NO HEAT!!!

E28 technical advice asked and given! Troubleshooting, modifications and more.
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tsmall07
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NO HEAT!!!

Post by tsmall07 »

So it got cold as balls all of the sudden and my heat isn't working. (yes I know heat doesn't come out of the face vents) It doesn't come out with just the air vents open or with the blower on. What could cause that to happen?
bmw4aaron
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Post by bmw4aaron »

I'm assuming your blower motor is working? Let me guess, you get heat at idle or low speed driving? If so, R&R the valve on the firewall. You can get a complete new one for a few hundred bucks or a rebuilt kit for 30-50 bucks.
BMWCCA2
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Post by BMWCCA2 »

Usually either the thermostat or the heater valve. Symptoms for either are sort of specific if you can elaborate. Of course could be both, too. It's cold out there today.
skip535i
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Post by skip535i »

If it's the heater valve, not only can I walk you through the replacement, but I also have one for you...cheap.
Brad D.
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Post by Brad D. »

I'm gonna guess heater valve.
tn535i
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Post by tn535i »

If it's the t-stat the temp gauge will not come up or come up very slowly and the heat will be barely warm.

If it's the heater valve the gauge will come up but still no heat, maybe at idle like was said. In a pinch you can remove the guts of the heater valve and put the top and seal back on to get heat. In fact if you depressurize the system and then put the coolant tank cap back on when it's cooling down it will try to form a slight vacuum. Then you can remove the four screws on the valve body and loose very little coolant and be on your way with heat.
thesalboy
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Post by thesalboy »

Agreed - if the coolant system thermostat failed in the open position, you won't get coolant temp or will only get coolant temp slowly.

If you have coolant temp and still no heat, it is likely not a failure of the heater valve (on the firewall just below the brake booster) because the valve closes with voltage, and so would typically fail in the open position (= constant heat). It is possible that the valve could have failed in the closed position, but I have yet to find someone who can confirm firsthand that it ever has. If it has failed, there is a repair kit for $45 from Pelican Parts [p/n 64118390132] ($36 from AutohausAZ [p/n 1147213007] - my preferred parts source) consisting of the internal plunger and its seal/diaphragm. The entire valve now costs $300+ new.

To check for heater valve operation, Bentley states that when you turn the key on with engine cold and slowly turn the temp dial from cold to hot, you should hear the thump of the heater valve opening (it also cycles every 4 seconds when the set interior temp is reached). But I have not been able to hear anything from inside the car doing this test on a known working heater. Others have reported that applying voltage directly to the terminal on the valve permits verification of valve operation.

Even if the valve has not failed, it could be that the it is clogged. Take the valve apart - you should be able to remove 4 screws from the body of the valve without losing coolant (some say leave the coolant cap on to maintain a vacuum, Bentley says clamp the heater hoses) and inspect it to see if the filter screen is clogged - that would explain no heat.

Other potential problem sources are the other sensors involved in the heating system: internal temperature sensor (by the hood release), heater core temperature sensor (left side of heater box; requires console removal I believe), and the temperature regulating control unit (the dial on the HVAC control panel; this controls the operation of the heater valve, as noted above). Bentley explains tests for each.

Worst case, check for fluid leaking into the passenger compartment - including coolant odor and fogging windows. This is a heater core failure, and even Bentley doesn't cover that repair.

Of course, be sure to check fuses 6 and 14.

I believe the "I have heat at low speed but not at high speed" problem is due to a broken fresh-air flapper door, discussed in this thread: http://www.mye28.com/viewtopic.php?t=55525

I'm an E28 newb, and just misdiagnosed a non-existent heater problem. I did however do my research. I just didn't understand how to operate my new E28 HVAC system until I read the manual. :roll:
tsmall07
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Post by tsmall07 »

thesalboy wrote: internal temperature sensor (by the hood release),
Interesting... I did disconnect that sensor because I didn't really think it did anything. :lol: It seemed like the heat went away gradually over a long period of time rather than suddenly, but I may have just made myself believe that. It isn't very likely that it could be caused by debris in the cooling system since I replace the fluid regularly, but it can't be ruled out. I have to replace the brake booster anyway so I'll take the heater valve apart while I'm doing it.

Now that I think about it, I did have constant heat for a while this summer, but now there is no heat.
tsmall07
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Post by tsmall07 »

So, I hadn't been driving the car for a few days because it has been cold. I drove it tonight because I had to for work and the heat worked completely normally. I didn't do anything to it... :dunno:
thesalboy
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Post by thesalboy »

Pick up a Bentley for $38 from Amazon. Test the sensors. Otheriwse, the heater valve may be clogged.
thesalboy
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Post by thesalboy »

Turns out my HVAC always blew hot. I suspected the heater valve. I bought the repair kit.

The valve in its stock location on a 528e, just below and to the left of the brake master cylinder.

Image

I removed it from the firewall (8mm I believe), which I recommend doing. It might otherwise be possible to get to the 4 top screws, but I doubt it. I had the head off, so no coolant worries for me, but I suggest leaving the cap on and tilting the hoses up carefully.

Here's the disassembled valve with the repair kit for comparison. In addition to the filter being totally clogged (PO put some stop leak in there that just sat in heaps of goo in the heater hoses - DON'T EVER USE THAT STUFF!), there was a pinhole in the bladder. Thus the valve cannot keep hot water out of the heater core, and thus hot air all the time.

Image

Notice the metal cylinder has three "gaps" or "notches" in its top ring. The MyE28 FAQ (http://www.mye28.com/viewtopic.php?t=17342) notes that you need to align the underside of the electrical connector on the square cap with a notch on the cylinder. I chose the one with the closest fit - the smallest one that is by itself. I didn't note how it was aligned when I disassembled it.

I now have cold and hot air.
BATESY
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Post by BATESY »

i had the same problem, i chased this problem for a coupld of weeks and couldnt figure it out at all, i did a thermostat even put apart the heater hoses around the heater valve and found plastic parts in the hoses, got it all back together nothing and finally read about these heater valves and replaced mine, while replacing found the thing rusty and the rubber piece torn. I guess this is big thing that happens to Mercedes Benz's too.

BATES
C.R. Krieger
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Post by C.R. Krieger »

BATESY wrote:i had the same problem, i chased this problem for a coupld of weeks and couldnt figure it out at all, i did a thermostat even put apart the heater hoses around the heater valve and found plastic parts in the hoses, got it all back together nothing and finally read about these heater valves and replaced mine, while replacing found the thing rusty and the rubber piece torn. I guess this is big thing that happens to Mercedes Benz's too.

BATES
Serves you right for not reading the Tech FAQ. :roll:
Gernot
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Re: NO HEAT!!!

Post by Gernot »

Hi there,
i recognized a simmilar problem some weeks ago and tried to fix it ... but as it is now really cold outside ... i only was able to test it today. ... but without success.

to the story: I had always hot air blowing out the vent. at least if driving the car. if the car runs in idle and the fan is on the temperature goes down and it gets whatever temp you choose on the thermostate cold.
So I read about the heat valve at the firewall and changed it ... but unfortunately not with the hoped success. the situation is still the same.

whatever temp you choose the hot air blows at drive speed but gets cold to freezing if the car runs at idle.
any suggestion on how to test the electircal system where the fault is. coul dbe the temp sensor or thermostat at the inside or the control ...

regards and thanks for your help
Gernot
slammin_e28
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Re: NO HEAT!!!

Post by slammin_e28 »

Gernot wrote:Hi there,
i recognized a simmilar problem some weeks ago and tried to fix it ... but as it is now really cold outside ... i only was able to test it today. ... but without success.

to the story: I had always hot air blowing out the vent. at least if driving the car. if the car runs in idle and the fan is on the temperature goes down and it gets whatever temp you choose on the thermostate cold.
So I read about the heat valve at the firewall and changed it ... but unfortunately not with the hoped success. the situation is still the same.

whatever temp you choose the hot air blows at drive speed but gets cold to freezing if the car runs at idle.
any suggestion on how to test the electircal system where the fault is. coul dbe the temp sensor or thermostat at the inside or the control ...

regards and thanks for your help
Gernot
So you rebuilt the heater valve?

Most of the kits (MTC in particular) for doing that are absolute crap.
Gernot
Posts: 57
Joined: Aug 24, 2015 12:44 AM
Location: Stuttgart / Germany

Re: NO HEAT!!!

Post by Gernot »

sorry for the late answer.
I replaced the heater valve to a new ebay one. As this is not really helping i neet to investigate if the signal at the heating valve is on at what condition of the temperature switch.

As far as i know there must be power at the heater valve if the heater valve should be closed "no heating". someone to confirm that?

I will come back with the story ...
PA3
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Re: NO HEAT!!!

Post by PA3 »

Mine is doing the same. Replaced the valve and it was very toasty for a while. I stopped and left the engine idling for about 5 minutes then started on my way. Frpm then on, nothing but cool air. Pulled into the driveway and it got hot again. Cant figure it out...
Gernot
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Re: NO HEAT!!!

Post by Gernot »

PA3 wrote:Mine is doing the same. Replaced the valve and it was very toasty for a while. I stopped and left the engine idling for about 5 minutes then started on my way. Frpm then on, nothing but cool air. Pulled into the driveway and it got hot again. Cant figure it out...

did you check the system on the electrical side? found some checking process on the technical documentation. Had no time to check it really but found out that depending if the thermostat was switched on cold or heat before starting the engine makes an affect if the system is cold or hot.
Gernot
Posts: 57
Joined: Aug 24, 2015 12:44 AM
Location: Stuttgart / Germany

Re: NO HEAT!!!

Post by Gernot »

Hello,
as it is getting cold again ... what surprise I am on figuring out the heating problem.
I checked the valve but it works so next is the temperature sensor down on the driver side #10 on the picture http://bmwfans.info/parts-catalog/E28/E ... nts_heater

As i measured the sensor I got wired feedback
Pin 1-3
normal temperature 68F ~44Ohm
out of the fridge 46F ~41Ohm

As this sensor for a aircon 528 is about 200$ id like to confirm first that it is broken. So can someone confirm the figures I got or better tell me what he is measuring?

Thank's a lot for the help
Gernot
foamy
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Re: NO HEAT!!!

Post by foamy »

i installed a ball valve inline with the 2 hoses that ran to the heater valve 2 years ago. i know it was cold i wanted heat and had a ball valve handy.
Gernot
Posts: 57
Joined: Aug 24, 2015 12:44 AM
Location: Stuttgart / Germany

Re: NO HEAT!!!

Post by Gernot »

Gernot wrote:Hello,
as it is getting cold again ... what surprise I am on figuring out the heating problem.
I checked the valve but it works so next is the temperature sensor down on the driver side #10 on the picture http://bmwfans.info/parts-catalog/E28/E ... nts_heater

As i measured the sensor I got wired feedback
Pin 1-3
normal temperature 68F ~44Ohm
out of the fridge 46F ~41Ohm

As this sensor for a aircon 528 is about 200$ id like to confirm first that it is broken. So can someone confirm the figures I got or better tell me what he is measuring?

Thank's a lot for the help
Gernot
ImageImage
Shockwave
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Location: Canada

Re: NO HEAT!!!

Post by Shockwave »

Just to add to the information in this thread for anyone searching for information in the future, I had two separate problems which prevented my car from getting heat:

The fuse for the heater fan wasn't blown, but it was deformed and melted at each end, and there was carbon build up as well, all due to the use of cheap plastic fuses. Brushing the fuse posts and replacing the fuse fixed the fan... but I still had no heat in the cabin at any speed.

The culprit was in fact the heater valve. The valve had failed in such a way as to block coolant flow into the heater core. Removing the top cover of the valve and pulling the inner components revealed a badly ripped diaphragm. I've left the valve gutted as a bypass, and will replace the contents in the spring. :)
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