Heating Problems

[Jimmy535i]

I need some troubleshooting advice on cabin heating systems.

I am having problems with my 1992 535i. It appears
that the AC runs and will not switch to heat.

I recently converted my AC system to r-134a and the AC
system blows ice cold.

My problems started with what i thought was a bad auxillary fan resistor.
The fuse blew and when I tried to replace the fuse the auxillary fan resistor fried. I replaced the resistor and now the AC runs but the heat
will not come on.

Can someone advise on how to troubleshoot this problem.

I purchased a replacement HVAC control panel on ebay this weekend. Could this unit cause the problem?

[JonE]

The aux fan resistor shouldn't have anything to do with the heat. Suspects probably would be
1. not bled properly (is your temp guage at 12oclock?),
2. heater valve and/or auxillary pump problem. If the coolant is getting hot it will need to get to your heater core by way of the heater valve assembly.
3. does the heater/ac cabin fan work on all settings? If only comes on "high" then could be the resistor pack for the fan.
4. I'm not sure about the control panel functions.
You probably know about all of the above already, but just thought I'd mention them again.

[dternst]

Position the dial in the middle of the center vent to heat (red). Blue for cold and red for heat. I know it sounds simple but sometimes we overlook the simplest things.

David

[Jimmy535i]

Temp guage is dead center. Just changed water pump, coolant (bmw 50/50)
and fan clutch.

Fan blower is fine. It works at all speeds. I will look at heater valve and auxillary pump. Thanks

The aux fan resistor shouldn't have anything to do with the heat. Suspects probably would be
1. not bled properly (is your temp guage at 12oclock?),
2. heater valve and/or auxillary pump problem. If the coolant is getting hot it will need to get to your heater core by way of the heater valve assembly.
3. does the heater/ac cabin fan work on all settings? If only comes on "high" then could be the resistor pack for the fan.
4. I'm not sure about the control panel functions.
You probably know about all of the above already, but just thought I'd mention them again.

[Jimmy535i]

Thanks Dave. I will try that also.

[Ted K]

How do you check the heater valve and/or auxillary pump?

[winfred]

shoot power to it, the pump is just two wires and the valves have a 3 wires, the one pin that further from the firewall hook power to that and ground one of the two rearward pins, there should be a click when you ground ether rear pin, no click on one side wack it with a hunk of wood and try again

How do you check the heater valve and/or auxillary pump?

[shogun]

The simplest way to check is just remove the power plug from top of the heater valves.
No power = valves should be fully open.

If no heat goes thru, give the valves a wack with the handle of a big screwdriver. Sometimes they are stuck and this could loosen them.

Here some good info from Johan's page

[Paul in NZ]

wack it with a hunk of wood and try again

give the valves a wack with the handle of a big screwdriver.

Did you guys go to the same auto school?

[shogun]

but that is top of the notch backyard hack mechanic university knowledge

Or actually just learning by doing.