May one fix a car on Chol Hamoed?
It is permitted to fix a car on Chol Hamoed. However, it is only permitted to do so for the sake of using the car for the sake of the Moed. Likewise, it is only permitted to do so if the fixing is defined as Maaseh Hedyot, which means that it can be performed by any amateur and does not require a professional [such as to change a flat tire]. It is however forbidden to perform a fixing that is defined as Maaseh Uman, professional work, even if it is for the sake of the Moed, unless one of the listed exceptions of Maaseh Uman is applicable. One may not fix a car even with Maaseh Hedyot, for the sake of traveling from Eretz Yisrael to the Diaspora. Thus, one may not fix a flat tire for the sake of traveling to Eilat.
 Michaber 536:1
 Michaber ibid regarding fixing an animal for the ride
 M”B 536:2 in name of Beis Yosef; See P”M 536 A”A 1 that it is forbidden to fix the animal for the sake of traveling for monetary purposes; Chol Hamoed Kehilchasa Tikkunim 266; Piskeiy Teshuvos 536:1 footnote 1
 Piskeiy Teshuvos 536:1; Chol Hamoed Kehilchasa ibid
 Chol Hamoed Kehilchaso 7:76
 M”A 536:1
 Chol Hamoed Kehilchasa 7:79