I found the Vacuum Controller and noticed a clicking noise when I moved the wires around a little. Pinching a couple of the tubes changes which vent the air flowed from, and at one point it seemed as if some heat came in, but never really full on.

So I pulled it and it looks like there might be some damage. Some solder points look like they've been played with before, and one of the six vacuum ports has black marks, like something was scorched or shorted.

Mik Muller - VacuumController 1
Mik Muller - VacuumController 2
Mik Muller - VacuumController 3

So I just ordered a new one (part number 1388199) from a local parts place for $215, delivered (I know it's $10 more than the online parts place you recommended, but these guys are local and I want to start developing a relationship with them -- this will not be the last tie I will need parts). Should be here on Monday.

 

Actually, these guys have used ones, too.

Volvo V90 Solenoid Valve (Vaccuum line control unit)

 

Or new from Tasca Volvo Volvo Parts - TascaParts.com

A bad Vacuum Controller still does not explain that the Blend Door (or Air Mix Door) is stuck not opening to the Heater Core. This door is operated by the Servomotor, which is fully controlled by the ECC.

In addition, throwing random codes means that something is awry at the ECC.

Sorry to rain on your parade, but I would still check the ECC. Again, this is the link to instructions on how to remove it https://volvoforums.com/forum/volvo-...ulb-out-42248/ .

 

Arg. Well, the brand new Vacuum Controller did, in fact, NOT fix the problem. Thanks for the rain!

I pulled the ECC but do not see where any problems might be, as it's simply just two wire harness ports.

Mik Muller - ECC Rear

I'm hesitant to buy a replacement for this. Are there any tests I can do?

BTW, when I replaced the Vacuum Controller and the hose harness was hanging unconnected, there was only one hose that was pulling. The rest were dormant.

 

New Vacuum Controller means reliable defrost in the winter and reliable Heater Valve operation (closing) in the summer.


Open the ECC and as we said before, get a magnifying glass and check for cracks in the solder points. Re-flow some solder in the cracked/questionable joints. Just like the other person had done at the Vacuum Controller.

Throwing those two codes (132 and 161) is not that random. They might pinpoint which specific joints you should check. As you can see in this Wiring Diagram, code 132 points to joints-relative to terminals B1 and B2, and code 161 points to terminals B7 and B8 on the ECC. Five Servomotor connections are to terminals A17, A18, A27, A28, A29. If any of these has a crack you will have an inoperative Servomotor. Trace these terminals into the respective solder joints and check these first.

Again Servomotor is the device that operates that Blend Door (Air Mix). When you select "Heat" on the ECC, ECC needs to command the Servomotor to divert air into the Heater Core. Blower works, there is hot coolant in the Core, you just need the airflow to be directed to it, so you can have heat.


Correct, you should only have Vacuum in the "Supply" hose.

 

I opened the ECC last night and pulled up the board for a closer look. It looks brand new inside. The board is pristine. The jacks are firm and don't wiggle.

Could it be that the Blend Door is just jammed? The ECC works fine for all other purposes... just doesn't send heat.

Also, now that the dome light is back in and the hose reattached to the sensor, I can't get the AC light to provide any codes. It still blinks, but no matter what I do I can't get it to provide the codes anymore. Bizarre.

 

Ok. I opened the ECC again, got out the soldering gun, and "re-flowed" points B1, B2, B7 and B8. Still no heat, but now the face vents won't come on. This happened periodically in the past as well, so perhaps the ECC needs replacing.

I'm thinking of hiring a local mechanic to simply lock the Blend Door open for the winter.

 

Sure you can let a mechanic whack you, but I wouldn't jump that gun just yet.

Like I mentioned on my previous comment, B terminals you flowed are related to the 2 sensors, NOT Servomotor. Re-read my previous message about which A terminals to trace to the board, and re-flow these.

Your symptoms though are similar to having a bad chassis ground on the ECC. Lemme explain -- as you probably saw from the Wiring Diagram I sent you, there is only one ground to the entire ECC. The way they wire these Control Units is to use the chassis (ECC chassis in your case) to ground other circuits.

Servomotor is a motor, and it requires a 12V and a Ground, as minimum. These are A17 and A18. Measure across these two terminals at the ECC fully connected, and with engine warm and Temp Selector at Heat. You should pay attention to these specifics and follow them.

If all the above conditions are met, you should see 12V at A17 and A18. If not, measure across other Servomotor terminals at the ECC.

You already have the Parts Blowout (posted earlier), so you should be able to see the servomotor. If the electrical test does not succeed, try to move the arm gently - do not force it.

Blend Door might be jammed (unlikely), or shaft might be disconnected (unlikely), or even the Servomotor might be bad (unlikely). None of these would explain the ECC being screwy.

About the face vents not coming on -- all controlled by the ECC.

 

So, just because I was running short on time, I pulled the servo motor and used a wire to hold the door open. Full heat is back. I'll take the time to do further diagnosis after the holidays.

 

Good to hear.