heater core going bad?

[BSOD2600]

The past week, I've started to notice a sweet smell in the cabin while driving. Sure smells a lot like antifreeze. Also some times notice an extra amount of moisture on the inside of the windshield even though it might be dry outside. Sure sounds a lot like the heater core is going bad.

Before I drop $200 for a new one and countless hours replacing it, is there any easy way for me to really check that is the source of the problems? I don't see/smell any coolant leaks in the engine bay, nor notice the overflow tank level dropping. Don't see any wet spots on my carpet. I already tried putting in some of that radiator silver fix stuff which you pour into the system, in hopes that it would plug whatever small hole has developed -- it didn't do jack.

[BSOD2600]

Noticed something else today... Had the climate control set to Defrost and cold temp, since the window was getting fogged up at the bottom, even though its dry out. After a bit, it got cleared up. Then I changed the temp to hot and immediatly saw a literal cloud of water vapor spray up onto the window. Blew cold defrost again for a bit to clear stuff up. Repeated the hot temp, and sure enough the vapor cloud shot out of the vents again.

Is there any other reason why this type of thing would be occuring, or is it a sure-fire sign that the heater core is leaking?

[Legacy777]

I'd say it's a pretty good indicator it's your heater core.

Only other verification I could think of would be to pressure test the cooling system and see if it holds pressure. It will probably slowly leak down.

[BSOD2600]

OMFG, I've spent the past 5 hours getting the whole dash, etc torn apart. Wasn't able to get the heater box out without discharging the A/C system (grrr broke a tube to the evaporator canister too). Finally got the damn box out and sure enough, heater core was wet all around the bottom. Sort of see liquid between the grills all up and down the center too.

Now just waiting for the DHL saturday delivery of the new core...

[Legacy777]

That sucks dude!

That is one job I really wouldn't want to do.

[skid542]

Ah man. I completely feel your pain. I had to do the same thing when my car starting getting filled with a fine antifreeze mist.

Someone here claimed to have replaced their heater core without discharging the AC system. I don't know how though. I wasn't able to and it sucked as my AC blew ice cold.

Good luck with getting it back together - somehow I missed a connector or did something but my cruise and rear defrost haven't worked since putting the dash back in.

[BSOD2600]

The core arrived some time this morning around 9am. Worked on it from 10:30am till 1pm. Got the dash, wheel, cluster, etc reconnected. Still some more wiring / cleanup under the dash to do, so at least another hour. Then to refill the coolant, fire it up and see whats broken.

I called around to the local Subaru dealers on getting the A/C fixed/charged. Part 73052AA380 (~$65) got twisted (I was dumb and didnt see the other nut on the evap side since it was hiding behind the rubber). Since the system has been opened up, they also want to replace the condensor 73020AA120 (~$165). The A/C is ~$50 and then the recharge itself is $150. In total, about $500 to make the A/C system work again. DAMNIT!

Once the car is working again, I'll post up some of the pics I took for reference to help myself.

[BSOD2600]

Got the dash reassembled, fired up the car and let it idle for a bit while I attempted to get any air out of the coolant. Noticed that my temperature gauge doesn't move at all now. Even when the HVAC was blowing hot air, no movement from the temp gauge. I'm not about to drive the car around without that working either.

I suppose the only way is to start tracing lines (1992_legacy.pdf - pg 852) for the temp gauge to find the problem?

Also, the ABS light is always on too. ARG!

[Legacy777]

The dash temp gauge uses a separate sensor then the ECU coolant temp sensor. Did you burp the coolant system of air via the vent on the passenger side of the radiator?

Why does the dealer want to replace the condensor? The condensor is the exchanger in the front of the car. The evaporator is what's in the cabin. The only thing that needs to be replaced is the receiver/drier. Your system should already be r134a.

[BSOD2600]

The dash temp gauge uses a separate sensor then the ECU coolant temp sensor.

Well since everything was working before I removed the dash, I'm fairly certain that its electrical inside the cabin... somewhere. I'll just have to follow the wires (gah!) using that handy FSM you posted and see what I find.

Did you burp the coolant system of air via the vent on the passenger side of the radiator?

I thought that was only on N/A cars? I don't recall having anything like that on mine. Always burped it of air by massaging the upper hose into the radiator and leaving the coolant condensor tank open until the thermostat opened up. Then the level drops and one can put in more coolant. The odd thing is that this time, the level in the condensor didn't drop even after the engine was warmed up. I could feel the hoses to/from the heater core were hot and slowly the hose to the top of the rad was getting warm too.

Maybe I lucked out and don't have any air pockets? I didn't drain the coolant (as the manual suggests), just disconnecte the heater core hoses and lost a little coolant.

Why does the dealer want to replace the condensor? The condensor is the exchanger in the front of the car. The evaporator is what's in the cabin. The only thing that needs to be replaced is the receiver/drier. Your system should already be r134a.

Not really sure. I checked on the availabilty for that part I bent -- lmao January 2009 aka it's not made anymore. So I think I'll just get the AC system recharged and see how it holds up. If it does leak/fail, then I'll get another tube from the junkyard.

[ericem]

Only problem is you can't do a vacuum on the system. that is something your probably going to need a shop to do or if you have a neighbour in hvac he can do it for you. Just get the R12A from a auto part store which is good for r12 and r134a system. You need about two bottles. Drier might be bad only one way to find out. Not sure if a short time being disconnected will damage the drier.

[BSOD2600]

Only problem is you can't do a vacuum on the system. that is something your probably going to need a shop to do or if you have a neighbour in hvac he can do it for you.

Yup, found that out the other day when looking around on Google for my options for the AC recharge. Think I'll just take it to a shop, make sure they pull vaccum for 15 min and it holds, then get it refilled.

[BSOD2600]

During the core replacement, I took some pics to help me remember where stuff went, screw positions, etc. Nothing really that special, but might help those in the future:

My heatercore site.

Not really sure how people could replace the core w/o removing the A/C evap unit. Both the fan motor housing and heater core, have a big plastic lip which curves around the back of the AC evap. Due to that, the heater core's pipes sticking out the firewall and the framework in the driver area, there isn't enough slack to move it out.
Example of the lip:

[BSOD2600]

ARG! I can't figure out why my temperature gauge isn't working! Also it seems the 1992_legacy.pdf FSM which I'm using is wrong for my 94.

For example the FSM:


On my car, the RY & WG connectors are on this connector that goes into the cluster:


According to the FSM, it goes into B96 which is a big black connector... like this (top right):


Yet, when I do a continutiy test between the I22 and B69 connectors, I don't get anything for the RY wire -- only the WG on various pins (many are green or blue stripped which I assume is grounding).

On the otherhand, I CAN trace the RY wire to this smaller connector:


I then trace where the RY wire, which goes into the ECU. Is that what the "MPFI control unit" refers to?

But there is still a problem with that! The FSM page 69 shows that for turbo's the pins out of the cluster I should be tracing are A4 & A8. Well A4 on the connector is WG, but A8 actually is RG! That RG wire goes into the giant wire harness bundle which goes up behind the dash.

WTF! Anyone have ideas on what to do to further troubleshoot?

[BSOD2600]

Boy do I feel dumb!

I gave up and put the whole car back together. Took it for a drive around the proverbial block. Just as I was coming home the temp gauge... started to move!! Sooo.... seems like I wasn't giving the car enough time to register anything on the temp gauge, even though the heater was blowing hot air and the idle was ~600 rpm. DAMNIT!

Well now just to deal with the Airbag light constantly on now...

[Legacy777]

Just to note, that PDF you're using is for the overseas cars. You need to get the other one from my site that is for the north american cars.

[BSOD2600]

Oversea? doh! How would one know that when the cover states 1992 service manual?

The one from your site, as in http://www.main.experiencetherave.com:8 ... ual_scans/ ? Your site seems down to me.

[BSOD2600]

hmm your 1992_Subaru_Service_Manual-Engine_&_Wiring.pdf manual is missing part of section 6-3 Wiring Diagram.

[skid542]

With regards to the airbag light - did you go through the whole 're-center' routine before you put the wheel back on. I also had a light and it turned out that I didn't get the connector from the bag itself and the slip joint clicked closed. I had it pushed together but it hadn't clicked and fully located itself. Felt pretty dumb when I realized that was all it was.

This is all assuming you pulled the wheel to get the dash out.

[Legacy777]

Site is back up. Server rebooted and had a weird IPSEC issue. Yes I know the book is missing some parts. The 90 legacy wiring diagrams has all of that section I believe, and is in the FSM scans section.

[BSOD2600]

With regards to the airbag light - did you go through the whole 're-center' routine before you put the wheel back on.

Yes, I made sure that center plastic ring 'center' was lined up with the outside 'center' mark. Didn't double-check the connector though. Guess I can do that easy enough.

Yes, I did pull the wheel off. Had to buy a cheap $10 puller too.

The 90 legacy wiring diagrams has all of that section I believe, and is in the FSM scans section.

Ah thanks, even though its too late . At least I've got it for next time.