When should the electric cooling fan switch on?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Again, at what point or what temperature perhaps does the electric fan come on. I have been sitting in a parking lot for 30 minutesin 90 degree weather and it still does not come on. The truck and A/C is cooling properly.

Just figured it would come on by now. I have tested it with battery and it does work when given power.
 
When line pressure (high side) reaches about 220 psi (for a 100 series) it should come on.
 
My fan never comes on and the pressure has to be up to point where it should come on. Al fuses under hood are good and voltage straight from battery to fan WILL engage fan.

Why ya reckon it will not engage as it is designed?

Thanks
 
My fan never comes on and the pressure has to be up to point where it should come on. Al fuses under hood are good and voltage straight from battery to fan WILL engage fan.

Why ya reckon it will not engage as it is designed?

Thanks

Faulty trinary switch/connector or wiring would be my guess. There is also a relay.
 
Last edited:
Sweet. Yall Da men. Thanks

Just bought the same part for same price from same supplier as on Amazon and saved $10 shipping and guaranteed for Tuesday. We'll see.

Thanks again.
 
Last edited:
Make sure your new switch has a schrader valve in the end of it. Also check your wiring and connection.
 
Just picked up a series 100 LC salvaged with a front end collision. Repaired all/most damages but noticed that when the front fan on the radiator is plugged in it starts to turn on even when car is off. Whats the deal? Just curious.
 
To take pressure switch off, I am using a deep socket due to zero room for a wrench. When I try to turn the switch the aluminum lines are wanting to bend and there’s no stability when I’m loosening the switch.

Know of a better way?
 
To take pressure switch off, I am using a deep socket due to zero room for a wrench. When I try to turn the switch the aluminum lines are wanting to bend and there’s no stability when I’m loosening the switch.

Know of a better way?

You are fighting the oxidation that forms on the threads as a result of the two dissimilar materials. When you finally get the switch removed you will likely see the crusty white residue.

Unfortunately....applying heat or penetrating oil does not usually help in such situations, so...you are relegated to coming up with a way to support both sides of the tubing as near the fitting as possible and then just man-handle it off of there.

I would be inclined to CHECK the trinary switch, your connector and wiring before going any further though.

You should be able to 'jumper' the wire harness connection and see if your fan comes on. IF it does...then you have narrowed it down to the trinary switch. IF it does not...then you will need to start testing other components (relay, wiring, connector, etc).

If you end up needing to replace the Trinary switch...put a little Nylog on the threads and the O-ring. That way you will not have a leak and the switch will be easily removed later if ever necessary.

Hint: For those doing your own A/C work. "Nylog" is your friend. Get a bottle and use it. I have no affiliation with it, but hardily promote its use. It's good stuff, it works to help prevent small leaks and makes disassembly of mated parts easy (or even possible) at a later date. It is the 'anti-seize' of the refrigerant world.

nylog.jpg
 
Last edited:
trinary switch as in the pressure switch? I have tested the fan and it DOES work.
 
I think @flintknapper point is that you're going to have to evacuate and re-charge the A/C system to change the pressure switch so you want to be dead certain it is the switch before opening up the system.
If it were mine I would test everything else first and if the pressure switch is definitely the cause then have a refrigeration tech R&R the pressure switch because I lack the gear and knowledge for the refrigeration service work.
 
10-4
 
trinary switch as in the pressure switch? I have tested the fan and it DOES work.

Yes Sir. The Trinary switch is the pressure switch. It is so named because it monitors the Low Pressure, High Pressure and has a 'Medium' pressure range that once met...completes the fan circuit (its either a normally open or closed switch).

The reason I wanted you to check your new switch is to see if it has a schrader valve. IF it does...you can simply unscrew the old one (if you can get it to loosen up) and install the new one. If it Doesn't, you will need to evacuate the system before installing it.

But in either case....I would first check the wiring and connections to be sure it is the switch at fault. But not by just applying 12 volts directly to the fan. By doing that....you are 'downstream' of all the circuitry and have discovered nothing.
 
Gotcha thanks. Does not have schrader valve. I'll need to check on process for testing wiring and connections. Thanks
 
Gotcha thanks. Does not have schrader valve. I'll need to check on process for testing wiring and connections. Thanks


Check carefully, the schrader valve can be hard to see on some units. But some do NOT have them.

Trinary Switch.jpg
 
Thanks to @flintknapper I have resolved my issue with the condenser fan not running. The relay behind the bumper and right under the headlight was corroded at the Connection terminals. I replaced the relay and cleaned prongs and now it runs perfectly.

Now I’m wondering, if a condenser fan was needed for the ‘98-01 02 years, then what was changed in the cooling design for the newer models to no longer need a fan?
 

Users who are viewing this thread

Back
Top Bottom