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Early e24 HVAC Troubleshooting

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G03rt2
Posts: 51
Joined: Sun Nov 05, 2017 11:48 am
Location: Wisconsin

Early e24 HVAC Troubleshooting

Post by G03rt2 » Sat Dec 01, 2018 10:13 pm

Hopefully I'm remembering all of this right since the car is taken apart right now.
When I put the temp on hot, and turn the blower on, and vent selection is "normal" only cold air comes out of the vents.
When I put the temp on hot and leave the blower motor off, but turn the vent to defrost, after the car warms up, very hot air comes out of the defrost vents and some hot air down below too.
I also have an issue if I put the temp on cold, and turn the vents to off, I almost get a ticking/weird noise from 1500-3500 rpm range that sounds like it's coming from under the dash.

I've bled the coolant system using the method where you hold one hose up high and blow into another (i forget where I learned that from)
My next plan of attack is to look at the coolant system hose work/piping that was done during the motor swap (previous owner had it professionally done) I've seen a "T" in the hoses and wonder if the way the lines are ran are maybe causing some sort of issues.
I know the early cars have a very impossible-to-get-to heater valve so I'm trying to make that my last resort. Seeing that I get hot air from defrost I wouldn't think that's the case.

If anyone has experience with this, I'd appreciate the comments.

HVAC panel for reference.
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IMG_20181201_153118.jpg
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Pod
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Re: Early e24 HVAC Troubleshooting

Post by Pod » Tue Dec 04, 2018 12:48 pm

You obviously have a S1 car. I'm just wondering if you have aircon, as there is an extra fan which sits above the transmission tunnel which works independently of the fresh air fan mounted in the firewall in S2 cars and I would imagine its the same for the earlier models? No doubt somebody will correct me if I'm wrong :wink:

GRNSHRK
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Re: Early e24 HVAC Troubleshooting

Post by GRNSHRK » Tue Dec 04, 2018 5:12 pm

G03rt2, got this PDF file most likely from the "Big Blue Book" for US cars :-?

Other than Pod's potential observation that you may have aftermarket A/C, which was fairly common in Euro cars, the venting and operation of the knobs and levers should all be the same [-o<

HTH :wink:
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6er vent system - early.PDF
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G03rt2
Posts: 51
Joined: Sun Nov 05, 2017 11:48 am
Location: Wisconsin

Re: Early e24 HVAC Troubleshooting

Post by G03rt2 » Tue Dec 04, 2018 5:47 pm

Pod: I HAD an aftermarket AC, it was poorly done, I didn't like it, and I live in Wisconsin, so it was all tore out including the blower under the dash.

GRNSHARK: That PDF is VERY helpful, and a bit comical. With that air flow chat, it seems like my system may be operational with the exception of the front side vents maybe having broken ducts or something. It's "interesting" that the front center vents would be for cold air only.

I'll have to track down that weird noise, and possibly why the front side vents aren't blowing hot, but other then that it seems all is in order.

bpoliakoff
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Re: Early e24 HVAC Troubleshooting

Post by bpoliakoff » Tue Dec 04, 2018 8:36 pm

At the same time, I don't know what can be " ticking" under the dah. But there is a flap on the condenser box that can have rotted out seals onit. I know when i went through mnine is was bad. It can also be stuck open leaving all kinds of air flow through it . There are also mechanical shafts with bevel gears on them thaat control parts of the meechanical aspects of the system that should be checked as well. It seems to me the fan is blowing but air is coming ing through and the various entry points have to be checked. The heater valve could be kaput but I think if it is it would leak liquid. It is a pita to change but not that bad. =IIRC it takes a 10mm open end wrench. It's just tight getting in there. The "T" in your system is original.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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