Engine Bay Blower voltage cycling between 14V and 10V - voltage regulator issue ?

[PaulRainbow]

Hi. Thanks for all the feedback. In response to a question the alternator is attached to a ECS163 quick charge separator.

Disconnect the fan and heck the engine battery voltage, with the engine running.

If the battery voltage is stable, it must be the fan or the fan wiring. Connect the fan directly to the battery to determine which it is.

If the voltage still fluctuates, swap the domestic battery and engine battery connections on the ECS163 and again measure the voltages at both batteries. Does the fluctuation move to the domestic battery and the fan perform as normal ?

 

[diversp]

Hi. Quite a debate going on here ! I disconnected the fan. Engine running the engine battery was stable at 14.1V. Agree it must be something relative to wiring for the fan or perhaps some errant controlller. I cannot see at all how the fan is connected to power without stripping out all the wiring and there is nothing in the manual on where it would be connected.

 

[PaulRainbow]

Hi. Quite a debate going on here ! I disconnected the fan. Engine running the engine battery was stable at 14.1V. Agree it must be something relative to wiring for the fan or perhaps some errant controlller. I cannot see at all how the fan is connected to power without stripping out all the wiring and there is nothing in the manual on where it would be connected.

If you connect a cable from the fan straight to the engine battery, you will know whether it's the fan or the wiring, depending on whether the fan speed fluctuates or not. My feeling is that it will be the wiring, but it's a simple check to confirm.

 

[Alex_Blackwood]

If you connect a cable from the fan straight to the engine battery, you will know whether it's the fan or the wiring, depending on whether the fan speed fluctuates or not. My feeling is that it will be the wiring, but it's a simple check to confirm.

As the OP has installed a new fan and both behave the same, I would expect an external, to the fan, problem. such as a wiring fault suggested by Paul. However, is it possible that there is some restriction in the outlet hose, There may be a speed or overload device associated with the fan motor which could conceivably be affected by back pressure on the fan?? or some sort of thermostat or other controller fitted in the circuit, which could be defective. Without seeing the system difficult to say so basically just "Flying Kites" He could connect a test lamp to the fan wiring, with the fan disconnected and see if it varies. The problem could also be caused with something varying in resistance, heating and cooling? The difference he noticed in the volt drop at the battery, which was less than at the fan does suggest something at the fan or in the circuit after the battery.

 

[omitdoc]

Did you ever find out what was causing the problem? Same boat...same issue!

 

[William_H]

OP mentioned (albeit 5 years ago) that the fan only operated when engine was running. Now did that mean only when power to the engine is turned on (key switch) or was it automatically only on when engine started. This latter might indicate a VSR for the fan supply or a relay connected to the alternator o the fan supply or a relay connected to the alternator centre of star connection. (that used for tacho) In this latter case there must be a cotroller for the fan some where.
As said check battery voltage then voltage at the fan. If it runs off engine 12v supply check voltage at panel. Just a few thoughts ol'will

 

[Refueler]

Something like this is worth investigating. My next check would be to disable the fan (should be a fuse that could be removed), then see if the engine battery voltage still fluctuates. If it does it further points to an issue with the fan itself.

Some of these old threads are really interesting !!

mmmmm if the fan is disconnected and engine battery still fluctuates - then surely its NOT the fan ???

Question to OP ... when engine running and alternator charging - WHICH battery is primary in the charging regime before VSR operates ? If the Alternator is charging Engine start battery as primary and its fluctuating - maybe this affects VSR and therefore domestic battery doesn't fluctuate and isn't it that second battery after VSR does not back feed ? It would not fluctuate if full charged ?

If the engine battery fluctuates when fan / all gear except engine disconn'd - then I think :

Battery may be suspect - but I would think that alternator regulation could be failing ... then it would be an idea to give alternator to a car electrics guy to run up and test.

Maybe there's a fuse or connection that is heating up causing high resistance ... then cooling ... heating up again ... ? Worth checking cables while running for any signs of heat etc. Recheck connections.

Glad that someone else noted that OP had already changed to a new fan and it still did same.

 

[PaulRainbow]

Some of these old threads are really interesting !!

mmmmm if the fan is disconnected and engine battery still fluctuates - then surely its NOT the fan ???

Yes, a 5 year old typo !

Question to OP ... when engine running and alternator charging - WHICH battery is primary in the charging regime before VSR operates ? If the Alternator is charging Engine start battery as primary and its fluctuating - maybe this affects VSR and therefore domestic battery doesn't fluctuate and isn't it that second battery after VSR does not back feed ? It would not fluctuate if full charged ?

If the engine battery fluctuates when fan / all gear except engine disconn'd - then I think :

Battery may be suspect - but I would think that alternator regulation could be failing ... then it would be an idea to give alternator to a car electrics guy to run up and test.

Maybe there's a fuse or connection that is heating up causing high resistance ... then cooling ... heating up again ... ? Worth checking cables while running for any signs of heat etc. Recheck connections.

Glad that someone else noted that OP had already changed to a new fan and it still did same.