A/C after heater core change....

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fusioncruiser

A/C after heater core change....

Post by fusioncruiser » Fri 31 May , 2013 12:57 pm

Did a new heater core over the last few days but I have a strange problem now....

After I flushed the old coolant and replaced with rosella elc and recharged the A/C with R-134 all looked great from a heat and no leak perspective but the A/C is messed up.

The A/C is holding its charge ok and it blows pretty cool air out of the back unit but the front vents are all blowing hot air. Is that a vacuum line to a vacuum valve or a mixer that is off?

Any help would be great.

Thanks
Shawn

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Re: A/C after heater core change....

Post by chuck » Fri 31 May , 2013 1:27 pm

Could be many things. I'd check to see if your vacuum pump is working. Read through all my articles.
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Re: A/C after heater core change....

Post by fusioncruiser » Sun 02 Jun , 2013 4:03 pm

chuck wrote:Could be many things. I'd check to see if your vacuum pump is working. Read through all my articles.
I've read through them but I can't find where there is a test for the pump...
Also, the description for the mixer is that in a 98i should have a vacuum one but the pic you have of the electronic one is what I thought I have on the side of the heater box.

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Re: A/C after heater core change....

Post by chuck » Sun 02 Jun , 2013 4:29 pm

If you have a 98 it's all vacuum controlled. Get a vacuum gauge. I think you need 22 in of vacuum on the pump.
If you pull your control head out you will see a plug with a bunch of thin vacuum hoses.
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Re: A/C after heater core change....

Post by fusioncruiser » Tue 04 Jun , 2013 2:12 pm

Super. I'll pull the head tomorrow and test it there. Thanks

fusioncruiser

Re: A/C after heater core change....

Post by fusioncruiser » Thu 06 Jun , 2013 7:20 pm

So I pulled the head control unit and put the vacuum tester on the blacks but I don't know what number is supposed to be 22...

On the temperature control, there is a white hose and a black. On that black I get 15 in hg. (when engine is rev'd at 1500)

On the control for the vents and a/c and max a/c, On it's black hose, I get a ~ 6 or 7 in hg. (when engine is rev'd at 1500)

I can't find anything in the tech pages or my searches telling me if those numbers are low / high or good. If anyone could tell me, I'd like to avoid replacing the pump if it's not the problem.

Thanks,
Shawn

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Re: A/C after heater core change....

Post by chuck » Thu 06 Jun , 2013 8:48 pm

I seem to remember a line coming in through the firewall in front of the passenger compartment. I think it comes from the vacuum solenoid on top of the engine where the boost control is. But you proved that you do have a vacuum controlled system.
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Re: A/C after heater core change....

Post by fusioncruiser » Thu 06 Jun , 2013 10:18 pm

But are those numbers too low at the control head or are they where they should be? If they are good, then I'll move to test the various vacuum controlled doors next.

Thanks!

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Re: A/C after heater core change....

Post by chuck » Fri 07 Jun , 2013 7:08 am

Read my article on hvac problems. It has everything I know.
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Re: A/C after heater core change....

Post by fusioncruiser » Fri 07 Jun , 2013 8:47 am

I read it already it didn't have the info I need so I'm hoping someone else might have the numbers I need. Thanks

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Re: A/C after heater core change....

Post by JustinOK » Fri 07 Jun , 2013 8:34 pm

The vacuum pump should put out about 22" of pressure just as Chuck said.

I would check the pressure of the pump directly now, so find the line that goes from the pump to the wastegate solenoid and use that line to read the pump directly. This will help you find out if its the pump or if there's perhaps a broken and/or pinched line somewhere.
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Re: A/C after heater core change....

Post by fusioncruiser » Fri 07 Jun , 2013 10:34 pm

JustinOK wrote:The vacuum pump should put out about 22" of pressure just as Chuck said.
At what rpm is it to read 22"?

fusioncruiser

Re: A/C after heater core change....

Post by fusioncruiser » Sat 08 Jun , 2013 12:41 am

I found some reference stuff in the manual. Seems to say the correct number is 18" at the pump.

Also looks like my numbers were too low at the head unit too because they are supposed to be at idle and I didn't get the numbers they want.

Screen Shot 2013-06-08 at 1.37.54 AM.png
Might be the pump I guess.

Will do more testing tomorrow.

Thanks

fusioncruiser

Re: A/C after heater core change....

Post by fusioncruiser » Sat 08 Jun , 2013 2:12 pm

Tested pump and it was low at idle so I bought a new one from Napa... Problem now is that the pulley puller warped the pulley before it would come off.

Now I need to buy a replacement pulley but I can't find a cross ref part number. All I have is the AMG number 6006805.

Does anyone know if there is a corresponding Napa or GMC number I can use?

Thanks!

fusioncruiser

Re: A/C after heater core change....

Post by fusioncruiser » Sat 08 Jun , 2013 2:17 pm

I just found this GM part number... Hope it works: General Motors 15589757

It's $75 instead of $150 at Napa.

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