Ford Fiesta Mk4 Heater Only Works On Cold Sometimes On Hot But Normally Cold Only The Temp Gauge Reads Ok

How do chief , I had a similar problem on a '96 Fiesta Courier , in my case it turned out to be the heater control valve sticking in one position . You can find this valve under the bonnet in the bulkhead area plumbed into coolant pipes with an electrical connection to it . Somebody who knows more than I do will tell you how to go about getting it replaced . Hope this helps .

Regards ,
Plasticpat .