Worth noting that many of the Carver heating products were Truma built under licence.
In 1967 Carver first started importing and selling complete Truma heaters. Throughout the next decade, that changed to Carver assembling CkD kits of Truma products. Progressively Carver began manufacturing parts for the heaters, to increase local content, and to Anglicise them for the UK market. The licence only came in when Carver negotiated to assemble the two heat exchanger halves from Truma supplied castings. The companies agreed that Carver should serve the UK, and Truma the rest of the world.
In the late 80's the EU competition regulations took an interest, and told both companies the arrangement needed to change, and effectively it pitched both companies into competition rather than cooperation. Carver had to set about completely redesigning the space heaters to by wholly designed and manufactured by Carver. This included all the castings, and burner and valve gear.
There were natural similarities in the products because they had to do the same job, and fit in caravans in much the same way, but there were no common parts by 1997. About the only part that could be interchanged was the hot air ducting.
So for the OP and his 1999 caravan if it has any Carver Products, they are totally Carver not Truma.
Carver confirmed it's independence, by introducing the first room sealed storage water heater for touring caravans, the Cascade (MK1)in 1980. it later produced the Crystal water systems, and the Cascade II,(1984) then in the early 90's it developed the first Caravan Mover which drove the road wheels.
These were all products that Truma either wanted or threatened market share.
During the 90's the UK touring caravan market was shrinking, down to about 50% on its 80's peak. Having two major suppliers after a dwindling number of customers was going to be difficult, Carver decided to sell it's leisure business to Truma, but continues to have other business interests around the world.
After the acquisition, Truma renamed the Carver leisure business as Carver Technology. But completely closed the business after 6 months. Truma has continued and developed some of the unique Carver products under their own name, but the heating appliances were quickly removed from sale. They continued to manufacture a limited range of spare parts, but over the 23 years even some of these are now completely finished.