radiator fan relays 1 and 3 keep blowing

Its pretty simple from a circuit standpoint. What is odd is its blowing relays. Usually you blow fuses. So you have to be reasonably good with a multimeter and first determine if the coil or the contacts on the relays are burning out. The contacts are the switching power part of the relay and the coil is part of the control. Next one might measure the current being drawn with a dc amp clamp (a more specialized meter).

I would speculate that one of the fans is drawing excessive power but not enough to blow the 30 amp fuses that feed each relay. Or the 30 amp fuses have been replaced with significantly higher rated fuses by mistake. In any case, excessive current can burn out relays but from the sounds of it your problem would have to draw less than 30 amps but much higher than normal for the fan. My guess would be one of the fans is partially or intermittently shorted.

By the way relay 2 will cause the fans to run at reduced speed and current so there is an outside chance a failure with it may cause an over current when it changes position.

Bottom line: This is a simple enough circuit that any halfway decent mechanic should be able to diagnose it quickly. Given you are risking your engine I would get someone to find the problem.

 

It would be great to know what you mean by the relays being "blown". Are the coils burned out? Or has something happened to the contacts, or they failed mechanically.

Something happening to the coils would be downright weird. Excessive fan draw wouldn't explain it.

 

A possibility is one of fans has a bad bearing and when #2 and #3 relay energize there is not enough voltage to start the fan. An electric motor that is stalled will draw a large current. If the fuses are oversized its possible the relay contacts may burn.

Another scenario is an intermittent frequently cycling coil which forces the contacts to see starting surge currents almost continously combined with excessive arcing of the contacts. The first scenario would probably point to fan #1 where the second scenario might be a result of an intermittent break in the common battery power to this circuit.

The third and most likely scenario is bad assumptions or an inaccurate description of the problem. For example it may be assumed the relays are bad because installing new ones "fixed" it. But it could be a wiring fault that was jiggled in the process. An inaccurate description could be the fuses are blowing rather than the relays.

 

Relays and fuses are side-by-side in the underhood box. Perhaps a component identification error is included in the OP's presentation of the problem?

 

I think we have a failure to communicate.

 

The fuses are in back right of the engine compartment. But if the fans both run with the AC then the fuses and the relays are 99% sure to be ok. Plus the fans are not even necessary at speed since enough air flows through the radiator.

Idle, slow speed and stopped is when fans become energized. You probably have a cooling system problem like a water pump, thermostat or even a head gasket. If you value your vehicle take it somewhere and have it diagnosed.

By the way, if you pulled out the first relays and tried to operate them using a 12v battery you could easily smoke the normally closed contacts through a wrong connection. Again, if the fans run in AC mode, the fuses and relays are ok.

 

With a good scan tool you can turn on and off the fans and verify when they are running. Same should be possible on the water pump. Realize it has two water pumps, one fo the engine and another for the inverter. There are coolant water tests for head gasket problems. Sometimes you will get white smoke (water vapor) out of the tailpipe when you have a bad head gasket. It would also use water to the point where their was not enough.

 

Techstream is the scanner from Toyota but its expensive. The “car scanner” app can see most of the data and works with a bluetooth obd2 reader. Some data:

 

Take a picture of the area of the fuse box were you replaced the relays and try to identify the relays changed. There are three involved. It is possible both fans would run in low but not high in some failure modes. Relay 1 and 2 of the above diagram have to work to go to high. The green wire LG enables high while the blue wire L is low.

 

"Whats really happening is its spraying out of the reservoir from the pressure relief valve under the cap"

You may have a blown head gasket that is leaking cylinder combustion pressure into the cooling system. That combustion pressure would exceed the 15 psi rating of the radiator pressure cap and be vented through the cap and possibly into the overflow container. You might check the coolant level in the radiator overflow container.

 

I guess we should take your findings at face value that somehow your relays failed (maybe by putting a 12v battery directly across the contacts) and replacing two seemingly “fixed” it. The thing is there are three relays used to run two fans. As it turns out, number one fan relay could be burned and you could still have low speed on both fans. When it tried to go high, one fan could then stop. A long shot but you probably need to check (or maybe just replace) the fan relay you did not change. See pics of fuse box and of the current flow highlighted in yellow for low and high fan speeds.

You can test relays with your meter on ohms only, no power applied by checking for continuity across the coil as one step and continuity across the normally closed contacts. Then you could power it with 12v on the coil only, listen for the click and check for continuity across the normally open with the coil energized. If this does not make sense then find somebody who does. Or just shotgun it (eg change parts and fuses).

 

Can't say that I have ever watched the behavior of the temperature at high speeds but I would expect it to hold steady. First, fans have nothing to do with air flow through the radiator at 70 mph. There is plenty of air flow already. Fans are for slow speed and idle conditions.

What happened on the combustion leak (head gasket) test? This is important.

I might wonder about that thermostat you changed. Perhaps its sticking closed too long? Maybe 230F occasionally is ok. I suppose it could be an intermittent water pump but that would likely make it overheat at any speed or even idle at times. So I would think that is not the issue.

 

Have you changed the radiator cap?