SwedeSpeed - Volvo Performance Forum banner
1 - 20 of 22 Posts

·
Registered
2005 XC90 2.5T
Joined
·
243 Posts
Discussion Starter · #1 ·
Anyone know where the ECU fan is suppose to be? Is it underneath? I took off the cover to see what was going on because I'm getting the ole left rear door open plus dash going dead etc. batt is good but its acting like the ECU is overheating.
 

·
Registered
2005 XC90 2.5T
Joined
·
243 Posts
Discussion Starter · #2 ·
Of course if someone could post a VIDA/VARDIS diagram I would appreciate it. :)
 

·
Registered
2005 V70R, Midnight Blue, M66
Joined
·
2,124 Posts
Rear (toward firewall) of the ECU box, near the bottom. Easily seen if you pull out the PS tank and coolant tank. (They just lift out, without disconnecting hoses)
 

·
Registered
2005 XC90 2.5T
Joined
·
243 Posts
Discussion Starter · #4 ·
Rear (toward firewall) of the ECU box, near the bottom. Easily seen if you pull out the PS tank and coolant tank. (They just lift out, without disconnecting hoses)
:wave: super! Thanks Roger


Ed
 

·
Registered
2005 XC90 2.5T
Joined
·
243 Posts
Discussion Starter · #5 ·
Roger - quick question: found the ECU fan. Is it suppose to be on all the time? Is it definitely audible? I couldn't hear or feel anything when I had the car running and just 'on.'

Ed
 

·
Registered
Joined
·
491 Posts
It is audible. At least on my caR.
 

·
Registered
2005 V70R, Midnight Blue, M66
Joined
·
2,124 Posts
Roger - quick question: found the ECU fan. Is it suppose to be on all the time? Is it definitely audible? I couldn't hear or feel anything when I had the car running and just 'on.'

Ed
No, it is not on all the time.
It is temperature controlled via a sensor in the ECU. The ECU also provides the control lead for the fan.

When the key is on, there is 12VDC standing on the red lead of the fan. The ECU provides a ground to the black lead via internal temp sensor. You can check fan operation by turning on the key, and providing a temporary ground to the black fan motor lead.

Remember the fan is blowing air INTO the ECU box. It takes in cabin air via that large tube going through the firewall. Incoming air exits the bottom and sides of the ECU box.
 

·
Registered
Joined
·
327 Posts
----> Car Cabin Air ----> A/C at 25C ----> pipe channel to ECU box ----> ECU box/ECU ---> Air outlet in engine bay area

For discussion purposes on ECU Heat Insulation...

- the cool air from the passenger cabin (est around 20+Celcius) flows to the ECU box and out to the outlet to cool the ECU as required
- the black plastic box surrounding the ECU acts as Heat isolation from the engine radiant heat and does a good job keep the engine radiant heat away

By putting further heat deflectors inside the ECU box may have additional few single digit percentage points from radiant heat because it needs to pass the plastic box first, the added heat deflectors in order to reach the ECU.

Then again the ECU itself will be generating heat and the ECU heat is channel out through the box air outlet.

So far I've not heard of anyone having ECU overheat so the cooling system in the R based on cabin air cooling the ECU seems to work quite well.

But if you really need, either having the fan activated all the time or having a small aux fan installed to run and extract air out may help provide added cooling to the ECU..... something to think about if this is really necessary
 

·
Registered
Joined
·
4,280 Posts
If it's an overheat issue I would cut a square hole in the side of the box and install a PC fan to pull air out. They are all 12v and you could just wire it into a circuit that goes on /off with the ignition. If it were me I would probably get an LED lit blue fan just because. Also a very cheap solution (<$10)
 

·
Registered
Joined
·
713 Posts
If this helps the OP at all: mine tends to come on after the car has been driven in 75+ weather, and for more than 10 minutes. But it never runs more than 3-5 minutes after the car is shut off.

Have you taken yours out to clean it ?

Here is the diagram BTW:
 

·
Registered
2005 XC90 2.5T
Joined
·
243 Posts
Discussion Starter · #14 ·
Thanks guys - I'm going to take it out and clean it and let you know what I find.

FYI: I've read other posting here of an Ecu fan failing causing the ECU/CEM to act wonky. 04 S60R which is the same year as my wagon.

Thanks for the diagrams too guys - it's all helpful.


Ed
 

·
Registered
Joined
·
4,248 Posts
If your ECM get fried. And you get a no start and all kinds of other problems due to it over heating.....
Just drop it on the ground from about 4 feet up.
It's a trick the dealer won't tell you about...... But works vary vary good
Iv done 3-6 this way, never had a problem since...
 

·
Registered
Joined
·
2,155 Posts
If your ECM get fried. And you get a no start and all kinds of other problems due to it over heating.....
Just drop it on the ground from about 4 feet up.
It's a trick the dealer won't tell you about...... But works vary vary good
Iv done 3-6 this way, never had a problem since...
I can't tell whether I should take this seriously or be worried... :D

Obviously need some :beer:
 

·
Registered
Joined
·
4,248 Posts
I can't tell whether I should take this seriously or be worried... :D

Obviously need some :beer:
Unfortnely I'm 100% serious!!!! Lol the 1st time we "tried" his lol one dude was diaging the problem and when he pulled the ecu to check for injector single tested good, and as he was putting the ECM back in it slipped out of his hand.... Lol put it back in and car started. He did nothing but test and the drop...

Now here is what I figured. If there is a faulty fan or no fan at all, the ECM can reach temps from heat soak, that exceed the temp that melts or at least get soder loose..
So by dropping the ECM you knock what ever back in place......and wala hahaha
 

·
Registered
Joined
·
2,155 Posts
Unfortnely I'm 100% serious!!!! Lol the 1st time we "tried" his lol one dude was diaging the problem and when he pulled the ecu to check for injector single tested good, and as he was putting the ECM back in it slipped out of his hand.... Lol put it back in and car started. He did nothing but test and the drop...

Now here is what I figured. If there is a faulty fan or no fan at all, the ECM can reach temps from heat soak, that exceed the temp that melts or at least get soder loose..
So by dropping the ECM you knock what ever back in place......and wala hahaha
Wow. Just wow. DIY for the win??
 

·
Registered
Joined
·
4,248 Posts

·
Registered
Joined
·
2,155 Posts
1 - 20 of 22 Posts
Top