Radiator fan (both) not working

On my 1999 Transport 3.4 both fans are not working. Fuse 1 and 6 are OK, if AC is on, the fans are NOT working. If I connecting the fans directly to the battery, they work fine.
Could it be the relais (if so, where can I find the relais) or the Computer?
Josef

Long time no see....Josef. ...wanted to say hello. this model has those components controlled by the Body Control Module, (RH Right Passenger Side kick panel), not sure if relays are remote or plugged onto the module itself but their shape suggests the latter option http://www.bestvalueautoparts.com/Replacement_Parts/PONTIAC/MONTANA/Radiator_Fan_Relay.html

What are your indicators? How do you know they don't come on? Is engine temp guage in the red? Do you boil over at drive-throughs? Is a/c not working?

Cooling fan(s) are not commanded on by engine computer until engine temp hits 227 degf. which can only be had by an extended idle (perhaps 30 min) at 80 deg ambient. Fans typically don't run while driving.

Cooling fans do not come on until a/c head pressure hits 175 psi. is your a/c up to that?

This is all done so as to improve fuel economy, why have fans on when you don't need them?

To test, merely jump tghe cooling fan relays in your underhood fuse box, if fans come, you are most likely okay.

>>>What are your indicators?
All normal until driving slow uphill. Then temp goes up to 100 Celsius and Water in expansion starts bobbling.

>>>How do you know they don't come on?
They don’t turn. If I but current to the fans, the engine is cooling down from 100 to 45.

>>>Is engine temp gauge in the red?
Not read but around 100 after Uphill and not moving any more or after motorway (130km) and stopping without switching of the engine.

>>>Do you boil over at drive-throughs?
If I have speed (wind) there is now problem. Only on slow drive and under pressure (uphill).

>>>Is a/c not working?
Actually, AC is not cooling very well. I have to reload the fluid for the AC.

>>>Cooling fans do not come on until a/c head pressure hits 175 psi. is your a/c up to that?
Where can I see the pressure? Should I reload the AC first?

>>>To test, merely jump tghe cooling fan relays in your underhood fuse box, if fans come, you are most likely okay.
Could you tell me witch of this relays are for the fan? I have uploaded a jpeg of my fuse box. To remove or detach the relays do I have to pull them out? They seem to be fixed to the box.

Josef

Hello to you. Thanks for the link. I have to check, if the relays is broken. Brcidd has given my some indications.
Josef

You may not have an issue, 100 degC is merely boiling point, fans are not supposed to come on until above that.....Yes it cools more when fans are forced on, but the system is allowed to go over 100C without fans on--

If you have purging in reservoir, then radiator cap is in question.

If you arfe losing coolant, than I would ask, have you ever had the lower intake manifold gasket replaced? 3.4L engines are prone for that one leaking.

The relays are clearly marked in underhood fuse box- jump the switched terminal connections of all fan relays to see fan operation.

>>>If you have purging in reservoir, then radiator cap is in question.
I will replace the cap.

>>>If you arfe losing coolant, than I would ask, have you ever had the lower intake manifold gasket replaced?
Is there a thread explaning how to change the lower intake manifold gasket?

>>>The relays are clearly marked in underhood fuse box- jump the switched terminal connections of all fan relays to see fan operation.
I have several relays. How are the relays for the fan operation marked? On my last message I uploaded a foto of the fuse box. Can a remove the relays pulling them hard out of the sockets?

Josef

The intake manifold gasket is probably the most common issue of any 3.4L engine owner-- do a forum search on LIM, or the like.

The relays come out hard, like you say, I usually use a pair of pliers to aid in that, they are labeled under the lid- turn lid over and see the relay/fuse map.

... if AC is on, the fans are NOT working.....
With your last remarks about a/c pressure/possible low r134 level, I'd like you confirm that the a/c clutch for the compressor actually engages when you turn the a/c on. The low pressure limit switch on the a/c system will inhibit the clutch from engaging and at same time will not engage the fans.
But I think your experience with vehicles , including roaming through south america with the Mercedes , means you have already considered this...
BTW, I think remembering you had an older model TS before..'98....right? Is this '99 recently acquired?..or is it a typo error ?

>>>I think remembering you had an older model TS before..'98....right? Is this '99 recently acquired?..or is it a typo error
Your are right, It's a 98 model! I just ordered a new cap for the rediator and in a few day I will bring the car to the garage to charge the AC.
Have a nioce day, Josef

The problem is resolved.

Replaced the Radiator cap with a new one. Charged the air condition system. Now the fans are working like they should.

One the radiator cap is a mark with arrow to "white tube" and arrow to "fan". I presume, that white tube means the tube to the expansion Reservoir. Is this so?

Thanks for your help about my fan problem.