Radiator Fans ON & OFF at Full Speed when AC is Turned ON

Here in Pc, it’s obsolete to do searches. You have to feed it baby bird style for us.

 

I got to say that one stumped me I’ve never seen that one before.
Lucky you you win the prize. Lol

can you tell through vibration or sound is the compressor also turning off and on constantly ?

 

Get Techstream or similar capable scantool and see what the A/C system data is (what is the high pressure sensor displaying?)

When you had the system recharged, how long was it evacuated beforehand? How and who recharged it? What were high and low side system pressures after recharging?

If there is still air in the system or it was overcharged (or a bad pressure sensor makes it think the pressure is too high) then you could be "bouncing" off the system's high pressure cutoff point. That would also explain the high radiator fan speed.

You need to know what the pressures ARE and what the ecu THINKS they are.

Posted via the PriusChat mobile app.

 

Did you solve this issue? I am having the same problem... Mine got a front end crash and was repaired and is now exhibiting the same problem.

 

Yes I believe you are correct I forgot about people grossly overcharging the Prius and it instantly going in the 400 psi banging on the fans immediately into high speed and then going over 440 psi in immediately cutting off the compressor.

The pressure falls down cuts back on the compressor immediately high speed fan then immediately cuts off the compressor again and keeps repeating the cycle.

I’m banking on your one decision that somebody overcharged it it only takes two or three extra ounces to do this as I released a video before showing over 400 psi with two extra ounces of refrigerant

 

Prii have a nifty way of wiring the two fans, where there is a low speed achieved by putting the two in series across the 12 volt supply (so each fan sees 6 volts), and a high speed achieved by paralleling them (each fan sees 12 volts). The series/parallel connections are swapped around by the three fan relays.

You can search up some existing threads here that include that wiring diagram.

It not uncommonly happens, in repairing a front crash, that somebody misses a detail of that wiring, usually the series connection for the low speed, and then the result is the fans don't operate on low. That means they're not cooling the A/C at all when the controls want them on low, and as a result the controls will keep bumping them to high when the pressure or temperature rises, and then back down to low (where again they don't run at all).

A similar thing can happen if one fan just doesn't work. Because low requires both fans in series, there won't be any low if either fan doesn't work. Then the system will keep bumping to high, where only the working fan will work.

 

I am going with the overcharged theory. Screwing up the fans' series wiring while preserving the parallel wiring seems less likely. Especially if both run in High.

Low is with Relay 3 Pulled In

 

It's a pretty recognizable syndrome when it happens though. No low-speed operation, which means the temperatures and pressures quickly spike to the trigger point for high speed, and then decrease again quickly with the high fans. So instead of just running nicely on low, the system repeatedly bounces between high speed and no fans.

 

Any fix to this issue I seem to have it too after a new motor was installed.. any help would be appreciated

 

Fix will depend on what's causing it, not always the same. If you grab a meter and follow the wiring diagram above, shouldn't take too long to pin down.

 

I found out my cause. 1. the drier bag was filled with oil. and after that, it did the same thing with fans running on full blast, which turns out to be overcharging of the system. once the right amount went in. the fan speed cut down, and a/c blows cold.

 

Hello everyone I have the same fan problem always at high speed and non stop when cold setpoint since I put gas with duracool 12a, what should I do? It looks like the pressure in the high-pressure circuit is too high.

 

Evacuate, vacuum and recharge by weight. Ensure variable speed compressor is on full.

 

I wonder if everybody will ever eventually learn there’s only one correct way that works 100% of the time that gives you 100% correct results that gives you 100% factory performance.
No, guessing
No estimating
No, I think
No, it works most of the time excuse

Just a simple Evec and recharge by weight only with no exception to that rule

It only takes about 15 seconds to completely recharge with liquid refrigerant in a Prius every time all the time 100% of the time no excuses accepted.

 

Ok can air conditioning specialists do that? Most of the time it's a refill

 

I checked the speed of the compressor fan, it goes to 6500rpm for a low setpoint, the motor fan runs constantly and at 20 degrees Celsius it runs intermittently. Can we have more information with techstream? I have no possibility of having it immediately but if it is useful I will manage. No error code goes back so high pressure flow not high, or below the max range?

 

Yes a specialist can do it. These ac systems are nothing like most standard vehicle systems. Be sure existing gas will be removed, new gas is weighed in and they understand it is a variable speed compressor. It MUST use special oil, not standard poe or mineral oil.

It should not be a hydrocarbon based refrigerant with additives like duracool 12a. Use R134a if that was originally used.

It is not exactly clear what your symptoms are based on your posts. We don't know the year or model.

Describe parts as radiator fan, compressor and evaporator (cabin) blower. Is it cooling well? How do you know its high pressure?