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PostPosted: Sun Mar 19, 2006 9:55 am 
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Joined: Sun Mar 19, 2006 8:39 am
Posts: 7
I need some help with a cooling problem on my 1999 venture 3.4l. Last week I noticed that when I waiting in traffic the temp started to rise to half way on the temp gauge. Once I started to move the temp retruned to normal. I appeared to be a thermostat going bad. So I replaced it. After a week the van is doing the same as before.
I noticed that when the temperature rises the cooling fans do not turn on. I hear what sounds like a clicking sound but they do not turn on. I disconnected the cable to the fans and tested each lead with a circuit tester, but there apppears to be no voltage going to the fans. There are several relays in the fuse box that controls these fans. There are no blown fuses.
At 40000K the intake manifold gasket let go and oil mixed with anti freeze.
My questions are?
1. Is there any way to test the relays without buying new ones. And how many control these fans.
2. Can I hard wire the fans to see if they work.
3. If the sensor is bad, will it cause the fans not to turn on.

I prefer not to take it to a dealer, well you know about dealers.

Thanks in advance for your help,

John


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PostPosted: Sun Mar 19, 2006 3:19 pm 
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Joined: Mon Jan 02, 2006 12:14 am
Posts: 237
Location: Silicon Valley
Hi John,

Welcome to the forum and thanks for the question!

First, check out this page. It is the cooling system fan details for a 2001 model, but I think they are pretty much the same.

Cooling System Fans

Quote:
My questions are?
1. Is there any way to test the relays without buying new ones. And how many control these fans.
2. Can I hard wire the fans to see if they work.
3. If the sensor is bad, will it cause the fans not to turn on.

1) There are three (3) relays. I believe the easiest way to test the relays would be to switch the Air Conditioner ON.
As long as you have refrigerant in the A/C system, this should turn the fans ON (could be low-speed or high, depending on the refrigerant pressure). You should also be able to SWAP relays around, as long as they are the same part number. There is a link to the relay diagrams on that page I mentioned above.

2) You could directly connect a battery to each of the fan connectors to test them. But if switching on the A/C turns the fans on, you won't have to do this.

3) If the Engine Coolant Temperature (ECT) sensor is not working right, it could keep the fans from turning on at the right time. There are some testing and troubleshooting steps here.

I almost forgot - The symptom you mentioned (temperature gauge going to about half way in traffic) is the same thing my van does. It usually goes just above the half way mark while stopped (traffic or drive-thru) and then go back when I start moving or switch on the A/C.


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PostPosted: Sun Mar 19, 2006 3:21 pm 
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Joined: Sun Mar 19, 2006 8:39 am
Posts: 7
Thanks Greg.

The funny thing about this problem is that it just started.


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PostPosted: Sun Mar 19, 2006 3:42 pm 
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Joined: Mon Jan 02, 2006 12:14 am
Posts: 237
Location: Silicon Valley
jdv2 wrote:
Thanks Greg.

The funny thing about this problem is that it just started.

No problem John.

Yeah - Relays DO go bad after a while. If you go to the maintenance part of the site (here), I have a story there about when one of my relays (for A/C) went bad. Its listed under "Air Conditioner Clutch Relay" in May of last year.

Take Care,


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PostPosted: Mon Aug 08, 2011 6:15 pm 
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Joined: Mon Aug 08, 2011 6:01 pm
Posts: 1
Location: United States
New to board but was impressed with the detailed info and work done by the members.

Sorry to resurrect a very old thread, but it fits the problem I am having.

I have a 99 venture. The cooling fans will not come on to cool things if I am not running the AC. Running the AC turns the fans on. Without AC, I have seen the gauge go as high as 3/4 to 7/8 on the temp gauge, which according to a gauge posted on this forum puts the temp between approx 240 and 247. That is as high as I have let it get. I have red at other sites that the cooling fans will come on when it gets to 'red' on the gauge but I feel they should come on sooner.

The fans seem to switch from low to high with the AC running.

I have tested the relays with multimeter after energizing them and they appear to engage properly with little resistance on the closed circuit (not sure I have a good meter to test the resistance amount, but they do have a closed circuit).

The temp was running dead cold at interstate speeds so I replaced the thermostat (not an easy job) and that solved the problem. I have also replaced the temp sensor next to the thermostat.

Does anyone have any idea what to check next?


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PostPosted: Wed Sep 12, 2012 1:58 pm 
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Joined: Wed Sep 12, 2012 1:49 pm
Posts: 3
Location: Toronto
Hi Just joined

It appears no-one can solve the Venture over-heating problem as out-lined on this form. As a follow-up question is there a way to hard wire the fans to run n low speed. In my view It appears the above problem may be a sick ECU/PCM. Replacing an ECU has many costs.


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