AC Clutch Not Engaging and Cooling Fans Not Working (I think)

[1999montana]

Interesting problem.

Just replaced the water pump due to seepage from the pump seal (hiding under the pulley) spraying inside the engine room. Was an easy fix; - one $58 lifetime water pump from PartSource and a new gasket...supplied.

Not a lot of room to work though, BUT the pump is right up there where you can get at it. The trick is in getting the weeping hole and the bolt holes to line up properly in the new pump. I fiddled with the darn thing for about a half hour...couldn't figure out why all the bolt holes wouldn't line up to start the bolts.
And to top it off, the new pump is a slightly different design so it was not as easy to compare one to the other. Got that done though.

Anyway, I noticed when I was diagnosing the coolant leak that the AC compressor would not engage. Figuring it was a low refrigerant problem brought on by old age (the van's - not mine!) and an aluminum cooling line under the van to the rear heater that perhaps might have ruptured, I dismissed the problem for now as one for a warmer day..who needs AC in February/March, right?

Well, I also noticed that the cooling fans will not come on even when the heat gauge reads 100+C and above. Revving the engine didn't cause the fans to kick in either, although the temperature did climb higher.

I read Greg A's extensive diagnostic on engine cooling, and began wondering if the fans will not engage because the AC will not function.

Don't know if the two 'problems' are related or just a coincidence, or just one big problem. Fuses are all good (continuity wise).

Any thoughts?

[LMP]

JUst in case this is A/C fan circuit labelled '97 ...must be quite similar for this item in '99 even i there have been several changes elsewhere ..
www.avigex.ca/xport/accircuit97.jpg
both fans must be connected and proved operational as they are connected in series for the LOW speed so current flows to the first fan and then exits and continues through the second fan, meaning each fan runs on 6-7 volts. I think Hi Speed will kick in only when the A/C is ON. That makes trouble shooting a little more complicated.

[rockwood84]

you mention that the holes in the water pump didn't want to line up. there is a top mark on the water pump some have an arrow some have a bump on the pump to tell where top is. they did change the blade design from the meat grinder look to one with a blade look. if the freon[134a] is low the clutch will not engage ,to keep from burning the compressor up should there be no oil in it.there are a few places that are common to leak there is a seal on the shaft behind the pulley, the bolt that holds the hoses to the compressor can pull out of the threads, some have had the condensor crack,also there is an o ring that is between the two halves of the compressor. i think the pressure should be around 40 lbs. as for the fans kicking on mine fan does not kick on until the temp hand gets a little above 1/2 mark then if it gets to 3/4 the other fan kicks on. if the a/c is on both fans will kick on a little above 1/2 mark.also the relays are under the hood in the relay box.

[1999montana]

All good information and very much appreciated. I will systematically check these things out.

After fiddling with the new pump and rotating it one bolt hole at a time, I finally got all 5 bolt holes to line up...the tiny notch you mention was on top....go figure! Stamping the word 'TOP' on the pump would have been too easy, I guess!

I remembered reading about the condenser somewhere here or in the Venture forum and haven't noticed the wetness the refrigerant and compressor oil leave behind in that area, YET!

To verify that the low pressure switch has disabled the compressor (due to low refrigerant), I'm going to temporarily by-pass the switch by jumpering across the connector (it's located near the receiver/dryer on the front, low left side of the chassis, I believe) to see if the clutch will engage. If it does, then we know the freon (R134a) has escaped somewhere.

Since I don't own a sniffer, but I do have a very good retired GM AC guy not too far away, when spring finally comes I'll take it to him and let him do some diagnosis.

I believe the last time I had a problem with AC on our Import, he charged the system with nitrogen and some dye so we could determine if it was leaking.

Right again about the low pressure or suction side...usually around 30 to 40 lbs ...so I'll let him test it out and report. If it is a seal or O ring, he can fix it, if it is a long runner line to the rear, I can fix it and return it to him for evacuation and re-charge.

The only thing I would like to confirm is that the fans are in circuit with the low pressure switch and clutch and when the AC circuit is disabled as described above, the fans are disabled too.

Seems silly that GM would do that, but who knows?