Poor idle when fan comes on - solution?
- Thread starter pietro
- Start date
When you operate some of the bigger electricals in the car (including the fan)...the engine is slowed by the drag caused by the higher electrical load on the altenator.
Normally when you switch on a big electrical....a solenoid valve should open in your carburettor...this opens an extra fuel way that slightly increases the idle speed to compensate for the load.
I think your solenoid is not operating. It could be sticking...or the solenoid may not be getting its switched voltage.
I would NOT recommend adjusting your mixture to compensate if the fault is the solenoid valve.
I'm just goanna check out if theres any easy practical ways to test for this....
I'll be backkkk
Normally when you switch on a big electrical....a solenoid valve should open in your carburettor...this opens an extra fuel way that slightly increases the idle speed to compensate for the load.
I think your solenoid is not operating. It could be sticking...or the solenoid may not be getting its switched voltage.
I would NOT recommend adjusting your mixture to compensate if the fault is the solenoid valve.
I'm just goanna check out if theres any easy practical ways to test for this....
I'll be backkkk
OK, here it is...
There is a control unit under the passenger seat. This monitors electrical load. When the load reached a certain threshold, control unit opens the solenoid on the carburettor.
Here’s some tests
inspect the solenoid wiring
Inspect the connections to the control unit under the passenger seat
Check the fuse to this is good. (In my book its the right most fuse in the fuse box under the dash drivers' side. 15 Amp, Yours might be in a different place though, so if in doubt check them all. Check if this fuse is even there....)
Unplug the solenoid wiring and connect a volt metre across the wiring harness. All electrics off...start engine...turn the rear window heater or headlights on and off...check that the voltage changes between 0v (ish) and 12 V (ish) on the volt metre.
To check if the solenoid works....disconnect and reconnect the battery negative lead (be aware of loosing your stereo security code and clock etc). Listen close to the carburettor...you should hear the solenoid clicking as the battery lead is connected and disconnected. You might benefit from the use of an enthusiastic volunteer!
Testing the control unit is fiddly so assume its working for now....come back to it if all else fails.
Let me know how you get on
Rich
There is a control unit under the passenger seat. This monitors electrical load. When the load reached a certain threshold, control unit opens the solenoid on the carburettor.
Here’s some tests
inspect the solenoid wiring
Inspect the connections to the control unit under the passenger seat
Check the fuse to this is good. (In my book its the right most fuse in the fuse box under the dash drivers' side. 15 Amp, Yours might be in a different place though, so if in doubt check them all. Check if this fuse is even there....)
Unplug the solenoid wiring and connect a volt metre across the wiring harness. All electrics off...start engine...turn the rear window heater or headlights on and off...check that the voltage changes between 0v (ish) and 12 V (ish) on the volt metre.
To check if the solenoid works....disconnect and reconnect the battery negative lead (be aware of loosing your stereo security code and clock etc). Listen close to the carburettor...you should hear the solenoid clicking as the battery lead is connected and disconnected. You might benefit from the use of an enthusiastic volunteer!
Testing the control unit is fiddly so assume its working for now....come back to it if all else fails.
Let me know how you get on
Rich
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pietro
Ex. Club Member
Wierd...
I checked to see if the idel solenoid control unit was working and I can confirm that it does. I know this beacuse I first turned the car on, I then swiched everything I could on (except the radiator fan of course). The car began to struggle. I then disconnected the control unit and the car struggled even more, I tried this a few times to be sure. What now? Is my battery or main HT leads finished? The battery is new, although it does look rather small, other wise do I reguire an upgraded altenator? Ideas suggestions? Thanks
I checked to see if the idel solenoid control unit was working and I can confirm that it does. I know this beacuse I first turned the car on, I then swiched everything I could on (except the radiator fan of course). The car began to struggle. I then disconnected the control unit and the car struggled even more, I tried this a few times to be sure. What now? Is my battery or main HT leads finished? The battery is new, although it does look rather small, other wise do I reguire an upgraded altenator? Ideas suggestions? Thanks
Hi,
Assuming your existing battery is fine, a bigger battery alone would not help, because as soon as the engine is started, the system voltage goes higher than the battery terminal voltage....12.5V to 14.5V (ish). So, once the engine is started, the source of all current comes from the alternator.
If you’re convinced that the alternator is at fault then the standard one should be fine if either repaired/reconditioned or replaced.
A bigger battery will allow you to run electrical without the engine running for a little longer. Or will allow you to draw larger currents from the battery while the engine is off (for starting and electricals)
A bigger alternator will allow supply more juice (current) to the devices in your car, but I’m not sure that the existing wiring will be rated high enough to carry higher currents than the standard alternator can supply (melt…smoke…fire?).
I’ve been thinking about the slow idle thing and I must admit I'm pretty stumped!
You could eliminate the alternator if you have a mate with a K10 that will let you borrow theirs (known to be in good order…..fast idle is working on their car) to try....better than shelling out just yet?
The only other thin I can think of is that battery might be dicky? Does your battery get hot after 5 or 10 min of idling?
Perhaps you could borrow a mates battery as well to test with?
Assuming your existing battery is fine, a bigger battery alone would not help, because as soon as the engine is started, the system voltage goes higher than the battery terminal voltage....12.5V to 14.5V (ish). So, once the engine is started, the source of all current comes from the alternator.
If you’re convinced that the alternator is at fault then the standard one should be fine if either repaired/reconditioned or replaced.
A bigger battery will allow you to run electrical without the engine running for a little longer. Or will allow you to draw larger currents from the battery while the engine is off (for starting and electricals)
A bigger alternator will allow supply more juice (current) to the devices in your car, but I’m not sure that the existing wiring will be rated high enough to carry higher currents than the standard alternator can supply (melt…smoke…fire?).
I’ve been thinking about the slow idle thing and I must admit I'm pretty stumped!
You could eliminate the alternator if you have a mate with a K10 that will let you borrow theirs (known to be in good order…..fast idle is working on their car) to try....better than shelling out just yet?
The only other thin I can think of is that battery might be dicky? Does your battery get hot after 5 or 10 min of idling?
Perhaps you could borrow a mates battery as well to test with?
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