When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
It’s getting cold here so go to slide temp lever from cold to hot and about 3/4 the way it snaps. I got a new control unit and go to test with temp control cable connected. It doesn’t bind/stop like before but when going to the full cold position, the lever wants to move back. Even after adjusting the cable adjuster and lubing the vacuum hot water valve switch, when I move the temp lever to the full cold position and let go it moves back about an inch and I can see the vacuum hot water switch is pushing it back. Will the VHW switch function differently with engine/vacuum running? I also notice a split in the cable near the mounting point on top the heater box so have a new one ordered. When a manually push the VHWS in it has some resistance but nothing tight but enough to push the cable back.
Hard to believe that little vacuum switch with its really light spring could push the cable back. I'm thinking that the issue is with the cable itself.
Hard to believe that little vacuum switch with its really light spring could push the cable back. I'm thinking that the issue is with the cable itself.
Hey Doc, If this car is a 77 - 79 this is a known issue with the imported switches. The internal spring on these is over twice the original strength as the factory switches. We need more information to diagnose this issue.
No doubt, I do remember hearing of issues with aftermarket vacuum switches. With the ridiculously strong spring.
I still have the factory switch in mine. Although it hasn't been connected in years. Not much need for a heater here.
When a manually push the VHWS in it has some resistance but nothing tight but enough to push the cable back.
A black plunger indicates you probably have an original switch. The factory switches came in at around 3 1/2 to 4 lbs. You can check yours by pushing it down plunger first against a scale designed for a light load like a postage scale. I've seen original switches with all kinds of issues internally, yours may be bad. In my opinion the switch spring is only to move the internal shuttle between the 2 vacuum ports and not to return the cable. Your cable could also be your problem.
Many, many years ago I replaced the original switch with a reproduction switch.
The spring in the replacement was way to strong and the Cold/Hot slider lever would not hold at cold...
This is what I did...
Vacuum hot water switch
