Heater not working

[cjfman]

As the title says, the heat doesn't seem to be working. The fan works just fine, as does the AC. Blows nice and cold. When engaging the AC, I can hear various vents opening and closing as expected. The engine cooling system seems to be working just fine, as I don't have any overheating problems. I believe the thermostat is working. I pulled the control wires off of the heater valve to test this. When the thermostat was turned all the way up, no voltage was applied. When turned all the way down, voltage was applied to close the valve ex expected. The e28 maintenance manual says that the heater valve is normally open should click when it's activated. I tested this by plugging and unplugging the control wires. It does click, but not very loudly. The coolant tubes leading to the valve were warm, hot. Any ideas?

[bmw6fan]

Is the fan motor under the hood running for the heater?

[cjfman]

Yeah. All the fans run. The heater does blow fresh air, it’s just not hot.

[1986series6]

From your description sounds like the heater control valve is the problem.
Take it apart, if the diaphragm is good clean & lube the piston.
If not order the best rebuild kit you can find.

Don't be fooled with this garbage, you'll be repairing it again.

https://www.amazon.com/BMW-OEM-Mono-.../dp/B010A9NC0A

Use this one and you'll be good for the next 10 years if not more.

https://www.pelicanparts.com/More_In...assCat=Y&null=

[cjfman]

Cool. I’m hoping it’s just the valve. I doubt it’s the heat core since the AC works and I can hear all of the flaps open and close. I’ve never drained the coolant myself before, so I’m not really looking forward to that. I may be able to just clamp off the hoses around the pump, but I don’t know how brittle they are. Will check and report back.

[DesktopDave]

+1 on the heater valve seal, it's a common problem. Those heater lines are not highly-pressurized, they rarely crack, it's easy to clamp them shut. Space is a little tight though. If you haven't flushed the system in a while, I'd recommend cracking the bleeder screw open first, just to be sure it works before you open anything else.

Bleeding the system is important, take your time. I prefer to park the car uphill or on some ramps, it helps a lot.

[ldk]

I don't know how long you've owned the car. Has the heater ever worked for you? I had the same issue as you, and I ended up needing to replace the heater core. I hope the valve replacement works for you.

[cjfman]

I've ordered a new valve. Will need to go buy some clamps. I love buying tools. The heat's never worked as long I've owned it since April. The previous owner lived in San Diego and probably just never noticed. I'm surprised the inspection team didn't catch it. They caught a transmission and differential oil leak, but somehow managed to miss the reverse light and heater. Go fig. Thank for the help guys! I will report back when I swap out the valve.

[parkerbomar]

Here is a quick and cheap way to fix it and never deal with the OEM garbage again.

http://bigcoupe.com/phpBB2/viewtopic.php?f=2&t=31889

[cjfman]

Ok, so I've got the heat working again. I bought a new heater valve. I accidentally bought one with a bent outlet, but I was able to swap the electro-mechanical insides with the original. The valve seal didn't look too bad, but the whole mechanism was kind of crusty and was hard to pull out. Maybe it got stuck. Either way, the "new" valve works like a charm. For a moment I thought I hadn't fixed it, but then someone reminded me that heat only comes out of the footwell and defroster. I was afraid that I didn't need to change it at all until I remembered that my mechanic confirmed that the heat didn't work. Also, there was no coolant in the outlet of the old valve.

[DesktopDave]

Glad you've fixed it, thanks for the follow up.

Yeah, our cars are fun like that, the 'cold-only' middle vents were an odd choice. The split heater & A/C systems on these cars are a throwback system, that's for sure!

[Sowhatsg]

Hello, I also need to replace the heater valve or fix it. I don’t have a lot of mechanic experience. Did you lose a lot of coolant when unplugging the pipes? What type of clamp did you use? Do you just have to top up coolant after replacement, run the car and top again until all air is gone? Thanks!