Overheating, high speed fans not kicking in !!!

[scyan]

Hey guys, I have overheating issues when I come off the highway and do some city. My problem is, the fans work but they dont switch to the higher speed by themselves ! I mean they spin. But if my car is cool and I turn the AC on, the fans dont spin at all and they should at high speed, right ? So I think that when it gets hotter, they never spin fast enough to cover the heat. Now, how do I fix that ??

Thx,

Scy

[doyuhvanhonestshop]

Originally Posted by scyan

Hey guys, I have overheating issues when I come off the highway and do some city. My problem is, the fans work but they dont switch to the higher speed by themselves ! I mean they spin. But if my car is cool and I turn the AC on, the fans dont spin at all and they should at high speed, right ? So I think that when it gets hotter, they never spin fast enough to cover the heat. Now, how do I fix that ??

Thx,

Scy

We have the same problem. Along with all in my sig line.
Temp gauges rise to way higher than appears reasonable and when the fans do come on they don't run very fast either. Wasn't aware they had multiple speeds.

It also has some weird heat problems. Temp gauge will show plenty hot, but little or no heat inside. Drive about 100 yds and you get hot air. Makes no sense to me.

[1999montana]

Originally Posted by doyuhvanhonestshop

...Temp gauges rise to way higher than appears reasonable and when the fans do come on they don't run very fast either. Wasn't aware they had multiple speeds....

Doyuhvanhonestshop:

Are you sure you have an overheating problem? The problem with your gauges may actually be a 'constant' voltage regulator (CVR), usually part of the instrument gauge cluster (but may be located somewhere under the dash).

When the van is running all of the accessories, gauges and anything that draws power runs off the alternator, not the battery.

The CVR's purpose is to regulate the voltage going to the gauges (so that they read properly) during periods when the alternator is under load or charging full tilt. The CVR is different from the voltage regulator (internal to the alternator, I think), which monitors battery voltage.

Someone reading this post that has access to wiring diagrams should be able to confirm the CVR’s existence and location for you.

It could also be as simple as a bad ground in the cabin or to the battery itself. Again, a good wiring diagram could help you trace the grounds in the cabin, particularly to the dash cluster. Usually the grounds are black, but not always.

You may find if the CVR is your problem, the fans and the cooling system are operating just fine.

Hope this helps…

.

[Mike_EX]

What about the Fan Relays in the Fuse/Breaker box in the Engine Compartment?
(2000 Montana) My fans do not come on unless the A/C is on; then both fans come on and the Temp gague goes down. There are two fan relays in there. I believe that one works based on the engine temperature and the other relay is switched in when the A/C button is pushed to be sure the fans come on whenever the A/C is on. I haven't done any testing yet. Are these relays identical electrically so I could switch them and see what happens? Thanks.

[GregA]

Originally Posted by Mike_EX

What about the Fan Relays in the Fuse/Breaker box in the Engine Compartment?
(2000 Montana) My fans do not come on unless the A/C is on; then both fans come on and the Temp gague goes down. There are two fan relays in there. I believe that one works based on the engine temperature and the other relay is switched in when the A/C button is pushed to be sure the fans come on whenever the A/C is on. I haven't done any testing yet. Are these relays identical electrically so I could switch them and see what happens? Thanks.

Here is a link to how the cooling fans work. This is for a 2001 Chevy Venture (sister of the Montana), but I believe it is the same. Includes schematic (wiring diagram).

Engine Cooling System

Take Care,