The cable that is operated by the dash panel slider, the one that switches from heater to AC, has snapped off under the dash where it meets the blower case.I am trying to find a way to switch from heat to AC, as summer is coming and the car is uncomfortably hot.Does anyone know a way to bypass that cable and manually switch the control? Or can anyone tell me where to find a detailed schematic of the blower case and how it operates? The diagram in my Haynes manual shows the parts but is useless as far as explaining the operation. My car is a 1978 244DL, with less than 100,000 original miles and I would hate to have to get rid of it for this reason. Thanks in advance for any possible help

 

Pull the driver's side center console kick panel and take another look. The slider cable goes to the heater valve control. It's behind the blower case against the firewall. You have either a rocker switch or round **** that engages the compressor. The cable that broke is clamped to the heater valve by a screw. You may have enough slack in the existing cable to reattach it. If not, the cables were virtually unchanged for the entire model run. Finding one at the JY should be simple.

 

First, thank you so much for the quick reply, SJ.
I must clarify the problem. It is not the cable itself that is broken. It is the lever like terminus that snapped off the box that I assume is what you called the heater control valve. It seems to be a lever pressed onto a cylinder shaped metal dowel that stands in a metal box... a very tight space to see or work in. So I guess my next questions are:
1) Is there any way to operate this control valve without the cable?, or,
2) Assuming I can get one at a junkyard or find a new part, can it be replaced, or do I have to change the whole blower case ? I can handle a one or two hundred dollar repair bill but I can't really put more than that into the car at this point. I would have to either take the car off the road for the summer or sell it and find something else, which I would really hate to do. The mileage is not yet 100,000 and I think the car has years of life in it.

 

I should have also told you that the compressor is engaging. What I think is the actual problem is that a door or shutter that is supposed to open or close ( I think thats how the system on an old American car works) is not moving. For the last couple of years, as the seasons changes, I would have to get under the dash and give that little lever at the end of the cable an extra push to go to AC in the spring , and then a pull to go back to heat in the fall. The compressor is engaing when I have the slide control to the left on cool, but the fan is blowing hot air through the vents. The compressor is definitely good, I have gone through this for three years. But now with that little lever popped off I cannot help the cable operate that valve.
Thanks again for your help.

 

Quick synopsis on how early 240 a/c works. The compressor on many models runs essentially non-stop until (never happens) the expansion valve gets down to~38 degrees. The blower blows air through the evaporator and the heater core. So...the a/c removes as much jeat as it can and the cable that isn't working controls how much hot engine coolant goes thru the heater core. So, even though the a/c is working its best, the heater core when stuck to full warm , as yours apparently is, the unit will blow warm air. Volvo 240's are as famous for their marvelous heaters as they are infamous for the paltry a/c.
You have a couple of options. BTW, that lever is indeed the heater control valve; like a faucet, it controls how much coolant flows through the heater core. First, replace the heater control valve. As you have seen, it is sandwiched between the blower case and the firewall. While not the best of locations, it isn't neccessary or even recommended to remove the blower case. Replacing the heater valve is done by feel as much as anything. Here at the shop, being pro's, we bill 1 hour labor ($80) for the job. Replacing the valve is the "correct" thing to do in as much as it will allow the system to operate with the controls on the panel.
In the short term, you can simply move the heater control valve either with your fingers or perhaps a pair of pliers, to the off position. You'll need to experiment to determine which direction is off. A second solution, often used when the heater core is leaking, is remove the 2 heater hoses in the engine compartment coming from the head and the metal pipe that runs along side the block from the water pump. Just connect a single hose to the two outlets. This keeps all heated coolant from entering the heater core. But...you'll have to swap the original hoses back in next fall.
Your best bet is to at least move the lever, if not install a new heater valve. Should you decide to replace the heater valve, spend the extra money for an all metal one. For some years, the only replacement was half metal/half plastic and it didn't usually hold up very long. IPD.com has the all metal valves.
Also. an immediate band-aid fix would be to simply clamp shut one of the two heater hoses at the firewall in the engine bay. You'd need to use flat jawed hose clamping pliers to avoid damaging the hose...Harbor Freight has them for ~$5.

 

Thank you SwiftJustice for the good news. I spoke to KarpVolvo, my nearest dealer, and they also recommended IPD for the older style all metal valve. My mechanic had suggested the hose connector heater core bypass that you mentioned, and I have a day or two this week to try to turn the valve with a needle nose before I give up on the DIY fix and surrender to the shop. But I am so happy with the info you have given me... even if the labor goes a little higher than your estimate of an hour for the job, the price of the valve was quoted at around $75 so I am going to be able to afford to have the job done right and I can hopefully get several more years out of the car.

 

Hey, that's great news!