Cooling fan causing engine to surge when kicking on

[burke985]

And only when it kicks on and it just started happening recently , I've swapped out the high and low relays and the 40a fuse for the cooling fan relay itself none of the old relays or fuse looked bad or had any rattle in them and issue still persists. I logged the voltage and it drops to below 12.5 when fan kicks on then quickly comes back alive to 14.4 v. I have already upgraded the cooling fan to the gt500 fan like 1.5 years ago I guess. Anyone have any idea what this could be don't wanna have to take it to the dealership and get charged 100 bucks or more if it's something simple and I can easily fix. I have a flex fuel tune on the car from Aed and it does it on both performance and drag versions . Anything else I'm missing to check thanks in advace there is little to no info online about this .

 

[Slowb00st]

And only when it kicks on and it just started happening recently , I've swapped out the high and low relays and the 40a fuse for the cooling fan relay itself none of the old relays or fuse looked bad or had any rattle in them and issue still persists. I logged the voltage and it drops to below 12.5 when fan kicks on then quickly comes back alive to 14.4 v. I have already upgraded the cooling fan to the gt500 fan like 1.5 years ago I guess. Anyone have any idea what this could be don't wanna have to take it to the dealership and get charged 100 bucks or more if it's something simple and I can easily fix. I have a flex fuel tune on the car from Aed and it does it on both performance and drag versions . Anything else I'm missing to check thanks in advace there is little to no info online about this .

Battery or alt going bad!? Or loose connection.

 

[burke985]

Battery or alt going bad!? Or loose connection.

Checked the occurrence with my multimeter while the engine was running via the battery terminals and it didn't dip below 13.3v according to the meter when the fan kicked on or when AC kicked on . This is just weird only concerned because it's never surged like this at idle before. Getting good voltage readings there when fan off so idk what it could be.

 

[GBCoyote]

Bad ground somewhere?

 

[burke985]

Bad ground somewhere?

Just removed the roush Cai box and checked connection and it was clean and tight.

 

[GNBRETT]

check ur idle sensor that is most likely ur issue and make sure ur coolant is full cause it too if low can cause it to surge wen fans kick in

 

[burke985]

check ur idle sensor that is most likely ur issue and make sure ur coolant is full cause it too if low can cause it to surge wen fans kick in

Where is that located if you don't mind me asking. Would that be on the throttle body ?

 

[burke985]

This is what I'm looking at on left side of throttle body but part number calls it throttle position sensor.

 

[JpL4K3]

Fan resistor. Sounds like what I went through several months ago. Fan would kick on from nothing to high speed only. No low speed. Fan Resistor was burnt out.

 

[Blazer707@TBR]

When did this start happening?

 

[burke985]

When did this start happening?

I guess a couple weeks ago

 

[burke985]

Fan resistor. Sounds like what I went through several months ago. Fan would kick on from nothing to high speed only. No low speed. Fan Resistor was burnt out.

Thank you so much for that info that was the problem .. it's a 160 dollar part but I still had my old stock fan so I just robbed it from there. It's the same part number as the one on the gt500 fan only difference is the length of the wires so I just spliced the resistor into the plug for the gt500 fan for the lenght and everything is working like a charm. Thanks again

 

[JpL4K3]

Thank you so much for that info that was the problem .. it's a 160 dollar part but I still had my old stock fan so I just robbed it from there. It's the same part number as the one on the gt500 fan only difference is the length of the wires so I just spliced the resistor into the plug for the gt500 fan for the lenght and everything is working like a charm. Thanks again

Glad I could help.