Aircon and idle speed

[tristanjustin]

I hope somebody can shed some light on my problem - eversince i had my bongo(a year ago) my normal idle speed is 800rpm. Everytime i turn on the A/C the rpm jumps to 850rpm. Just last week when i opened my A/C instead of going up it went down to 700rpm, which resulted to engine vibration.Sometimes it goes back to normal operating mode but most of the time it does not anymore. Can anyone share their ideas as to how i can get my bongo back to normal ( 800rpm in idle speed and when a/c is turned on it goes up to 850rpm instead of going down). Thank you in advance. TRISTAN

[richrich]

I think mine drops in revs when the a/c is on ? Not sure but will check later. I thought that's normal (extra strain on the engine)

[tigger]

I'm fairly sure I'm right in saying that, under normal conditions, turning the AC on should never result in revs increasing. I am at a loss to explain why this should ever have happened - the only thing I can think of is that it was on all along and that you were actually turning it off(!)

However, it is utterly normal to experience a drop in revs when the aircon goes on. AC places quite a lot of extra load on the engine - hence the associated increase in fuel consumption. And when it first starts up, the extra load really is quite substantial. I sometimes actually feel my Bongo slow perceptibly when I'm driving along and I first pop the AC on.

I would suggest that, if idle is rough when your AC is on, it is because someone has turned the fuel pump down too far in order to get it through the emissions test and/or to try to improve fuel economy. Try turning it up gradually, testing it with AC on and off at each increment, until you are happy with the idle. If you can't find a happy medium - ie it idles too fast with AC off at the lowest idle speed that prevents vibes with AC on - then I'm out of ideas except to suggest that there's something wrong with your aircon system that's causing it to place too much stress on the engine. Job for a specialist?

tigger

[dandywarhol]

When the aircon is turned on there's a soleniod on the fuel pump which (should) increases the idle speed back to normal. To save opening the engine hatch to check this, lightly touch the throttle pedal (don't press it) and then push the aircon button - you should feel the throttle pedal drop a few mms.

Tigger's explanation sounds good to me - someone could have tampered with the pump OR maybe the aircon needs regassed and it's affecting the idle by cutting in and out through lack of gas pressure

[Chin]

If you lift up the driver seat, you can see 3 or 4 ( can't remember clearly) solenoid valves (black in colour) in a row. the one which is nearest to the front of the car will pull an actuator and apply some force to the thottle control arm when air-aon is on, thus higher RPM as more fuel is applied. Check this solenoid as it could be faulty.

[tristanjustin]

Thank you to all that contributed their ideas on my problem and chin was right its my solenoid that is busted i had it changed and the whole problem went away Im really glad as a bongo owner to have a website like this to run to for advice(s) from the "EXPERTS"! Thanks to all again.- Tristan