Cooling fan

Hi all,

Lesabre 2001 custom, ~100K miles.

Lately, I noticed my car running hotter than it used to, i think this happens when the AC is on. I used to see the temperature reaches 224F then drops back in the DIC in normal city driving conditions, and now i see it reaching ~230F before dropping back.

My main suspect is one of the fan relays, as i have been told the fans should be running always when the AC is on, and I think i "caught" the fans once not running when my AC was on.

Now i saw three cooling fans relays under the hood, can someone explains me what each of them is meant for?

Thanks,
Gilmour

There are three relays.
1 - Low speed relay
2 - High speed relay
3 - S/P (Series/Parallel) relay

The PCM controls the fans by grounding the relays. When the low speed relay is grounded power is sent to the right fan motor then through the 'normally closed' contacts of S/P relay to the left fan motor and then to ground. This operates both motors in series which causes them to run at a slower speed.

The high speed relay & S/P relay are grounded at the same time. This sends power to the left fan motor & breaks the 'normally closed' contacts in the S/P relay. The right fan motor now has its own ground through the 'normally open' contacts of the S/P relay. This operates both motors in a parallel circuit which allows them to run at high speed.

Thanks for the prompt and comprehensive reply :smile:

should i assume all the 3 relays should be grounded (activated) when the AC is on (no matter what the temperature is)? or is it by a temperature threshold?

Thanks,
Gilmour

It seems like the fans would have to come on with the air conditioning so air would move through the condensor core. I'm not sure if it would be high speed or low speed.

Without the air on the the low speed fan comes on when the coolant gets up around 205 degrees. The high speed comes on around 220 degrees IIRC. I also think the fans turn off once the car reaches a certain speed.

Has the thermostat in this car ever been replaced? and you do need to make sure the fans are indeed running when commanded by the PCM...

The fans will come on when you turn the AC on, but the fan speed for the ac is dependent on system pressure... And for system temps its like stated above...

oooh, this is very useful information, i never saw the fan kicking on 205, i always noticed the temperature reaching 220 to 223 then the fan kicks and it drops back to ~210 and then back to 220 or so then back to ~210... and keep cycling between those two temp. while in traffic jam (never thought this is not how it should be - silly me!)- from this i conclude the low speed fan (or control) is not functioning right.

As for the thermostat, i am not sure if it has ever been changed, i never changed it since i bought this car a year and half ago, however, i do think it is OK, since i see it opening around 191 (feeling the hoses), and in highway driving it keeps my temperature round 191 - this is why i started suspecting the fans.

again,
Thank you all for your great help and support :thumbsup:

An update(?),

The fans, relays & fuses are OK, when the AC is turned on, the fans run at high speed, however, without the AC On - the temperature keeps rising till 223 then the fans starts (both at low speed i think).

Any clue how to approach this?

how many temperature senders are there?, i connected a simple ELM to the ODB, and the scan tool reads the same temperature as the DIC - is it the same temperature the PCM or ECM uses to control the temperature? or is there another sender/sensor?

Again,
thanks all for you help.

Hello everyone,


your help is really needed to approach this.

to summarize my problem: without the A/C running, the low speed fan doesn't kick at all, the temperature keep rising till 223 before the fans start running high speed.

checked the relays and they are fine (the 3 of them do function well when the A/C is on)
check the fuses and they are good, (both fans do run after all...)

any idea/clue ?

Thanks.