassed the temperature sensor in the radiator and that made the fan to start. So got the sensor changed, but the fan still doesn't work. So today I decided to start a subscription at alldatadiy to see if I could find the problem my self. And I think I found the cause of my problem. But I have to check it to morrow. Found this text on how the AC system actually work;

"Operation at low speed
During A/C operation, when the pressure of A/C Compressor becomes higher more than 1323 kPa , 13.5 kg/cm2 192 psi ) than normal pressure the A/C high pressure SW turns OFF . As a result, Cooling Fan Relay no.1 turns OFF and the current flows from FL RDI Fan --> TERMINAL 2 of Cooling Fan Motor no.1 --> TERMINAL 1 --> TERMINAL 4 of Cooling Fan Relay no.3 --> TERMINAL 5 --> TERMINAL 3 of Cooling Fan Relay no.1 --> TERMINAL 4 --> TERMINAL 2 of Cooling Fan Motor no.2 --> TERMINAL 1 --> GROUND , flowing to the Fan Motor in series, causing the Cooling Fan to rotate at low speed."

For more information see attached pdf.

My plan is to remove the connector, which if I have understand this correctly, will be connected to the pressure switch. This should make the fan to start. If the fans start that will confirm that the pressure switch is bad and need to be replaced.

Or what do you think. Am I on the right track?

JAndersson

The pressure switch is now changed and that fixed my problem. When the pressure in the AC system reached 14 bar the fan in front of the condensor started to spin.

Nohawk Lex

iTrader: (5)

I have a similar problem. One day, I was going on a long drive. I had my A/C on and after some time, no cool air was coming from the vents and then the A/C light on my climate control started blinking. When I got home, I found the code from LexLS.com that states that the compressor is locked. I didn't question this and replaced my A/C Compressor and even converted it to R134a (just today). The problem is, well I still have the same problem. NO A/C. The magnetic clutch isn't turning so I started diagnosing. I bypassed the compressor straight to the battery and it worked so the problem is probably in the power delivery to the compressor. I checked the relay as well but I didn't know how to check for continuity so I decided to just pull it off. I started the car and turned the A/C on, no cool air. I then installed the relay back and I felt the click and immediately checked the magnetic clutch and it works! But after a few seconds, the clutch would shut off again. I attempted this several times and the same thing happens. At this point, I have no idea what the problem is. I have the wiring diagram for the A/C but I can't find a thread about this problem. I'm thinking worst case scenario that the problem is my climate control unit but I'm really hoping not. I really hope someone can help me on this. Sorry for the thread jack. My 2 month old baby can't ride in the car especially under the San Diego sun without A/C HEEEEELLLLPPPP!!!

Nohawk Lex

iTrader: (5)

Anyone know where else the A/C Magnetic Clutch Relay is hooked up to? I know one is ground, the other to the climate control but 2 I'm not sure where it leads to. I only have the wiring diagram for the A/C which doesn't tell me where this leads. Need real help guys!

JAndersson

Have you checked the pressure in the system? If the pressure is to high, the magnetic clutch will disengage.

Have found some information on how to check the Compressor Magnetic Clutch Circuit. See attached pdf. Hope this helps.

Nohawk Lex

iTrader: (5)

I haven't even put enough freon in the system. So far just 12oz. We decided to check the compressor because it didn't seem to be sucking the freon. That's when we realized that the clutch wasn't engaging.

Nohawk Lex

iTrader: (5)

Thanks for the PDF file. I haven't had time this weekend to check my electrical but I will this week and update you guys on what I find.

Amskeptic

I am late to the party, sorry.

It shuts off quickly because the compressor draws down the low-side (suction side) and triggers the low-pressure switch which is opening the circuit to the clutch. Then as low-side pressure increases with the non-operating compressor, the switch closes and the compressor cranks up again.
Short-cycling is almost always due to low charge.
Colin
(p.s. the pdf link above has an incorrect diagram. 2-4 is supposed to be the contact side of the relay, 1-3 is the control coil side. In the illustration, it shows the coil on the 2-4 side)

LILEVO

iTrader: (1)

Any idea what it means when my AC fans run 100% of the time?

My AC suction line is also covered in frost from the compressor all the way to the low port at the firewall so I don't think the compressor shuts off when the AC is running. I'm thinking they are related.

Bill Dowd

Iv'e have the same thing happing to my fans I found that they don't cut in until the outside air is hot then they will cut in mine usually cut in in heavy traffic or but when I am running on the road they don't come on I also washed the condensor and radiator in a self carwash to help keep down heat I also found a bunch of road garbage between my radiator and condensor a lexus tech showed how the area get full of stuff my at 239,000 miles was 1/3 to half full. I also get frost on my A/C hoses and my sight glass is full no bubbles my temp goes down to 32 degrees

willhickey

iTrader: (1)

ah i hate ac work