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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I'm having an apparent issue with the Radiator Cooling Fans

Resolved Question:

Hi. I'm having an apparent issue with the Radiator Cooling Fans on my '03 Chevy Venture.
JA: Has the car been overheating? Have you checked the fuses?
Customer: I've checked the two fuses and they are good. A little background on the overheating question.
JA: What is the make/model of your car?
Customer: '03 Chevy Venture
JA: Are you fixing your Venture yourself? What have you tried so far?
Customer: It sprayed coolant all over the engine yesterday when I was on a short trip. A local shop found that a 3-way coolant fitting somewhere on top of the engine was old, brittle, cracked and had opened up onto the top of the engine. They replaced the plastic fitting, and just before I picked it up, they discovered that the cooling fans were not operative. They worked on getting them operative, and I picked it up today. They didn't charge me more for the fan effort, but it now appears that they are not working. I have just a couple of questions about when they should be operative. I am able to connect to the OBD2 connector and read the engine coolant temperature. At what temperature should the fans be operative?
JA: Anything else you want the mechanic to know before I connect you?
Customer: Yes. The shop found that the connector to the fans appeared to have a burnt junction when they disconnected it and looked at it. They replaced the supply end of the connector.
Submitted: 8 months ago.
Category: Chevy
Customer: replied 8 months ago.
Continuing -
They replaced the supply end of the connector. I picked up the van and monitored the temperature on a live link to OBD2 and found that the temp gets up to about 228 degrees F without the fans running. This didn't seem right to me, so I wanted to dig into whether it's operating correctly and, if not, how to diagnose what's wrong.
Customer: replied 8 months ago.
I've checked continuity of the four leads on the supply cable to the vehicle ground and found that only one of those leads has continuity to ground. Looking at the fan side of the hook up, it is evident that the shop replaced only the supply side of the connector. The fan side of the connector still shows evidence of the burnt pin. I suppose it's still functional, but I don't know. I've thought about jumpering the fan to 12V just to see if the fans run manually, but I don't know how vehicle power is supposed to interface with the fan connector, so I haven't messed attempting a manual power up of the fans.
Customer: replied 8 months ago.
I know which relays are cooling fan relays, but I'm not familiar with how to check them for functionality.
Expert:  Jared D replied 8 months ago.

The best way to check the relays is by swapping them with another relay and see if the fans start working. You can also use a multimeter and a power source to test them, but it's not as easy. If you van has power options like a rear window defrost, power mirrors, AC, etc sometimes the relays are the same size and will therefore work to swap them with the cooling fan relay. Just don't use the ignition relay-or you won't be able to test the fans.

Once you have swapped in a relay, start the engine and turn the AC on- this will command the fans to run. If they don't then the problem is likely in the cooling fans themselves. Most of the time the problem is in the relay on these vans.

Customer: replied 8 months ago.
Hi Jared. Thanks for your response. I'm headed to bed, so I'm wondering if our schedules are going to be out of sync; however, I will look at this tomorrow morning. I will tell you a little bit of additional info about the relays that has me confused. 1) The main relay (#9 on my illustration) appears to have a black plastic cover on it, and when I pull on it, the cover simply comes off exposing the insides of the relay - not sure how to pull that one, and even if I did, it looks unique compared to the other ones.
2) The other relays (for Fan 1 and Fan 2) appear to be down tight. What is a good way to remove these relays? Are Channel Locks too aggressive? or can I use their wide jaws to grip gently on the sides of the relay to get a better grip for pulling up without damaging the relay? Or should I stick a slotted screw driver underneath the edge to help "unstick" it?
3) Finally, the A/C has lost freon (we planned to get it fixed in the spring, assuming we keep the van), and at last check it was operative, though not cooling well. It could be that by now enough freon has been lost that the compressor will not kick on. Will simply switching on the A/C start the fans, regardless of whether or not the compressor is running? If not, is there another sure fire way to switch on the fans?
4) And finally, I had asked about a temperature threshold that would start the fans. If you don't know this, it's fine, but I'm not sure that questions will be ultimately answered if the fans run with the A/C switch but don't run when the engine appears to be running quite hot. I assume you are stepping me through a process though, so I'll be patient and wait for that step.
Thanks again. I look forward to hearing from you and implementing your diagnostic process tomorrow. - Tim
Expert:  Jared D replied 8 months ago.

The fans should come one between 190 and 210 as long as coolant is flowing like it should. This engine has a problem of developing air pockets when there is a coolant loss, so make sure that the engine seems to be getting hot evenly. In other words, if the heater hoses or the upper radiator hose are cold when the rest of the engine is hot, then there is probably an air pocket in the system and you will need to add more coolant once you bleed the air out with the coolant bleeders. You will see a couple of bleed points on the engine where the radiator hoses connect. One looks like a bleed screw with a flat head slot on the top, the other looks like a brake bleeder. You should slowly open the bleeders one at a time with the engine warm to release air from the system. It will bubble air out until coolant comes out. Then close the bleeder and add coolant to the reservoir if it went down.

Expert:  Jared D replied 8 months ago.

To get the relays out you should be able to pull them out with wide jaw pliers. If they are stuck then you might have some corrosion in the fuse box relay slots. That might be part of the problem. You might have to force them out- possibly breaking them- so then they will need to be replaced regardless.

Expert:  Jared D replied 8 months ago.

If the AC doesn't have any freon the fans will still be commanded to come on when you turn the AC on. If you have a good scan tool that will perform function tests you should be able to command the fans on with the scan tool.

Customer: replied 8 months ago.
Thanks for the coolant info. This morning I was able to
- confirm that my compressor runs, despite being low on freon, so that's a non-issue,
- confirm that my fans do not run (in their current state) with the van running and the a/c on,
- remove all three relays w/ channel locks (they appear to be in good shape - just inadequate finger strength :-) ),
- confirm that I have no other comparable relays apart from the ignition relay which you said is not an option,
- rig a set of jumpers that will alligator clip to the hot and ground posts of the battery, and
- take a photo of the pins on the bottom side of the relays.
I have a monitoring tool for OBD2, not a scan tool capable of controlling the fans.
Is there a simple way of testing the relays with a set of jumpers?
I will check the coolant level as you have recommended.
Expert:  Jared D replied 8 months ago.

I was writing out how to test a repay but then realized that this is probably more effective:

He does a good job of showing how to jump power to the power side and then test the switching side.

Expert:  Jared D replied 8 months ago.

This one is pretty good too, but it's easiest with a power probe. Power probes are awesome for this sort of testing.

Customer: replied 8 months ago.
Hi Jared . . . my frustration with an aging vehicle is increasing. We began talking about a replacement as we went to bed last night.
First off, I found that there was some air trapped. I bled that off as you had suggested. But then I noticed spitting antifreeze spots above on the windshield and all around much like when it was leaking the other day. I held my hand above the belts and can feel sputtering on it. I look at my hand and there are dots of antifreeze. Not sure where it's coming from. Apparently this problem was never fully resolved. Unless this is residual fluid working its way to the belt and being thrown around. I suppose the only way to really find out is to pressurize the cooling system again with a hand pump cooling system tester.
Customer: replied 8 months ago.
Fan #1 Relay is defective. Always in the energized position, but with some resistance: ~ 74 ohms
Would this cause issues in particular? As I had mentioned in the initial discussion, one of the pin connections in the connector to the fans had been burnt. Wonder if this is somehow related.
Customer: replied 8 months ago.
Replaced the defective relay.
No change in fans - still not running. Thoughts?
Customer: replied 8 months ago.
With engine running and a/c on and functional delays in place no voltage on any of the 4 incoming wires to the fans.
Expert:  Jared D replied 8 months ago.

I'm sorry I was out all weekend. What was supposed to be a quick trip to look at an engine turned into an all day drive out to the middle of nowhere.

So it seems to me that the cooling fan driver in the PCM might have burned out. I've seen a failed relay cause that to happen once before. It's not very common.

I think your best bet is to see if you can get your hands on a scan tool that will command the fans on. If they still don't work then you know the PCM is the problem.

Customer: replied 8 months ago.
Jared, between the the lack of interaction with you, the lack of progress on identifying the issue with fans with a whole day invested, the a/c issue, an intermittent air bag light, 226,000 miles, and my wife's loss of confidence in the vehicle, it's time to cut our losses. We are going to get rid of the vehicle. Not sure how to proceed with paying you. I don't mind paying you more, but I'm pretty disappointed with your lack of communication to even acknowledge that you were doing to be unavailable. I'd like to minimize my payment to you and not give you negative feedback - I understand your situation. It's just that it ended up not being helpful toward a solution. We could have done more with it, perhaps, but the train has left and the momentum toward a different vehicle is high at this point.
Thanks - sorry it didn't work out. I hope you understand. How would you like to end this interaction?
Expert:  Jared D replied 8 months ago.

I can either submit to customer service that you be refunded for the whole thing, or I can open it up for a rating. I will receive 14 dollars if you give a positive rating.

I'm really sorry I was unavailable. The weekend just got away from me. I don't get to see what you have already paid to Just Answer, all I see is what I will receive from the rating.

Let me know which you would prefer- a full refund, or for me to open it up for a rating. I understand your frustration- I feel terrible for having let you down. The biggest reason I do this is to help people. The extra pay is nice, but I really just like knowing I've kept folks from having to get gouged by dealerships and rip-off mechanics.

Customer: replied 8 months ago.
I think it is a better deal for you to submit for a refund. I don't want to rate you poorly. I'm sorry that it works that way, because I appreciate the help that you provided. I think in the long, however that you will be penalized by the negative feedback necessary to limit what I have to pay. Interesting note - I was told that my cost if the problem was addressed and I was satisfied would be $28. Sounds like you only get half. Hmmm. Thanks again.
Expert:  Jared D replied 8 months ago.

Ok. I flag it for a refund. I get half huh? That's good to know- I've been doing this for about a year and never have been able to tell what my cut is.