Revs drop when radiator fan comes on

[Eastcoastrs2]

Hi all,

When the radiator fan on my rs2 comes on the revs and voltage drops.
This only happens when sitting at idle and is worse if the aircon is on too.
Feels like the car is about to stall but it never has.

Had the battery checked by an auto electrician and he says it and the alternator are
fine. He also said I should clean the injectors as this can sometimes be the problem.

Has anyone had this problem or know where i should look?

[Ross]

You always get a bit of this due to the extra load on the engine. With mine it's pretty severe (car labours and lights dim due to voltage drop) and you sometimes here a bit of electrical noise from under the dash, which is the relay. I'm trying to get a replacement relay 324 for mine which should sort it.

[Eastcoastrs2]

Mine labours as well like it almost stalls.

Is that the fan relay? and by electrical sound do you mean like a buzzing or a hum?

[rynaqui]

I may have this issue as well but only in standing traffic

[caterpillar]

may the fan engine have some dry bearings or likely.. the the el engine drain high amps...or, what volt are the geneartor gives.. 12,3 volt or?? 14,4-14.7....its ok..

[Error404]

The 500w ABY fan draws a lot when it kicks in, it will dip the revs. Sounds pretty normal.
Ross I'd say your "electrical" sound from the dash might need some attention

[PeteRR]

Yep, mine does exactly the same thing too (revs dip momentarily).

[handy andy]

Same here on my RS2,but only a slight drop just as the fan kicks in.

It was the same with my S2,nothing to worry about i would say.

[DFrosty]

Hello Gents

I have an RS2 fan in my '83 urq and have to constantly blip the the throttle to keep the motor from cutting out completely whilst in traffic or stop lights...quite the pain in the ar*e sometimes. Been researching a way to fool the motor into kicking up the revs by thinking the aircon has come on. Might you lads know anything about this??

Cheers

Apologies to OP for threadjack!

[Thecrispynoodle]

On the AAN the ecu/ISV compensate for that immediately, revs jump back up to target idle rpm as soon as air-con clutch and/or fan kick in. Assuming that ABY/ADU should behave the same then you might have some underlying issues (e.g. Inaccurate MAF signal, dead O2 sensor, holed BPV or PCV valve etc) resulting in an air/fuel mixture outside of the adjustment range that struggles with the extra load. Pull DTCs see if anything like a 561 present.

[Error404]

AFAIK the ECU only outputs to the HVAC it doesn't know when the AC is on per se, it adjusts the idle speed to compensate for the extra load.

[newsh]

I agree, boost leak test and pull codes

Check idle switch is working on throttle body.

Wash ISV out with WD40 or GT85.

[prj]

AFAIK the ECU only outputs to the HVAC it doesn't know when the AC is on per se, it adjusts the idle speed to compensate for the extra load.

ECU knows when AC is on.

[Error404]

I stand corrected. Out of interest, where does it take its signal from? Rad fan stage 1 relay or something?

[prj]

I stand corrected. Out of interest, where does it take its signal from? Rad fan stage 1 relay or something?

Pin 41, you do the rest.