AC problem

[Guest plym69]

The ac on my 1989 tc Runs cold but periodically it seems like the vent closes - the fan keeps running but no air comes out -then after about a minutes the vents seem to open and all is normal again. This goes on and on like this. Any ideas?

[ghostymosty]

I'm guessing the air stops coming out of the front vents and starts coming out of the defroster vents which are the default.

[Guest pizzaman7880]

When you accelerate you loose vacuum and the air flow door closes and diverts the air to the defroster. This is as David said is by default.

There is a check valve in the vacuum lines that is supposed to minimize this. I replaced all of the vacuum lines and check valves in one of mine and it really made a big difference.

Good luck

[89TC-16V]

sounds like its low on refridgerant just a thought

[Guest MiamiTVR]

This is a common problem in older Volvos. I am not a mechanic but seem to recall the fix for them is to replace the brain (or system) that controls the flaps and that the piece had a number of air lines attached that ran to those flaps opening and closing them as needed when things worked right and not doing so when they did not.

[Bill Reichert]

Ditto

When you accelerate you loose vacuum and the air flow door closes and diverts the air to the defroster. This is as David said is by default.

There is a check valve in the vacuum lines that is supposed to minimize this. I replaced all of the vacuum lines and check valves in one of mine and it really made a big difference.

Good luck

[Guest My TC Toy]

Those answers sound realistic. Most likely the culprit is the vacuum selector switch in the heater control. There is no maintenance that can be done on the switch and the do no last forever.

[Hemi Dude]

This is a common problem in older Volvos. I am not a mechanic but seem to recall the fix for them is to replace the brain (or system) that controls the flaps and that the piece had a number of air lines attached that ran to those flaps opening and closing them as needed when things worked right and not doing so when they did not.

Lucky thing there is no brain in a TC. (that could be possible even with a driver behind the wheel)

There is a vacuum actuator, actually there are several but the one closest to the accelerator pedal, up under the dash on the HVAC unit is the one I'm referring to. It controls this operation and there is a good possibility that the diaphragm has developed a leak. They are replaceable, but difficult to do.

The check valve should be the first thing to check and likely replace.

[Rob221]

plym69 I had the same problem.Replaced the check valve.Now it works like it should.Replace the Check valve.

[Guest plym69]

Hi Robb 221 Which heater check valve and where is it located? Sorry, I'm new at this. Thanks Ken

[Rob221]

Hi plym69 sent you email.Let me know if you get it or if you have any problems.

[Rob221]

Here is a picture of the Vacuum check valve

[4 Peaks]

plym69,your loosing vacuum, check all lines from vacuum source and all connections, one way valve, function switch and air control door vacuum actuator.

[gymowner]

mine does this constantly and only when i need extra acceleration or "boost" from the engine. after about 10 seconds it settles down and air blows again on the upper vents... until i need extra engine oomph then is cycles this issue over and over.

 

rob221.... that picture looks like it is somewhere in the engine bay yet i cannot seem to find a check valve there like this. can you take a larger pic of this area so i can look in my engine bay for the valve?

[Hemi Dude]

1 hour ago, gymowner said:

mine does this constantly and only when i need extra acceleration or "boost" from the engine. after about 10 seconds it settles down and air blows again on the upper vents... until i need extra engine oomph then is cycles this issue over and over.

 

If you read what I wrote May 16 2012 (above) and suspect this is the problem, PM me

[Red Alf]

Mr. Hemi, can you please suggest how to remove/replace the vacuum actuator that you mentioned above.

Thanks

[gymowner]

im gonna work on the vacuum actuator on my '89 TC. air is cold but as i stated above there is the vent door issue. a vacuum drop as stated in the manual can also make the car idle slightly rough as does mine when the ac compressor is on. if the car has the ac on and i put it in park it then idles fine. if i put the car in park when no ac is on after the engine is warm, then the idle wants to go up to about 1500 rpms. something for sure with vacuum pressure issue.

 

im selling this car. re-painted a really cool italian medium/deep green and with a haartz black cloth soft top and ginger interior it looks fantastic. i also added the smec unit from daytona (plug and play)and a Porsche blow off valve with added about 40 ponies. 

 

only reason in selling my baby is i finally had the opportunity of purchasing #386 of the 501 manuals made. and with inly 3150 miles at purchase this month!  it is as new. if there is an area to list on here for sale i will offer there. if anyone knows of a potential buyer please get in touch with me,  john  at 815 258-3422. the car is in las vegas. i hope i am not breaking any rules here for posting. if so i will take this down immediately.